diff --git a/docs/tests.md b/docs/tests.md
index d6736080..2ab67659 100644
--- a/docs/tests.md
+++ b/docs/tests.md
@@ -81,8 +81,10 @@ These checks validate various qualities like runtime execution, building process
     - [`Stubs/`](./../tests/unit/shared/Stubs): Maintains stubs for component isolation, equipped with basic functionalities and, when necessary, spying or mocking capabilities.
 - [`./tests/integration/`](./../tests/integration/): Contains integration test files.
 - [`cypress.config.ts`](./../cypress.config.ts): Cypress (E2E tests) configuration file.
+- [`cypress-dirs.json`](./../cypress-dirs.json): A central definition of directories used by Cypress, designed for reuse across different configurations.
 - [`./tests/e2e/`](./../tests/e2e/): Base Cypress folder, includes tests with `.cy.ts` extension.
-  - [`/support/e2e.ts`](./../tests/e2e/support/e2e.ts): Support file, runs before every single spec file.
   - [`/tsconfig.json`]: TypeScript configuration for file Cypress code, improves IDE support, recommended to have by official documentation.
   - *(git ignored)* `/videos`: Asset folder for videos taken during tests.
   - *(git ignored)* `/screenshots`: Asset folder for Screenshots taken during tests.
+  - [`/support/e2e.ts`](./../tests/e2e/support/e2e.ts): Support file, runs before every single test file.
+  - [`/support/interactions/`](./../tests/e2e/support/interactions/): Contains reusable functions for simulating user interactions, enhancing test readability and maintainability.
diff --git a/src/application/Common/Timing/BatchedDebounce.ts b/src/application/Common/Timing/BatchedDebounce.ts
new file mode 100644
index 00000000..6eb69cd1
--- /dev/null
+++ b/src/application/Common/Timing/BatchedDebounce.ts
@@ -0,0 +1,27 @@
+import { PlatformTimer } from './PlatformTimer';
+import { TimeoutType, Timer } from './Timer';
+
+export function batchedDebounce<T>(
+  callback: (batches: readonly T[]) => void,
+  waitInMs: number,
+  timer: Timer = PlatformTimer,
+): (arg: T) => void {
+  let lastTimeoutId: TimeoutType | undefined;
+  let batches: Array<T> = [];
+
+  return (arg: T) => {
+    batches.push(arg);
+
+    const later = () => {
+      callback(batches);
+      batches = [];
+      lastTimeoutId = undefined;
+    };
+
+    if (lastTimeoutId !== undefined) {
+      timer.clearTimeout(lastTimeoutId);
+    }
+
+    lastTimeoutId = timer.setTimeout(later, waitInMs);
+  };
+}
diff --git a/src/application/Common/Timing/PlatformTimer.ts b/src/application/Common/Timing/PlatformTimer.ts
new file mode 100644
index 00000000..101d5203
--- /dev/null
+++ b/src/application/Common/Timing/PlatformTimer.ts
@@ -0,0 +1,7 @@
+import { Timer } from './Timer';
+
+export const PlatformTimer: Timer = {
+  setTimeout: (callback, ms) => setTimeout(callback, ms),
+  clearTimeout: (timeoutId) => clearTimeout(timeoutId),
+  dateNow: () => Date.now(),
+};
diff --git a/src/presentation/components/Shared/Throttle.ts b/src/application/Common/Timing/Throttle.ts
similarity index 63%
rename from src/presentation/components/Shared/Throttle.ts
rename to src/application/Common/Timing/Throttle.ts
index 87f8d948..74102fb4 100644
--- a/src/presentation/components/Shared/Throttle.ts
+++ b/src/application/Common/Timing/Throttle.ts
@@ -1,40 +1,24 @@
+import { Timer, TimeoutType } from './Timer';
+import { PlatformTimer } from './PlatformTimer';
+
 export type CallbackType = (..._: unknown[]) => void;
 
 export function throttle(
   callback: CallbackType,
   waitInMs: number,
-  timer: ITimer = NodeTimer,
+  timer: Timer = PlatformTimer,
 ): CallbackType {
   const throttler = new Throttler(timer, waitInMs, callback);
   return (...args: unknown[]) => throttler.invoke(...args);
 }
 
-// Allows aligning with both NodeJs (NodeJs.Timeout) and Window type (number)
-export type Timeout = ReturnType<typeof setTimeout>;
-
-export interface ITimer {
-  setTimeout: (callback: () => void, ms: number) => Timeout;
-  clearTimeout: (timeoutId: Timeout) => void;
-  dateNow(): number;
-}
-
-const NodeTimer: ITimer = {
-  setTimeout: (callback, ms) => setTimeout(callback, ms),
-  clearTimeout: (timeoutId) => clearTimeout(timeoutId),
-  dateNow: () => Date.now(),
-};
-
-interface IThrottler {
-  invoke: CallbackType;
-}
-
-class Throttler implements IThrottler {
-  private queuedExecutionId: Timeout | undefined;
+class Throttler {
+  private queuedExecutionId: TimeoutType | undefined;
 
   private previouslyRun: number;
 
   constructor(
-    private readonly timer: ITimer,
+    private readonly timer: Timer,
     private readonly waitInMs: number,
     private readonly callback: CallbackType,
   ) {
diff --git a/src/application/Common/Timing/Timer.ts b/src/application/Common/Timing/Timer.ts
new file mode 100644
index 00000000..fe23b612
--- /dev/null
+++ b/src/application/Common/Timing/Timer.ts
@@ -0,0 +1,8 @@
+// Allows aligning with both NodeJs (NodeJs.Timeout) and Window type (number)
+export type TimeoutType = ReturnType<typeof setTimeout>;
+
+export interface Timer {
+  setTimeout: (callback: () => void, ms: number) => TimeoutType;
+  clearTimeout: (timeoutId: TimeoutType) => void;
+  dateNow(): number;
+}
diff --git a/src/application/Context/State/CategoryCollectionState.ts b/src/application/Context/State/CategoryCollectionState.ts
index da692d11..09efaf3a 100644
--- a/src/application/Context/State/CategoryCollectionState.ts
+++ b/src/application/Context/State/CategoryCollectionState.ts
@@ -4,23 +4,48 @@ import { UserFilter } from './Filter/UserFilter';
 import { IUserFilter } from './Filter/IUserFilter';
 import { ApplicationCode } from './Code/ApplicationCode';
 import { UserSelection } from './Selection/UserSelection';
-import { IUserSelection } from './Selection/IUserSelection';
 import { ICategoryCollectionState } from './ICategoryCollectionState';
 import { IApplicationCode } from './Code/IApplicationCode';
+import { UserSelectionFacade } from './Selection/UserSelectionFacade';
 
 export class CategoryCollectionState implements ICategoryCollectionState {
   public readonly os: OperatingSystem;
 
   public readonly code: IApplicationCode;
 
-  public readonly selection: IUserSelection;
+  public readonly selection: UserSelection;
 
   public readonly filter: IUserFilter;
 
-  public constructor(readonly collection: ICategoryCollection) {
-    this.selection = new UserSelection(collection, []);
-    this.code = new ApplicationCode(this.selection, collection.scripting);
-    this.filter = new UserFilter(collection);
+  public constructor(
+    public readonly collection: ICategoryCollection,
+    selectionFactory = DefaultSelectionFactory,
+    codeFactory = DefaultCodeFactory,
+    filterFactory = DefaultFilterFactory,
+  ) {
+    this.selection = selectionFactory(collection, []);
+    this.code = codeFactory(this.selection.scripts, collection.scripting);
+    this.filter = filterFactory(collection);
     this.os = collection.os;
   }
 }
+
+export type CodeFactory = (
+  ...params: ConstructorParameters<typeof ApplicationCode>
+) => IApplicationCode;
+
+const DefaultCodeFactory: CodeFactory = (...params) => new ApplicationCode(...params);
+
+export type SelectionFactory = (
+  ...params: ConstructorParameters<typeof UserSelectionFacade>
+) => UserSelection;
+
+const DefaultSelectionFactory: SelectionFactory = (
+  ...params
+) => new UserSelectionFacade(...params);
+
+export type FilterFactory = (
+  ...params: ConstructorParameters<typeof UserFilter>
+) => IUserFilter;
+
+const DefaultFilterFactory: FilterFactory = (...params) => new UserFilter(...params);
diff --git a/src/application/Context/State/Code/ApplicationCode.ts b/src/application/Context/State/Code/ApplicationCode.ts
index 91cf795f..a1c5d3f7 100644
--- a/src/application/Context/State/Code/ApplicationCode.ts
+++ b/src/application/Context/State/Code/ApplicationCode.ts
@@ -1,7 +1,7 @@
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
-import { IReadOnlyUserSelection } from '@/application/Context/State/Selection/IUserSelection';
 import { EventSource } from '@/infrastructure/Events/EventSource';
 import { IScriptingDefinition } from '@/domain/IScriptingDefinition';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
+import { ReadonlyScriptSelection } from '@/application/Context/State/Selection/Script/ScriptSelection';
 import { CodeChangedEvent } from './Event/CodeChangedEvent';
 import { CodePosition } from './Position/CodePosition';
 import { ICodeChangedEvent } from './Event/ICodeChangedEvent';
@@ -17,12 +17,12 @@ export class ApplicationCode implements IApplicationCode {
   private scriptPositions = new Map<SelectedScript, CodePosition>();
 
   constructor(
-    userSelection: IReadOnlyUserSelection,
+    selection: ReadonlyScriptSelection,
     private readonly scriptingDefinition: IScriptingDefinition,
     private readonly generator: IUserScriptGenerator = new UserScriptGenerator(),
   ) {
-    this.setCode(userSelection.selectedScripts);
-    userSelection.changed.on((scripts) => {
+    this.setCode(selection.selectedScripts);
+    selection.changed.on((scripts) => {
       this.setCode(scripts);
     });
   }
diff --git a/src/application/Context/State/Code/Event/CodeChangedEvent.ts b/src/application/Context/State/Code/Event/CodeChangedEvent.ts
index 681df926..0dbd6ca0 100644
--- a/src/application/Context/State/Code/Event/CodeChangedEvent.ts
+++ b/src/application/Context/State/Code/Event/CodeChangedEvent.ts
@@ -1,6 +1,6 @@
 import { IScript } from '@/domain/IScript';
 import { ICodePosition } from '@/application/Context/State/Code/Position/ICodePosition';
-import { SelectedScript } from '../../Selection/SelectedScript';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
 import { ICodeChangedEvent } from './ICodeChangedEvent';
 
 export class CodeChangedEvent implements ICodeChangedEvent {
@@ -36,7 +36,14 @@ export class CodeChangedEvent implements ICodeChangedEvent {
   }
 
   public getScriptPositionInCode(script: IScript): ICodePosition {
-    const position = this.scripts.get(script);
+    return this.getPositionById(script.id);
+  }
+
+  private getPositionById(scriptId: string): ICodePosition {
+    const position = [...this.scripts.entries()]
+      .filter(([s]) => s.id === scriptId)
+      .map(([, pos]) => pos)
+      .at(0);
     if (!position) {
       throw new Error('Unknown script: Position could not be found for the script');
     }
diff --git a/src/application/Context/State/Code/Event/ICodeChangedEvent.ts b/src/application/Context/State/Code/Event/ICodeChangedEvent.ts
index 570ebad8..ea05f0fb 100644
--- a/src/application/Context/State/Code/Event/ICodeChangedEvent.ts
+++ b/src/application/Context/State/Code/Event/ICodeChangedEvent.ts
@@ -3,9 +3,9 @@ import { ICodePosition } from '@/application/Context/State/Code/Position/ICodePo
 
 export interface ICodeChangedEvent {
   readonly code: string;
-  addedScripts: ReadonlyArray<IScript>;
-  removedScripts: ReadonlyArray<IScript>;
-  changedScripts: ReadonlyArray<IScript>;
+  readonly addedScripts: ReadonlyArray<IScript>;
+  readonly removedScripts: ReadonlyArray<IScript>;
+  readonly changedScripts: ReadonlyArray<IScript>;
   isEmpty(): boolean;
   getScriptPositionInCode(script: IScript): ICodePosition;
 }
diff --git a/src/application/Context/State/Code/Generation/IUserScript.ts b/src/application/Context/State/Code/Generation/IUserScript.ts
index 596819fd..0c1ef825 100644
--- a/src/application/Context/State/Code/Generation/IUserScript.ts
+++ b/src/application/Context/State/Code/Generation/IUserScript.ts
@@ -1,7 +1,7 @@
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
 import { ICodePosition } from '@/application/Context/State/Code/Position/ICodePosition';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
 
 export interface IUserScript {
-  code: string;
-  scriptPositions: Map<SelectedScript, ICodePosition>;
+  readonly code: string;
+  readonly scriptPositions: Map<SelectedScript, ICodePosition>;
 }
diff --git a/src/application/Context/State/Code/Generation/IUserScriptGenerator.ts b/src/application/Context/State/Code/Generation/IUserScriptGenerator.ts
index 23e47c90..808672f9 100644
--- a/src/application/Context/State/Code/Generation/IUserScriptGenerator.ts
+++ b/src/application/Context/State/Code/Generation/IUserScriptGenerator.ts
@@ -1,9 +1,10 @@
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
 import { IScriptingDefinition } from '@/domain/IScriptingDefinition';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
 import { IUserScript } from './IUserScript';
 
 export interface IUserScriptGenerator {
   buildCode(
     selectedScripts: ReadonlyArray<SelectedScript>,
-    scriptingDefinition: IScriptingDefinition): IUserScript;
+    scriptingDefinition: IScriptingDefinition,
+  ): IUserScript;
 }
diff --git a/src/application/Context/State/Code/Generation/UserScriptGenerator.ts b/src/application/Context/State/Code/Generation/UserScriptGenerator.ts
index e50b4a28..1cab63c3 100644
--- a/src/application/Context/State/Code/Generation/UserScriptGenerator.ts
+++ b/src/application/Context/State/Code/Generation/UserScriptGenerator.ts
@@ -1,6 +1,6 @@
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
 import { ICodePosition } from '@/application/Context/State/Code/Position/ICodePosition';
 import { IScriptingDefinition } from '@/domain/IScriptingDefinition';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
 import { CodePosition } from '../Position/CodePosition';
 import { IUserScriptGenerator } from './IUserScriptGenerator';
 import { IUserScript } from './IUserScript';
diff --git a/src/application/Context/State/ICategoryCollectionState.ts b/src/application/Context/State/ICategoryCollectionState.ts
index f07497e4..815aa413 100644
--- a/src/application/Context/State/ICategoryCollectionState.ts
+++ b/src/application/Context/State/ICategoryCollectionState.ts
@@ -1,18 +1,18 @@
 import { ICategoryCollection } from '@/domain/ICategoryCollection';
 import { OperatingSystem } from '@/domain/OperatingSystem';
 import { IReadOnlyUserFilter, IUserFilter } from './Filter/IUserFilter';
-import { IReadOnlyUserSelection, IUserSelection } from './Selection/IUserSelection';
+import { ReadonlyUserSelection, UserSelection } from './Selection/UserSelection';
 import { IApplicationCode } from './Code/IApplicationCode';
 
 export interface IReadOnlyCategoryCollectionState {
   readonly code: IApplicationCode;
   readonly os: OperatingSystem;
   readonly filter: IReadOnlyUserFilter;
-  readonly selection: IReadOnlyUserSelection;
+  readonly selection: ReadonlyUserSelection;
   readonly collection: ICategoryCollection;
 }
 
 export interface ICategoryCollectionState extends IReadOnlyCategoryCollectionState {
   readonly filter: IUserFilter;
-  readonly selection: IUserSelection;
+  readonly selection: UserSelection;
 }
diff --git a/src/application/Context/State/Selection/Category/CategorySelection.ts b/src/application/Context/State/Selection/Category/CategorySelection.ts
new file mode 100644
index 00000000..12fadc5f
--- /dev/null
+++ b/src/application/Context/State/Selection/Category/CategorySelection.ts
@@ -0,0 +1,11 @@
+import { ICategory } from '@/domain/ICategory';
+import { CategorySelectionChangeCommand } from './CategorySelectionChange';
+
+export interface ReadonlyCategorySelection {
+  areAllScriptsSelected(category: ICategory): boolean;
+  isAnyScriptSelected(category: ICategory): boolean;
+}
+
+export interface CategorySelection extends ReadonlyCategorySelection {
+  processChanges(action: CategorySelectionChangeCommand): void;
+}
diff --git a/src/application/Context/State/Selection/Category/CategorySelectionChange.ts b/src/application/Context/State/Selection/Category/CategorySelectionChange.ts
new file mode 100644
index 00000000..a944a3f6
--- /dev/null
+++ b/src/application/Context/State/Selection/Category/CategorySelectionChange.ts
@@ -0,0 +1,15 @@
+type CategorySelectionStatus = {
+  readonly isSelected: true;
+  readonly isReverted: boolean;
+} | {
+  readonly isSelected: false;
+};
+
+export interface CategorySelectionChange {
+  readonly categoryId: number;
+  readonly newStatus: CategorySelectionStatus;
+}
+
+export interface CategorySelectionChangeCommand {
+  readonly changes: readonly CategorySelectionChange[];
+}
diff --git a/src/application/Context/State/Selection/Category/ScriptToCategorySelectionMapper.ts b/src/application/Context/State/Selection/Category/ScriptToCategorySelectionMapper.ts
new file mode 100644
index 00000000..33667251
--- /dev/null
+++ b/src/application/Context/State/Selection/Category/ScriptToCategorySelectionMapper.ts
@@ -0,0 +1,60 @@
+import { ICategory } from '@/domain/ICategory';
+import { ICategoryCollection } from '@/domain/ICategoryCollection';
+import { ScriptSelection } from '../Script/ScriptSelection';
+import { ScriptSelectionChange } from '../Script/ScriptSelectionChange';
+import { CategorySelection } from './CategorySelection';
+import { CategorySelectionChange, CategorySelectionChangeCommand } from './CategorySelectionChange';
+
+export class ScriptToCategorySelectionMapper implements CategorySelection {
+  constructor(
+    private readonly scriptSelection: ScriptSelection,
+    private readonly collection: ICategoryCollection,
+  ) {
+
+  }
+
+  public areAllScriptsSelected(category: ICategory): boolean {
+    const { selectedScripts } = this.scriptSelection;
+    if (selectedScripts.length === 0) {
+      return false;
+    }
+    const scripts = category.getAllScriptsRecursively();
+    if (selectedScripts.length < scripts.length) {
+      return false;
+    }
+    return scripts.every(
+      (script) => selectedScripts.some((selected) => selected.id === script.id),
+    );
+  }
+
+  public isAnyScriptSelected(category: ICategory): boolean {
+    const { selectedScripts } = this.scriptSelection;
+    if (selectedScripts.length === 0) {
+      return false;
+    }
+    return selectedScripts.some((s) => category.includes(s.script));
+  }
+
+  public processChanges(action: CategorySelectionChangeCommand): void {
+    const scriptChanges = action.changes.reduce((changes, change) => {
+      changes.push(...this.collectScriptChanges(change));
+      return changes;
+    }, new Array<ScriptSelectionChange>());
+    this.scriptSelection.processChanges({
+      changes: scriptChanges,
+    });
+  }
+
+  private collectScriptChanges(change: CategorySelectionChange): ScriptSelectionChange[] {
+    const category = this.collection.getCategory(change.categoryId);
+    const scripts = category.getAllScriptsRecursively();
+    const scriptsChangesInCategory = scripts
+      .map((script): ScriptSelectionChange => ({
+        scriptId: script.id,
+        newStatus: {
+          ...change.newStatus,
+        },
+      }));
+    return scriptsChangesInCategory;
+  }
+}
diff --git a/src/application/Context/State/Selection/IUserSelection.ts b/src/application/Context/State/Selection/IUserSelection.ts
deleted file mode 100644
index b696bada..00000000
--- a/src/application/Context/State/Selection/IUserSelection.ts
+++ /dev/null
@@ -1,23 +0,0 @@
-import { IScript } from '@/domain/IScript';
-import { ICategory } from '@/domain/ICategory';
-import { IEventSource } from '@/infrastructure/Events/IEventSource';
-import { SelectedScript } from './SelectedScript';
-
-export interface IReadOnlyUserSelection {
-  readonly changed: IEventSource<ReadonlyArray<SelectedScript>>;
-  readonly selectedScripts: ReadonlyArray<SelectedScript>;
-  isSelected(scriptId: string): boolean;
-  areAllSelected(category: ICategory): boolean;
-  isAnySelected(category: ICategory): boolean;
-}
-
-export interface IUserSelection extends IReadOnlyUserSelection {
-  removeAllInCategory(categoryId: number): void;
-  addOrUpdateAllInCategory(categoryId: number, revert: boolean): void;
-  addSelectedScript(scriptId: string, revert: boolean): void;
-  addOrUpdateSelectedScript(scriptId: string, revert: boolean): void;
-  removeSelectedScript(scriptId: string): void;
-  selectOnly(scripts: ReadonlyArray<IScript>): void;
-  selectAll(): void;
-  deselectAll(): void;
-}
diff --git a/src/application/Context/State/Selection/Script/DebouncedScriptSelection.ts b/src/application/Context/State/Selection/Script/DebouncedScriptSelection.ts
new file mode 100644
index 00000000..ffe73762
--- /dev/null
+++ b/src/application/Context/State/Selection/Script/DebouncedScriptSelection.ts
@@ -0,0 +1,171 @@
+import { InMemoryRepository } from '@/infrastructure/Repository/InMemoryRepository';
+import { IScript } from '@/domain/IScript';
+import { EventSource } from '@/infrastructure/Events/EventSource';
+import { ReadonlyRepository, Repository } from '@/application/Repository/Repository';
+import { ICategoryCollection } from '@/domain/ICategoryCollection';
+import { batchedDebounce } from '@/application/Common/Timing/BatchedDebounce';
+import { ScriptSelection } from './ScriptSelection';
+import { ScriptSelectionChange, ScriptSelectionChangeCommand } from './ScriptSelectionChange';
+import { SelectedScript } from './SelectedScript';
+import { UserSelectedScript } from './UserSelectedScript';
+
+const DEBOUNCE_DELAY_IN_MS = 100;
+
+export type DebounceFunction = typeof batchedDebounce<ScriptSelectionChangeCommand>;
+
+export class DebouncedScriptSelection implements ScriptSelection {
+  public readonly changed = new EventSource<ReadonlyArray<SelectedScript>>();
+
+  private readonly scripts: Repository<string, SelectedScript>;
+
+  public readonly processChanges: ScriptSelection['processChanges'];
+
+  constructor(
+    private readonly collection: ICategoryCollection,
+    selectedScripts: ReadonlyArray<SelectedScript>,
+    debounce: DebounceFunction = batchedDebounce,
+  ) {
+    this.scripts = new InMemoryRepository<string, SelectedScript>();
+    for (const script of selectedScripts) {
+      this.scripts.addItem(script);
+    }
+    this.processChanges = debounce(
+      (batchedRequests: readonly ScriptSelectionChangeCommand[]) => {
+        const consolidatedChanges = batchedRequests.flatMap((request) => request.changes);
+        this.processScriptChanges(consolidatedChanges);
+      },
+      DEBOUNCE_DELAY_IN_MS,
+    );
+  }
+
+  public isSelected(scriptId: string): boolean {
+    return this.scripts.exists(scriptId);
+  }
+
+  public get selectedScripts(): readonly SelectedScript[] {
+    return this.scripts.getItems();
+  }
+
+  public selectAll(): void {
+    const scriptsToSelect = this.collection
+      .getAllScripts()
+      .filter((script) => !this.scripts.exists(script.id))
+      .map((script) => new UserSelectedScript(script, false));
+    if (scriptsToSelect.length === 0) {
+      return;
+    }
+    this.processChanges({
+      changes: scriptsToSelect.map((script): ScriptSelectionChange => ({
+        scriptId: script.id,
+        newStatus: {
+          isSelected: true,
+          isReverted: false,
+        },
+      })),
+    });
+  }
+
+  public deselectAll(): void {
+    if (this.scripts.length === 0) {
+      return;
+    }
+    const selectedScriptIds = this.scripts.getItems().map((script) => script.id);
+    this.processChanges({
+      changes: selectedScriptIds.map((scriptId): ScriptSelectionChange => ({
+        scriptId,
+        newStatus: {
+          isSelected: false,
+        },
+      })),
+    });
+  }
+
+  public selectOnly(scripts: readonly IScript[]): void {
+    if (scripts.length === 0) {
+      throw new Error('Provided script array is empty. To deselect all scripts, please use the deselectAll() method instead.');
+    }
+    this.processChanges({
+      changes: [
+        ...getScriptIdsToBeDeselected(this.scripts, scripts)
+          .map((scriptId): ScriptSelectionChange => ({
+            scriptId,
+            newStatus: {
+              isSelected: false,
+            },
+          })),
+        ...getScriptIdsToBeSelected(this.scripts, scripts)
+          .map((scriptId): ScriptSelectionChange => ({
+            scriptId,
+            newStatus: {
+              isSelected: true,
+              isReverted: false,
+            },
+          })),
+      ],
+    });
+  }
+
+  private processScriptChanges(changes: readonly ScriptSelectionChange[]): void {
+    let totalChanged = 0;
+    for (const change of changes) {
+      totalChanged += this.applyChange(change);
+    }
+    if (totalChanged > 0) {
+      this.changed.notify(this.scripts.getItems());
+    }
+  }
+
+  private applyChange(change: ScriptSelectionChange): number {
+    const script = this.collection.getScript(change.scriptId);
+    if (change.newStatus.isSelected) {
+      return this.addOrUpdateScript(script.id, change.newStatus.isReverted);
+    }
+    return this.removeScript(script.id);
+  }
+
+  private addOrUpdateScript(scriptId: string, revert: boolean): number {
+    const script = this.collection.getScript(scriptId);
+    const selectedScript = new UserSelectedScript(script, revert);
+    if (!this.scripts.exists(selectedScript.id)) {
+      this.scripts.addItem(selectedScript);
+      return 1;
+    }
+    const existingSelectedScript = this.scripts.getById(selectedScript.id);
+    if (equals(selectedScript, existingSelectedScript)) {
+      return 0;
+    }
+    this.scripts.addOrUpdateItem(selectedScript);
+    return 1;
+  }
+
+  private removeScript(scriptId: string): number {
+    if (!this.scripts.exists(scriptId)) {
+      return 0;
+    }
+    this.scripts.removeItem(scriptId);
+    return 1;
+  }
+}
+
+function getScriptIdsToBeSelected(
+  existingItems: ReadonlyRepository<string, SelectedScript>,
+  desiredScripts: readonly IScript[],
+): string[] {
+  return desiredScripts
+    .filter((script) => !existingItems.exists(script.id))
+    .map((script) => script.id);
+}
+
+function getScriptIdsToBeDeselected(
+  existingItems: ReadonlyRepository<string, SelectedScript>,
+  desiredScripts: readonly IScript[],
+): string[] {
+  return existingItems
+    .getItems()
+    .filter((existing) => !desiredScripts.some((script) => existing.id === script.id))
+    .map((script) => script.id);
+}
+
+function equals(a: SelectedScript, b: SelectedScript): boolean {
+  return a.script.equals(b.script.id) && a.revert === b.revert;
+}
diff --git a/src/application/Context/State/Selection/Script/ScriptSelection.ts b/src/application/Context/State/Selection/Script/ScriptSelection.ts
new file mode 100644
index 00000000..f3d202b4
--- /dev/null
+++ b/src/application/Context/State/Selection/Script/ScriptSelection.ts
@@ -0,0 +1,17 @@
+import { IEventSource } from '@/infrastructure/Events/IEventSource';
+import { IScript } from '@/domain/IScript';
+import { SelectedScript } from './SelectedScript';
+import { ScriptSelectionChangeCommand } from './ScriptSelectionChange';
+
+export interface ReadonlyScriptSelection {
+  readonly changed: IEventSource<readonly SelectedScript[]>;
+  readonly selectedScripts: readonly SelectedScript[];
+  isSelected(scriptId: string): boolean;
+}
+
+export interface ScriptSelection extends ReadonlyScriptSelection {
+  selectOnly(scripts: readonly IScript[]): void;
+  selectAll(): void;
+  deselectAll(): void;
+  processChanges(action: ScriptSelectionChangeCommand): void;
+}
diff --git a/src/application/Context/State/Selection/Script/ScriptSelectionChange.ts b/src/application/Context/State/Selection/Script/ScriptSelectionChange.ts
new file mode 100644
index 00000000..bc596d02
--- /dev/null
+++ b/src/application/Context/State/Selection/Script/ScriptSelectionChange.ts
@@ -0,0 +1,15 @@
+export type ScriptSelectionStatus = {
+  readonly isSelected: true;
+  readonly isReverted: boolean;
+} | {
+  readonly isSelected: false;
+};
+
+export interface ScriptSelectionChange {
+  readonly scriptId: string;
+  readonly newStatus: ScriptSelectionStatus;
+}
+
+export interface ScriptSelectionChangeCommand {
+  readonly changes: ReadonlyArray<ScriptSelectionChange>;
+}
diff --git a/src/application/Context/State/Selection/Script/SelectedScript.ts b/src/application/Context/State/Selection/Script/SelectedScript.ts
new file mode 100644
index 00000000..ef1dd7f8
--- /dev/null
+++ b/src/application/Context/State/Selection/Script/SelectedScript.ts
@@ -0,0 +1,9 @@
+import { IEntity } from '@/infrastructure/Entity/IEntity';
+import { IScript } from '@/domain/IScript';
+
+type ScriptId = IScript['id'];
+
+export interface SelectedScript extends IEntity<ScriptId> {
+  readonly script: IScript;
+  readonly revert: boolean;
+}
diff --git a/src/application/Context/State/Selection/SelectedScript.ts b/src/application/Context/State/Selection/Script/UserSelectedScript.ts
similarity index 50%
rename from src/application/Context/State/Selection/SelectedScript.ts
rename to src/application/Context/State/Selection/Script/UserSelectedScript.ts
index e3966a56..b0d70d4b 100644
--- a/src/application/Context/State/Selection/SelectedScript.ts
+++ b/src/application/Context/State/Selection/Script/UserSelectedScript.ts
@@ -1,14 +1,17 @@
 import { BaseEntity } from '@/infrastructure/Entity/BaseEntity';
 import { IScript } from '@/domain/IScript';
+import { SelectedScript } from './SelectedScript';
 
-export class SelectedScript extends BaseEntity<string> {
+type SelectedScriptId = SelectedScript['id'];
+
+export class UserSelectedScript extends BaseEntity<SelectedScriptId> {
   constructor(
     public readonly script: IScript,
     public readonly revert: boolean,
   ) {
     super(script.id);
     if (revert && !script.canRevert()) {
-      throw new Error('cannot revert an irreversible script');
+      throw new Error(`The script with ID '${script.id}' is not reversible and cannot be reverted.`);
     }
   }
 }
diff --git a/src/application/Context/State/Selection/UserSelection.ts b/src/application/Context/State/Selection/UserSelection.ts
index bba4d93d..c7b01964 100644
--- a/src/application/Context/State/Selection/UserSelection.ts
+++ b/src/application/Context/State/Selection/UserSelection.ts
@@ -1,164 +1,12 @@
-import { InMemoryRepository } from '@/infrastructure/Repository/InMemoryRepository';
-import { IScript } from '@/domain/IScript';
-import { EventSource } from '@/infrastructure/Events/EventSource';
-import { IRepository } from '@/infrastructure/Repository/IRepository';
-import { ICategory } from '@/domain/ICategory';
-import { ICategoryCollection } from '@/domain/ICategoryCollection';
-import { IUserSelection } from './IUserSelection';
-import { SelectedScript } from './SelectedScript';
+import { CategorySelection, ReadonlyCategorySelection } from './Category/CategorySelection';
+import { ReadonlyScriptSelection, ScriptSelection } from './Script/ScriptSelection';
 
-export class UserSelection implements IUserSelection {
-  public readonly changed = new EventSource<ReadonlyArray<SelectedScript>>();
-
-  private readonly scripts: IRepository<string, SelectedScript>;
-
-  constructor(
-    private readonly collection: ICategoryCollection,
-    selectedScripts: ReadonlyArray<SelectedScript>,
-  ) {
-    this.scripts = new InMemoryRepository<string, SelectedScript>();
-    for (const script of selectedScripts) {
-      this.scripts.addItem(script);
-    }
-  }
-
-  public areAllSelected(category: ICategory): boolean {
-    if (this.selectedScripts.length === 0) {
-      return false;
-    }
-    const scripts = category.getAllScriptsRecursively();
-    if (this.selectedScripts.length < scripts.length) {
-      return false;
-    }
-    return scripts.every(
-      (script) => this.selectedScripts.some((selected) => selected.id === script.id),
-    );
-  }
-
-  public isAnySelected(category: ICategory): boolean {
-    if (this.selectedScripts.length === 0) {
-      return false;
-    }
-    return this.selectedScripts.some((s) => category.includes(s.script));
-  }
-
-  public removeAllInCategory(categoryId: number): void {
-    const category = this.collection.getCategory(categoryId);
-    const scriptsToRemove = category.getAllScriptsRecursively()
-      .filter((script) => this.scripts.exists(script.id));
-    if (!scriptsToRemove.length) {
-      return;
-    }
-    for (const script of scriptsToRemove) {
-      this.scripts.removeItem(script.id);
-    }
-    this.changed.notify(this.scripts.getItems());
-  }
-
-  public addOrUpdateAllInCategory(categoryId: number, revert = false): void {
-    const scriptsToAddOrUpdate = this.collection
-      .getCategory(categoryId)
-      .getAllScriptsRecursively()
-      .filter(
-        (script) => !this.scripts.exists(script.id)
-          || this.scripts.getById(script.id).revert !== revert,
-      )
-      .map((script) => new SelectedScript(script, revert));
-    if (!scriptsToAddOrUpdate.length) {
-      return;
-    }
-    for (const script of scriptsToAddOrUpdate) {
-      this.scripts.addOrUpdateItem(script);
-    }
-    this.changed.notify(this.scripts.getItems());
-  }
-
-  public addSelectedScript(scriptId: string, revert: boolean): void {
-    const script = this.collection.getScript(scriptId);
-    const selectedScript = new SelectedScript(script, revert);
-    this.scripts.addItem(selectedScript);
-    this.changed.notify(this.scripts.getItems());
-  }
-
-  public addOrUpdateSelectedScript(scriptId: string, revert: boolean): void {
-    const script = this.collection.getScript(scriptId);
-    const selectedScript = new SelectedScript(script, revert);
-    this.scripts.addOrUpdateItem(selectedScript);
-    this.changed.notify(this.scripts.getItems());
-  }
-
-  public removeSelectedScript(scriptId: string): void {
-    this.scripts.removeItem(scriptId);
-    this.changed.notify(this.scripts.getItems());
-  }
-
-  public isSelected(scriptId: string): boolean {
-    return this.scripts.exists(scriptId);
-  }
-
-  /** Get users scripts based on his/her selections */
-  public get selectedScripts(): ReadonlyArray<SelectedScript> {
-    return this.scripts.getItems();
-  }
-
-  public selectAll(): void {
-    const scriptsToSelect = this.collection
-      .getAllScripts()
-      .filter((script) => !this.scripts.exists(script.id))
-      .map((script) => new SelectedScript(script, false));
-    if (scriptsToSelect.length === 0) {
-      return;
-    }
-    for (const script of scriptsToSelect) {
-      this.scripts.addItem(script);
-    }
-    this.changed.notify(this.scripts.getItems());
-  }
-
-  public deselectAll(): void {
-    if (this.scripts.length === 0) {
-      return;
-    }
-    const selectedScriptIds = this.scripts.getItems().map((script) => script.id);
-    for (const scriptId of selectedScriptIds) {
-      this.scripts.removeItem(scriptId);
-    }
-    this.changed.notify([]);
-  }
-
-  public selectOnly(scripts: readonly IScript[]): void {
-    if (!scripts.length) {
-      throw new Error('Scripts are empty. Use deselectAll() if you want to deselect everything');
-    }
-    let totalChanged = 0;
-    totalChanged += this.unselectMissingWithoutNotifying(scripts);
-    totalChanged += this.selectNewWithoutNotifying(scripts);
-    if (totalChanged > 0) {
-      this.changed.notify(this.scripts.getItems());
-    }
-  }
-
-  private unselectMissingWithoutNotifying(scripts: readonly IScript[]): number {
-    if (this.scripts.length === 0 || scripts.length === 0) {
-      return 0;
-    }
-    const existingItems = this.scripts.getItems();
-    const missingIds = existingItems
-      .filter((existing) => !scripts.some((script) => existing.id === script.id))
-      .map((script) => script.id);
-    for (const id of missingIds) {
-      this.scripts.removeItem(id);
-    }
-    return missingIds.length;
-  }
-
-  private selectNewWithoutNotifying(scripts: readonly IScript[]): number {
-    const unselectedScripts = scripts
-      .filter((script) => !this.scripts.exists(script.id))
-      .map((script) => new SelectedScript(script, false));
-    for (const newScript of unselectedScripts) {
-      this.scripts.addItem(newScript);
-    }
-    return unselectedScripts.length;
-  }
+export interface ReadonlyUserSelection {
+  readonly categories: ReadonlyCategorySelection;
+  readonly scripts: ReadonlyScriptSelection;
+}
+
+export interface UserSelection extends ReadonlyUserSelection {
+  readonly categories: CategorySelection;
+  readonly scripts: ScriptSelection;
 }
diff --git a/src/application/Context/State/Selection/UserSelectionFacade.ts b/src/application/Context/State/Selection/UserSelectionFacade.ts
new file mode 100644
index 00000000..ef6cbfdf
--- /dev/null
+++ b/src/application/Context/State/Selection/UserSelectionFacade.ts
@@ -0,0 +1,39 @@
+import { ICategoryCollection } from '@/domain/ICategoryCollection';
+import { CategorySelection } from './Category/CategorySelection';
+import { ScriptToCategorySelectionMapper } from './Category/ScriptToCategorySelectionMapper';
+import { DebouncedScriptSelection } from './Script/DebouncedScriptSelection';
+import { ScriptSelection } from './Script/ScriptSelection';
+import { UserSelection } from './UserSelection';
+import { SelectedScript } from './Script/SelectedScript';
+
+export class UserSelectionFacade implements UserSelection {
+  public readonly categories: CategorySelection;
+
+  public readonly scripts: ScriptSelection;
+
+  constructor(
+    collection: ICategoryCollection,
+    selectedScripts: readonly SelectedScript[],
+    scriptsFactory = DefaultScriptsFactory,
+    categoriesFactory = DefaultCategoriesFactory,
+  ) {
+    this.scripts = scriptsFactory(collection, selectedScripts);
+    this.categories = categoriesFactory(this.scripts, collection);
+  }
+}
+
+export type ScriptsFactory = (
+  ...params: ConstructorParameters<typeof DebouncedScriptSelection>
+) => ScriptSelection;
+
+const DefaultScriptsFactory: ScriptsFactory = (
+  ...params
+) => new DebouncedScriptSelection(...params);
+
+export type CategoriesFactory = (
+  ...params: ConstructorParameters<typeof ScriptToCategorySelectionMapper>
+) => CategorySelection;
+
+const DefaultCategoriesFactory: CategoriesFactory = (
+  ...params
+) => new ScriptToCategorySelectionMapper(...params);
diff --git a/src/application/Repository/Repository.ts b/src/application/Repository/Repository.ts
new file mode 100644
index 00000000..dd364978
--- /dev/null
+++ b/src/application/Repository/Repository.ts
@@ -0,0 +1,17 @@
+import { IEntity } from '@/infrastructure/Entity/IEntity';
+
+export interface ReadonlyRepository<TKey, TEntity extends IEntity<TKey>> {
+  readonly length: number;
+  getItems(predicate?: (entity: TEntity) => boolean): readonly TEntity[];
+  getById(id: TKey): TEntity;
+  exists(id: TKey): boolean;
+}
+
+export interface MutableRepository<TKey, TEntity extends IEntity<TKey>> {
+  addItem(item: TEntity): void;
+  addOrUpdateItem(item: TEntity): void;
+  removeItem(id: TKey): void;
+}
+
+export interface Repository<TKey, TEntity extends IEntity<TKey>>
+  extends ReadonlyRepository<TKey, TEntity>, MutableRepository<TKey, TEntity> { }
diff --git a/src/infrastructure/Repository/IRepository.ts b/src/infrastructure/Repository/IRepository.ts
deleted file mode 100644
index e7c14e0b..00000000
--- a/src/infrastructure/Repository/IRepository.ts
+++ /dev/null
@@ -1,11 +0,0 @@
-import { IEntity } from '../Entity/IEntity';
-
-export interface IRepository<TKey, TEntity extends IEntity<TKey>> {
-  readonly length: number;
-  getItems(predicate?: (entity: TEntity) => boolean): TEntity[];
-  getById(id: TKey): TEntity;
-  addItem(item: TEntity): void;
-  addOrUpdateItem(item: TEntity): void;
-  removeItem(id: TKey): void;
-  exists(id: TKey): boolean;
-}
diff --git a/src/infrastructure/Repository/InMemoryRepository.ts b/src/infrastructure/Repository/InMemoryRepository.ts
index af0da495..597fadb8 100644
--- a/src/infrastructure/Repository/InMemoryRepository.ts
+++ b/src/infrastructure/Repository/InMemoryRepository.ts
@@ -1,8 +1,8 @@
 import { IEntity } from '../Entity/IEntity';
-import { IRepository } from './IRepository';
+import { Repository } from '../../application/Repository/Repository';
 
 export class InMemoryRepository<TKey, TEntity extends IEntity<TKey>>
-implements IRepository<TKey, TEntity> {
+implements Repository<TKey, TEntity> {
   private readonly items: TEntity[];
 
   constructor(items?: TEntity[]) {
diff --git a/src/presentation/components/Code/TheCodeArea.vue b/src/presentation/components/Code/TheCodeArea.vue
index 638b6390..16cc682f 100644
--- a/src/presentation/components/Code/TheCodeArea.vue
+++ b/src/presentation/components/Code/TheCodeArea.vue
@@ -3,8 +3,10 @@
     v-non-collapsing
     @size-changed="sizeChanged()"
   >
+    <!-- `data-test-highlighted-range` is a test hook for assessing highlighted text range -->
     <div
       :id="editorId"
+      :data-test-highlighted-range="highlightedRange"
       class="code-area"
     />
   </SizeObserver>
@@ -12,7 +14,7 @@
 
 <script lang="ts">
 import {
-  defineComponent, onUnmounted, onMounted,
+  defineComponent, onUnmounted, onMounted, ref,
 } from 'vue';
 import { injectKey } from '@/presentation/injectionSymbols';
 import { ICodeChangedEvent } from '@/application/Context/State/Code/Event/ICodeChangedEvent';
@@ -42,6 +44,8 @@ export default defineComponent({
     const { events } = injectKey((keys) => keys.useAutoUnsubscribedEvents);
 
     const editorId = 'codeEditor';
+    const highlightedRange = ref(0);
+
     let editor: ace.Ace.Editor | undefined;
     let currentMarkerId: number | undefined;
 
@@ -99,6 +103,7 @@ export default defineComponent({
       }
       editor?.session.removeMarker(currentMarkerId);
       currentMarkerId = undefined;
+      highlightedRange.value = 0;
     }
 
     function reactToChanges(event: ICodeChangedEvent, scripts: ReadonlyArray<IScript>) {
@@ -121,6 +126,7 @@ export default defineComponent({
         'code-area__highlight',
         'fullLine',
       );
+      highlightedRange.value = endRow - startRow;
     }
 
     function scrollToLine(row: number) {
@@ -133,6 +139,7 @@ export default defineComponent({
 
     return {
       editorId,
+      highlightedRange,
       sizeChanged,
     };
   },
diff --git a/src/presentation/components/Scripts/Menu/Selector/SelectionTypeHandler.ts b/src/presentation/components/Scripts/Menu/Selector/SelectionTypeHandler.ts
index 46137907..dc97f6a5 100644
--- a/src/presentation/components/Scripts/Menu/Selector/SelectionTypeHandler.ts
+++ b/src/presentation/components/Scripts/Menu/Selector/SelectionTypeHandler.ts
@@ -1,9 +1,9 @@
 import { IScript } from '@/domain/IScript';
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
 import { RecommendationLevel } from '@/domain/RecommendationLevel';
 import { scrambledEqual } from '@/application/Common/Array';
-import { IReadOnlyUserSelection, IUserSelection } from '@/application/Context/State/Selection/IUserSelection';
 import { ICategoryCollection } from '@/domain/ICategoryCollection';
+import { ReadonlyScriptSelection, ScriptSelection } from '@/application/Context/State/Selection/Script/ScriptSelection';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
 
 export enum SelectionType {
   Standard,
@@ -34,12 +34,12 @@ export function getCurrentSelectionType(context: SelectionCheckContext): Selecti
 }
 
 export interface SelectionCheckContext {
-  readonly selection: IReadOnlyUserSelection;
+  readonly selection: ReadonlyScriptSelection;
   readonly collection: ICategoryCollection;
 }
 
 export interface SelectionMutationContext {
-  readonly selection: IUserSelection,
+  readonly selection: ScriptSelection,
   readonly collection: ICategoryCollection,
 }
 
diff --git a/src/presentation/components/Scripts/Menu/Selector/TheSelector.vue b/src/presentation/components/Scripts/Menu/Selector/TheSelector.vue
index 7aa62287..051ae56c 100644
--- a/src/presentation/components/Scripts/Menu/Selector/TheSelector.vue
+++ b/src/presentation/components/Scripts/Menu/Selector/TheSelector.vue
@@ -91,7 +91,7 @@ export default defineComponent({
 
     const currentSelectionType = computed<SelectionType>({
       get: () => getCurrentSelectionType({
-        selection: currentSelection.value,
+        selection: currentSelection.value.scripts,
         collection: currentCollection.value,
       }),
       set: (type: SelectionType) => {
@@ -105,7 +105,7 @@ export default defineComponent({
       }
       modifyCurrentSelection((mutableSelection) => {
         setCurrentSelectionType(type, {
-          selection: mutableSelection,
+          selection: mutableSelection.scripts,
           collection: currentCollection.value,
         });
       });
diff --git a/src/presentation/components/Scripts/View/Cards/CardSelectionIndicator.vue b/src/presentation/components/Scripts/View/Cards/CardSelectionIndicator.vue
index eb4e3914..42b1493e 100644
--- a/src/presentation/components/Scripts/View/Cards/CardSelectionIndicator.vue
+++ b/src/presentation/components/Scripts/View/Cards/CardSelectionIndicator.vue
@@ -38,11 +38,11 @@ export default defineComponent({
     );
 
     const isAnyChildSelected = computed<boolean>(
-      () => currentSelection.value.isAnySelected(currentCategory.value),
+      () => currentSelection.value.categories.isAnyScriptSelected(currentCategory.value),
     );
 
     const areAllChildrenSelected = computed<boolean>(
-      () => currentSelection.value.areAllSelected(currentCategory.value),
+      () => currentSelection.value.categories.areAllScriptsSelected(currentCategory.value),
     );
 
     return {
diff --git a/src/presentation/components/Scripts/View/Tree/NodeContent/RevertToggle.vue b/src/presentation/components/Scripts/View/Tree/NodeContent/RevertToggle.vue
index 807bb470..aa3582ce 100644
--- a/src/presentation/components/Scripts/View/Tree/NodeContent/RevertToggle.vue
+++ b/src/presentation/components/Scripts/View/Tree/NodeContent/RevertToggle.vue
@@ -41,7 +41,7 @@ export default defineComponent({
 
     const isReverted = computed<boolean>({
       get() {
-        const { selectedScripts } = currentSelection.value;
+        const { selectedScripts } = currentSelection.value.scripts;
         return revertHandler.value.getState(selectedScripts);
       },
       set: (value: boolean) => {
diff --git a/src/presentation/components/Scripts/View/Tree/NodeContent/Reverter/CategoryReverter.ts b/src/presentation/components/Scripts/View/Tree/NodeContent/Reverter/CategoryReverter.ts
index 6e0229fc..1c92826b 100644
--- a/src/presentation/components/Scripts/View/Tree/NodeContent/Reverter/CategoryReverter.ts
+++ b/src/presentation/components/Scripts/View/Tree/NodeContent/Reverter/CategoryReverter.ts
@@ -1,6 +1,6 @@
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
-import { IUserSelection } from '@/application/Context/State/Selection/IUserSelection';
+import { UserSelection } from '@/application/Context/State/Selection/UserSelection';
 import { ICategoryCollection } from '@/domain/ICategoryCollection';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
 import { getCategoryId } from '../../TreeViewAdapter/CategoryNodeMetadataConverter';
 import { IReverter } from './IReverter';
 import { ScriptReverter } from './ScriptReverter';
@@ -19,8 +19,16 @@ export class CategoryReverter implements IReverter {
     return this.scriptReverters.every((script) => script.getState(selectedScripts));
   }
 
-  public selectWithRevertState(newState: boolean, selection: IUserSelection): void {
-    selection.addOrUpdateAllInCategory(this.categoryId, newState);
+  public selectWithRevertState(newState: boolean, selection: UserSelection): void {
+    selection.categories.processChanges({
+      changes: [{
+        categoryId: this.categoryId,
+        newStatus: {
+          isSelected: true,
+          isReverted: newState,
+        },
+      }],
+    });
   }
 }
 
diff --git a/src/presentation/components/Scripts/View/Tree/NodeContent/Reverter/IReverter.ts b/src/presentation/components/Scripts/View/Tree/NodeContent/Reverter/IReverter.ts
index 11b70273..cea86c80 100644
--- a/src/presentation/components/Scripts/View/Tree/NodeContent/Reverter/IReverter.ts
+++ b/src/presentation/components/Scripts/View/Tree/NodeContent/Reverter/IReverter.ts
@@ -1,7 +1,7 @@
-import { IUserSelection } from '@/application/Context/State/Selection/IUserSelection';
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
+import { UserSelection } from '@/application/Context/State/Selection/UserSelection';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
 
 export interface IReverter {
   getState(selectedScripts: ReadonlyArray<SelectedScript>): boolean;
-  selectWithRevertState(newState: boolean, selection: IUserSelection): void;
+  selectWithRevertState(newState: boolean, selection: UserSelection): void;
 }
diff --git a/src/presentation/components/Scripts/View/Tree/NodeContent/Reverter/ScriptReverter.ts b/src/presentation/components/Scripts/View/Tree/NodeContent/Reverter/ScriptReverter.ts
index 919863e1..95ea7c2a 100644
--- a/src/presentation/components/Scripts/View/Tree/NodeContent/Reverter/ScriptReverter.ts
+++ b/src/presentation/components/Scripts/View/Tree/NodeContent/Reverter/ScriptReverter.ts
@@ -1,5 +1,5 @@
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
-import { IUserSelection } from '@/application/Context/State/Selection/IUserSelection';
+import { UserSelection } from '@/application/Context/State/Selection/UserSelection';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
 import { getScriptId } from '../../TreeViewAdapter/CategoryNodeMetadataConverter';
 import { IReverter } from './IReverter';
 
@@ -18,7 +18,15 @@ export class ScriptReverter implements IReverter {
     return selectedScript.revert;
   }
 
-  public selectWithRevertState(newState: boolean, selection: IUserSelection): void {
-    selection.addOrUpdateSelectedScript(this.scriptId, newState);
+  public selectWithRevertState(newState: boolean, selection: UserSelection): void {
+    selection.scripts.processChanges({
+      changes: [{
+        scriptId: this.scriptId,
+        newStatus: {
+          isSelected: true,
+          isReverted: newState,
+        },
+      }],
+    });
   }
 }
diff --git a/src/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseCollectionSelectionStateUpdater.ts b/src/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseCollectionSelectionStateUpdater.ts
index 90241c95..91a7c9eb 100644
--- a/src/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseCollectionSelectionStateUpdater.ts
+++ b/src/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseCollectionSelectionStateUpdater.ts
@@ -16,19 +16,38 @@ export function useCollectionSelectionStateUpdater(
       return;
     }
     if (node.state.current.checkState === TreeNodeCheckState.Checked) {
-      if (currentSelection.value.isSelected(node.id)) {
+      if (currentSelection.value.scripts.isSelected(node.id)) {
         return;
       }
       modifyCurrentSelection((selection) => {
-        selection.addSelectedScript(node.id, false);
+        selection.scripts.processChanges({
+          changes: [
+            {
+              scriptId: node.id,
+              newStatus: {
+                isSelected: true,
+                isReverted: false,
+              },
+            },
+          ],
+        });
       });
     }
     if (node.state.current.checkState === TreeNodeCheckState.Unchecked) {
-      if (!currentSelection.value.isSelected(node.id)) {
+      if (!currentSelection.value.scripts.isSelected(node.id)) {
         return;
       }
       modifyCurrentSelection((selection) => {
-        selection.removeSelectedScript(node.id);
+        selection.scripts.processChanges({
+          changes: [
+            {
+              scriptId: node.id,
+              newStatus: {
+                isSelected: false,
+              },
+            },
+          ],
+        });
       });
     }
   }
diff --git a/src/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseSelectedScriptNodeIds.ts b/src/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseSelectedScriptNodeIds.ts
index 451f19e2..e60ebc49 100644
--- a/src/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseSelectedScriptNodeIds.ts
+++ b/src/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseSelectedScriptNodeIds.ts
@@ -13,6 +13,7 @@ export function useSelectedScriptNodeIds(
   const selectedNodeIds = computed<readonly string[]>(() => {
     return currentSelection
       .value
+      .scripts
       .selectedScripts
       .map((selected) => scriptNodeIdParser(selected.script));
   });
diff --git a/src/presentation/components/Shared/Hooks/UseUserSelectionState.ts b/src/presentation/components/Shared/Hooks/UseUserSelectionState.ts
index 62edb5ed..499467b3 100644
--- a/src/presentation/components/Shared/Hooks/UseUserSelectionState.ts
+++ b/src/presentation/components/Shared/Hooks/UseUserSelectionState.ts
@@ -1,5 +1,5 @@
 import { shallowReadonly, shallowRef, triggerRef } from 'vue';
-import { IReadOnlyUserSelection, IUserSelection } from '@/application/Context/State/Selection/IUserSelection';
+import type { ReadonlyUserSelection, UserSelection } from '@/application/Context/State/Selection/UserSelection';
 import type { useAutoUnsubscribedEvents } from './UseAutoUnsubscribedEvents';
 import type { useCollectionState } from './UseCollectionState';
 
@@ -10,12 +10,12 @@ export function useUserSelectionState(
   const { events } = autoUnsubscribedEvents;
   const { onStateChange, modifyCurrentState, currentState } = collectionState;
 
-  const currentSelection = shallowRef<IReadOnlyUserSelection>(currentState.value.selection);
+  const currentSelection = shallowRef<ReadonlyUserSelection>(currentState.value.selection);
 
   onStateChange((state) => {
     updateSelection(state.selection);
     events.unsubscribeAllAndRegister([
-      state.selection.changed.on(() => {
+      state.selection.scripts.changed.on(() => {
         updateSelection(state.selection);
       }),
     ]);
@@ -27,7 +27,7 @@ export function useUserSelectionState(
     });
   }
 
-  function updateSelection(newSelection: IReadOnlyUserSelection) {
+  function updateSelection(newSelection: ReadonlyUserSelection) {
     if (currentSelection.value === newSelection) {
       // Do not trust Vue tracking, the changed selection object
       // reference may stay same for same collection.
@@ -44,5 +44,5 @@ export function useUserSelectionState(
 }
 
 export type SelectionModifier = (
-  state: IUserSelection,
+  state: UserSelection,
 ) => void;
diff --git a/src/presentation/components/Shared/SizeObserver.vue b/src/presentation/components/Shared/SizeObserver.vue
index 0baeb627..593da74d 100644
--- a/src/presentation/components/Shared/SizeObserver.vue
+++ b/src/presentation/components/Shared/SizeObserver.vue
@@ -9,7 +9,7 @@ import {
   defineComponent, shallowRef, onMounted, onBeforeUnmount, watch,
 } from 'vue';
 import { useResizeObserverPolyfill } from '@/presentation/components/Shared/Hooks/UseResizeObserverPolyfill';
-import { throttle } from '@/presentation/components/Shared/Throttle';
+import { throttle } from '@/application/Common/Timing/Throttle';
 
 export default defineComponent({
   emits: {
diff --git a/tests/e2e/card-list-layout-stability-on-load.cy.ts b/tests/e2e/card-list-layout-stability-on-load.cy.ts
index 8fa114be..fe0f4501 100644
--- a/tests/e2e/card-list-layout-stability-on-load.cy.ts
+++ b/tests/e2e/card-list-layout-stability-on-load.cy.ts
@@ -1,5 +1,5 @@
 // eslint-disable-next-line max-classes-per-file
-import { waitForHeaderBrandTitle } from './shared/ApplicationLoad';
+import { getHeaderBrandTitle } from './support/interactions/header';
 
 interface Stoppable {
   stop(): void;
@@ -175,7 +175,7 @@ enum ApplicationLoadStep {
 const checkpoints: Record<ApplicationLoadStep, () => void> = {
   [ApplicationLoadStep.IndexHtmlLoaded]: () => cy.get('#app').should('be.visible'),
   [ApplicationLoadStep.AppVueLoaded]: () => cy.get('.app__wrapper').should('be.visible'),
-  [ApplicationLoadStep.HeaderBrandTitleLoaded]: () => waitForHeaderBrandTitle(),
+  [ApplicationLoadStep.HeaderBrandTitleLoaded]: () => getHeaderBrandTitle(),
 };
 
 class ContinuousRunner implements Stoppable {
diff --git a/tests/e2e/code-highlighting.cy.ts b/tests/e2e/code-highlighting.cy.ts
new file mode 100644
index 00000000..9a9b82ff
--- /dev/null
+++ b/tests/e2e/code-highlighting.cy.ts
@@ -0,0 +1,47 @@
+import { expectExists } from '@tests/shared/Assertions/ExpectExists';
+import { openCard } from './support/interactions/card';
+
+describe('script selection highlighting', () => {
+  it('highlights more when multiple scripts are selected', () => {
+    // Regression test for a bug where selecting multiple scripts only highlighted the last one.
+    cy.visit('/');
+    selectLastScript();
+    getCurrentHighlightRange((lastScriptHighlightRange) => {
+      cy.log(`Highlight height for last script: ${lastScriptHighlightRange}`);
+      cy.visit('/');
+      selectAllScripts();
+      getCurrentHighlightRange((allScriptsHighlightRange) => {
+        cy.log(`Highlight height for all scripts: ${allScriptsHighlightRange}`);
+        expect(allScriptsHighlightRange).to.be.greaterThan(lastScriptHighlightRange);
+      });
+    });
+  });
+});
+
+function selectLastScript() {
+  openCard({
+    cardIndex: -1, // last card
+  });
+  cy.get('.node')
+    .last()
+    .click({ force: true });
+}
+
+function selectAllScripts() {
+  cy.contains('span', 'All')
+    .click();
+}
+
+function getCurrentHighlightRange(
+  callback: (highlightedRange: number) => void,
+) {
+  cy
+    .get('#codeEditor')
+    .invoke('attr', 'data-test-highlighted-range')
+    .should('not.be.empty')
+    .and('not.equal', '0')
+    .then((range) => {
+      expectExists(range);
+      callback(parseInt(range, 10));
+    });
+}
diff --git a/tests/e2e/initialization.cy.ts b/tests/e2e/initialization.cy.ts
index 1826ef7f..89c8f206 100644
--- a/tests/e2e/initialization.cy.ts
+++ b/tests/e2e/initialization.cy.ts
@@ -1,11 +1,11 @@
-import { waitForHeaderBrandTitle } from './shared/ApplicationLoad';
+import { getHeaderBrandTitle } from './support/interactions/header';
 
 describe('application is initialized as expected', () => {
   it('loads title as expected', () => {
     // act
     cy.visit('/');
     // assert
-    waitForHeaderBrandTitle();
+    getHeaderBrandTitle();
   });
   it('there are no console.error output', () => {
     // act
diff --git a/tests/e2e/revert-toggle.cy.ts b/tests/e2e/revert-toggle.cy.ts
index ddb45244..1ea610a3 100644
--- a/tests/e2e/revert-toggle.cy.ts
+++ b/tests/e2e/revert-toggle.cy.ts
@@ -1,12 +1,13 @@
 import { expectExists } from '@tests/shared/Assertions/ExpectExists';
+import { openCard } from './support/interactions/card';
 
 describe('revert toggle', () => {
   context('toggle switch', () => {
     beforeEach(() => {
       cy.visit('/');
-      cy.get('.card')
-        .eq(1) // to get 2nd element, first is often cleanup that may lack revert button
-        .click(); // open the card card
+      openCard({
+        cardIndex: 1, // first is often cleanup that may lack revert button
+      });
       cy.get('.toggle-switch')
         .first()
         .as('toggleSwitch');
diff --git a/tests/e2e/shared/ApplicationLoad.ts b/tests/e2e/shared/ApplicationLoad.ts
deleted file mode 100644
index d9cc3210..00000000
--- a/tests/e2e/shared/ApplicationLoad.ts
+++ /dev/null
@@ -1,3 +0,0 @@
-export function waitForHeaderBrandTitle() {
-  cy.contains('h1', 'privacy.sexy');
-}
diff --git a/tests/e2e/support/interactions/card.ts b/tests/e2e/support/interactions/card.ts
new file mode 100644
index 00000000..5894e7e4
--- /dev/null
+++ b/tests/e2e/support/interactions/card.ts
@@ -0,0 +1,7 @@
+export function openCard(options: {
+  readonly cardIndex: number;
+}) {
+  cy.get('.card')
+    .eq(options.cardIndex)
+    .click();
+}
diff --git a/tests/e2e/support/interactions/header.ts b/tests/e2e/support/interactions/header.ts
new file mode 100644
index 00000000..cd7cb084
--- /dev/null
+++ b/tests/e2e/support/interactions/header.ts
@@ -0,0 +1,3 @@
+export function getHeaderBrandTitle() {
+  cy.contains('h1', 'privacy.sexy');
+}
diff --git a/tests/unit/application/Common/Timing/BatchedDebounce.spec.ts b/tests/unit/application/Common/Timing/BatchedDebounce.spec.ts
new file mode 100644
index 00000000..12eace1d
--- /dev/null
+++ b/tests/unit/application/Common/Timing/BatchedDebounce.spec.ts
@@ -0,0 +1,144 @@
+import { describe, it, expect } from 'vitest';
+import { batchedDebounce } from '@/application/Common/Timing/BatchedDebounce';
+import { TimerStub } from '@tests/unit/shared/Stubs/TimerStub';
+
+describe('batchedDebounce', () => {
+  describe('immediate invocation', () => {
+    it('does not call the the callback immediately on the first call', () => {
+      // arrange
+      const { calledBatches, callback } = createObservableCallback();
+      const callArg = 'first';
+      const debounceFunc = batchedDebounce(callback, 100, new TimerStub());
+
+      // act
+      debounceFunc(callArg);
+
+      // assert
+      expect(calledBatches).to.have.lengthOf(0);
+    });
+  });
+
+  describe('debounce timing', () => {
+    it('executes the callback after the debounce period', () => {
+      // arrange
+      const { calledBatches, callback } = createObservableCallback();
+      const expectedArg = 'first';
+      const debouncePeriodInMs = 100;
+      const timer = new TimerStub();
+      const debounceFunc = batchedDebounce(callback, debouncePeriodInMs, timer);
+
+      // act
+      debounceFunc(expectedArg);
+      timer.tickNext(debouncePeriodInMs);
+
+      // assert
+      expect(calledBatches).to.have.lengthOf(1);
+      expect(calledBatches).to.deep.include([expectedArg]);
+    });
+    it('prevents callback invocation within the debounce period', () => {
+      // arrange
+      const { calledBatches, callback } = createObservableCallback();
+      const debouncePeriodInMs = 100;
+      const timer = new TimerStub();
+      const debounceFunc = batchedDebounce(callback, debouncePeriodInMs, timer);
+
+      // act
+      debounceFunc('first');
+      timer.tickNext(debouncePeriodInMs / 4);
+      debounceFunc('second');
+      timer.tickNext(debouncePeriodInMs / 4);
+      debounceFunc('third');
+      timer.tickNext(debouncePeriodInMs / 4);
+
+      // assert
+      expect(calledBatches).to.have.lengthOf(0);
+    });
+    it('resets debounce timer on subsequent calls', () => {
+      // arrange
+      const timer = new TimerStub();
+      const { calledBatches, callback } = createObservableCallback();
+      const debouncePeriodInMs = 100;
+      const debounceFunc = batchedDebounce(callback, debouncePeriodInMs, timer);
+
+      // act
+      debounceFunc('first');
+      timer.tickNext(debouncePeriodInMs * 0.9);
+      debounceFunc('second');
+      timer.tickNext(debouncePeriodInMs * 0.9);
+      debounceFunc('third');
+      timer.tickNext(debouncePeriodInMs * 0.9);
+
+      // assert
+      expect(calledBatches).to.have.lengthOf(0);
+    });
+    it('does not call the callback again if no new calls are made after the debounce period', () => {
+      // arrange
+      const { calledBatches, callback } = createObservableCallback();
+      const debouncePeriodInMs = 100;
+      const timer = new TimerStub();
+      const debounceFunc = batchedDebounce(callback, debouncePeriodInMs, timer);
+
+      // act
+      debounceFunc('first');
+      timer.tickNext(debouncePeriodInMs);
+      timer.tickNext(debouncePeriodInMs);
+      timer.tickNext(debouncePeriodInMs);
+      timer.tickNext(debouncePeriodInMs);
+
+      // assert
+      expect(calledBatches).to.have.lengthOf(1);
+    });
+  });
+
+  describe('batching calls', () => {
+    it('batches multiple calls within the debounce period', () => {
+      // arrange
+      const { calledBatches, callback } = createObservableCallback();
+      const firstCallArg = 'first';
+      const secondCallArg = 'second';
+      const debouncePeriodInMs = 100;
+      const timer = new TimerStub();
+      const debounceFunc = batchedDebounce(callback, debouncePeriodInMs, timer);
+
+      // act
+      debounceFunc(firstCallArg);
+      debounceFunc(secondCallArg);
+      timer.tickNext(debouncePeriodInMs);
+
+      // assert
+      expect(calledBatches).to.have.lengthOf(1);
+      expect(calledBatches).to.deep.include([firstCallArg, secondCallArg]);
+    });
+    it('handles multiple separate batches correctly', () => {
+      // arrange
+      const { calledBatches, callback } = createObservableCallback();
+      const debouncePeriodInMs = 100;
+      const firstBatchArg = 'first';
+      const secondBatchArg = 'second';
+      const timer = new TimerStub();
+      const debounceFunc = batchedDebounce(callback, debouncePeriodInMs, timer);
+
+      // act
+      debounceFunc(firstBatchArg);
+      timer.tickNext(debouncePeriodInMs);
+      debounceFunc(secondBatchArg);
+      timer.tickNext(debouncePeriodInMs);
+
+      // assert
+      expect(calledBatches).to.have.lengthOf(2);
+      expect(calledBatches[0]).to.deep.equal([firstBatchArg]);
+      expect(calledBatches[1]).to.deep.equal([secondBatchArg]);
+    });
+  });
+});
+
+function createObservableCallback() {
+  const calledBatches = new Array<readonly string[]>();
+  const callback = (batches: readonly string[]): void => {
+    calledBatches.push(batches);
+  };
+  return {
+    calledBatches,
+    callback,
+  };
+}
diff --git a/tests/unit/application/Common/Timing/PlatformTimer.spec.ts b/tests/unit/application/Common/Timing/PlatformTimer.spec.ts
new file mode 100644
index 00000000..61e80c13
--- /dev/null
+++ b/tests/unit/application/Common/Timing/PlatformTimer.spec.ts
@@ -0,0 +1,78 @@
+import {
+  describe, it, expect, beforeEach,
+  afterEach,
+} from 'vitest';
+import { PlatformTimer } from '@/application/Common/Timing/PlatformTimer';
+
+describe('PlatformTimer', () => {
+  let originalSetTimeout: typeof global.setTimeout;
+  let originalClearTimeout: typeof global.clearTimeout;
+  let originalDateNow: typeof global.Date.now;
+
+  beforeEach(() => {
+    originalSetTimeout = global.setTimeout;
+    originalClearTimeout = global.clearTimeout;
+    originalDateNow = Date.now;
+    Date.now = () => originalDateNow();
+  });
+
+  afterEach(() => {
+    global.setTimeout = originalSetTimeout;
+    global.clearTimeout = originalClearTimeout;
+    Date.now = originalDateNow;
+  });
+
+  describe('setTimeout', () => {
+    it('calls the global setTimeout with the provided delay', () => {
+      // arrange
+      const expectedDelay = 55;
+      let actualDelay: number | undefined;
+      global.setTimeout = ((_, delay) => {
+        actualDelay = delay;
+      }) as typeof global.setTimeout;
+      // act
+      PlatformTimer.setTimeout(() => { /* NOOP */ }, expectedDelay);
+      // assert
+      expect(actualDelay).to.equal(expectedDelay);
+    });
+    it('calls the global setTimeout with the provided callback', () => {
+      // arrange
+      const expectedCallback = () => { /* NOOP */ };
+      let actualCallback: typeof expectedCallback | undefined;
+      global.setTimeout = ((callback) => {
+        actualCallback = callback;
+      }) as typeof global.setTimeout;
+      // act
+      PlatformTimer.setTimeout(expectedCallback, 33);
+      // assert
+      expect(actualCallback).to.equal(expectedCallback);
+    });
+  });
+
+  describe('clearTimeout', () => {
+    it('should clear timeout', () => {
+      // arrange
+      let actualTimer: ReturnType<typeof PlatformTimer.setTimeout> | undefined;
+      global.clearTimeout = ((timer) => {
+        actualTimer = timer;
+      }) as typeof global.clearTimeout;
+      const expectedTimer = PlatformTimer.setTimeout(() => { /* NOOP */ }, 1);
+      // act
+      PlatformTimer.clearTimeout(expectedTimer);
+      // assert
+      expect(actualTimer).to.equal(expectedTimer);
+    });
+  });
+
+  describe('dateNow', () => {
+    it('should get current date', () => {
+      // arrange
+      const expected = Date.now();
+      Date.now = () => expected;
+      // act
+      const actual = PlatformTimer.dateNow();
+      // assert
+      expect(expected).to.equal(actual);
+    });
+  });
+});
diff --git a/tests/unit/presentation/components/Shared/Throttle.spec.ts b/tests/unit/application/Common/Timing/Throttle.spec.ts
similarity index 68%
rename from tests/unit/presentation/components/Shared/Throttle.spec.ts
rename to tests/unit/application/Common/Timing/Throttle.spec.ts
index 4af7085f..ecd72372 100644
--- a/tests/unit/presentation/components/Shared/Throttle.spec.ts
+++ b/tests/unit/application/Common/Timing/Throttle.spec.ts
@@ -1,8 +1,6 @@
 import { describe, it, expect } from 'vitest';
-import { throttle, ITimer, Timeout } from '@/presentation/components/Shared/Throttle';
-import { EventSource } from '@/infrastructure/Events/EventSource';
-import { IEventSubscription } from '@/infrastructure/Events/IEventSource';
-import { createMockTimeout } from '@tests/unit/shared/Stubs/TimeoutStub';
+import { TimerStub } from '@tests/unit/shared/Stubs/TimerStub';
+import { throttle } from '@/application/Common/Timing/Throttle';
 
 describe('throttle', () => {
   describe('validates parameters', () => {
@@ -34,7 +32,7 @@ describe('throttle', () => {
   });
   it('should call the callback immediately', () => {
     // arrange
-    const timer = new TimerMock();
+    const timer = new TimerStub();
     let totalRuns = 0;
     const callback = () => totalRuns++;
     const throttleFunc = throttle(callback, 500, timer);
@@ -45,7 +43,7 @@ describe('throttle', () => {
   });
   it('should call the callback again after the timeout', () => {
     // arrange
-    const timer = new TimerMock();
+    const timer = new TimerStub();
     let totalRuns = 0;
     const callback = () => totalRuns++;
     const waitInMs = 500;
@@ -60,7 +58,7 @@ describe('throttle', () => {
   });
   it('should call the callback at most once at given time', () => {
     // arrange
-    const timer = new TimerMock();
+    const timer = new TimerStub();
     let totalRuns = 0;
     const callback = () => totalRuns++;
     const waitInMs = 500;
@@ -77,7 +75,7 @@ describe('throttle', () => {
   });
   it('should call the callback as long as delay is waited', () => {
     // arrange
-    const timer = new TimerMock();
+    const timer = new TimerStub();
     let totalRuns = 0;
     const callback = () => totalRuns++;
     const waitInMs = 500;
@@ -93,7 +91,7 @@ describe('throttle', () => {
   });
   it('should call arguments as expected', () => {
     // arrange
-    const timer = new TimerMock();
+    const timer = new TimerStub();
     const expected = [1, 2, 3];
     const actual = new Array<number>();
     const callback = (arg: number) => { actual.push(arg); };
@@ -108,41 +106,3 @@ describe('throttle', () => {
     expect(expected).to.deep.equal(actual);
   });
 });
-
-class TimerMock implements ITimer {
-  private timeChanged = new EventSource<number>();
-
-  private subscriptions = new Array<IEventSubscription>();
-
-  private currentTime = 0;
-
-  public setTimeout(callback: () => void, ms: number): Timeout {
-    const runTime = this.currentTime + ms;
-    const subscription = this.timeChanged.on((time) => {
-      if (time >= runTime) {
-        callback();
-        subscription.unsubscribe();
-      }
-    });
-    this.subscriptions.push(subscription);
-    const id = this.subscriptions.length - 1;
-    return createMockTimeout(id);
-  }
-
-  public clearTimeout(timeoutId: Timeout): void {
-    this.subscriptions[+timeoutId].unsubscribe();
-  }
-
-  public dateNow(): number {
-    return this.currentTime;
-  }
-
-  public tickNext(ms: number): void {
-    this.setCurrentTime(this.currentTime + ms);
-  }
-
-  public setCurrentTime(ms: number): void {
-    this.currentTime = ms;
-    this.timeChanged.notify(this.currentTime);
-  }
-}
diff --git a/tests/unit/application/Context/State/CategoryCollectionState.spec.ts b/tests/unit/application/Context/State/CategoryCollectionState.spec.ts
index c505e659..45b05424 100644
--- a/tests/unit/application/Context/State/CategoryCollectionState.spec.ts
+++ b/tests/unit/application/Context/State/CategoryCollectionState.spec.ts
@@ -1,106 +1,167 @@
 import { describe, it, expect } from 'vitest';
-import { UserSelection } from '@/application/Context/State/Selection/UserSelection';
-import { ApplicationCode } from '@/application/Context/State/Code/ApplicationCode';
+import { UserSelectionStub } from '@tests/unit/shared/Stubs/UserSelectionStub';
 import { CategoryCollectionState } from '@/application/Context/State/CategoryCollectionState';
 import { OperatingSystem } from '@/domain/OperatingSystem';
-import { IScript } from '@/domain/IScript';
-import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
-import { CategoryStub } from '@tests/unit/shared/Stubs/CategoryStub';
 import { CategoryCollectionStub } from '@tests/unit/shared/Stubs/CategoryCollectionStub';
+import { ScriptingDefinitionStub } from '@tests/unit/shared/Stubs/ScriptingDefinitionStub';
+import { ICategoryCollection } from '@/domain/ICategoryCollection';
+import { ApplicationCodeStub } from '@tests/unit/shared/Stubs/ApplicationCodeStub';
+import { IScriptingDefinition } from '@/domain/IScriptingDefinition';
+import { expectExists } from '@tests/shared/Assertions/ExpectExists';
+import { ReadonlyScriptSelection } from '@/application/Context/State/Selection/Script/ScriptSelection';
+import { ScriptSelectionStub } from '@tests/unit/shared/Stubs/ScriptSelectionStub';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
+import { UserFilterStub } from '@tests/unit/shared/Stubs/UserFilterStub';
+import type { CodeFactory, FilterFactory, SelectionFactory } from '@/application/Context/State/CategoryCollectionState';
 
 describe('CategoryCollectionState', () => {
   describe('code', () => {
-    it('initialized with empty code', () => {
-      // arrange
-      const collection = new CategoryCollectionStub();
-      const sut = new CategoryCollectionState(collection);
-      // act
-      const code = sut.code.current;
-      // assert
-      expect(!code);
-    });
-    it('reacts to selection changes as expected', () => {
+    it('uses the correct scripting definition', () => {
       // arrange
+      const expectedScripting = new ScriptingDefinitionStub();
       const collection = new CategoryCollectionStub()
-        .withAction(new CategoryStub(0).withScriptIds('scriptId'));
-      const selectionStub = new UserSelection(collection, []);
-      const expectedCodeGenerator = new ApplicationCode(selectionStub, collection.scripting);
-      selectionStub.selectAll();
-      const expectedCode = expectedCodeGenerator.current;
+        .withScripting(expectedScripting);
+      let actualScripting: IScriptingDefinition | undefined;
+      const codeFactoryMock: CodeFactory = (_, scripting) => {
+        actualScripting = scripting;
+        return new ApplicationCodeStub();
+      };
       // act
-      const sut = new CategoryCollectionState(collection);
-      sut.selection.selectAll();
-      const actualCode = sut.code.current;
+      new CategoryCollectionStateBuilder()
+        .withCollection(collection)
+        .withCodeFactory(codeFactoryMock)
+        .build();
       // assert
-      expect(actualCode).to.equal(expectedCode);
+      expectExists(actualScripting);
+      expect(actualScripting).to.equal(expectedScripting);
+    });
+    it('initializes with the expected script selection', () => {
+      // arrange
+      const expectedScriptSelection = new ScriptSelectionStub();
+      const selectionFactoryMock: SelectionFactory = () => {
+        return new UserSelectionStub().withScripts(expectedScriptSelection);
+      };
+      let actualScriptSelection: ReadonlyScriptSelection | undefined;
+      const codeFactoryMock: CodeFactory = (scriptSelection) => {
+        actualScriptSelection = scriptSelection;
+        return new ApplicationCodeStub();
+      };
+      // act
+      new CategoryCollectionStateBuilder()
+        .withCodeFactory(codeFactoryMock)
+        .withSelectionFactory(selectionFactoryMock)
+        .build();
+      // assert
+      expectExists(actualScriptSelection);
+      expect(actualScriptSelection).to.equal(expectedScriptSelection);
     });
   });
   describe('os', () => {
-    it('same as its collection', () => {
+    it('matches the operating system of the collection', () => {
       // arrange
       const expected = OperatingSystem.macOS;
       const collection = new CategoryCollectionStub()
         .withOs(expected);
       // act
-      const sut = new CategoryCollectionState(collection);
+      const sut = new CategoryCollectionStateBuilder()
+        .withCollection(collection)
+        .build();
       // assert
       const actual = sut.os;
       expect(expected).to.equal(actual);
     });
   });
   describe('selection', () => {
-    it('initialized with no selection', () => {
+    it('initializes with empty scripts', () => {
       // arrange
-      const collection = new CategoryCollectionStub();
-      const sut = new CategoryCollectionState(collection);
+      const expectedScripts = [];
+      let actualScripts: readonly SelectedScript[] | undefined;
+      const selectionFactoryMock: SelectionFactory = (_, scripts) => {
+        actualScripts = scripts;
+        return new UserSelectionStub();
+      };
       // act
-      const actual = sut.selection.selectedScripts.length;
+      new CategoryCollectionStateBuilder()
+        .withSelectionFactory(selectionFactoryMock)
+        .build();
       // assert
-      expect(actual).to.equal(0);
+      expectExists(actualScripts);
+      expect(actualScripts).to.deep.equal(expectedScripts);
     });
-    it('can select a script from current collection', () => {
+    it('initializes with the provided collection', () => {
       // arrange
-      const expectedScript = new ScriptStub('scriptId');
-      const collection = new CategoryCollectionStub()
-        .withAction(new CategoryStub(0).withScript(expectedScript));
-      const sut = new CategoryCollectionState(collection);
+      const expectedCollection = new CategoryCollectionStub();
+      let actualCollection: ICategoryCollection | undefined;
+      const selectionFactoryMock: SelectionFactory = (collection) => {
+        actualCollection = collection;
+        return new UserSelectionStub();
+      };
       // act
-      sut.selection.selectAll();
+      new CategoryCollectionStateBuilder()
+        .withCollection(expectedCollection)
+        .withSelectionFactory(selectionFactoryMock)
+        .build();
       // assert
-      expect(sut.selection.selectedScripts.length).to.equal(1);
-      expect(sut.selection.isSelected(expectedScript.id)).to.equal(true);
+      expectExists(actualCollection);
+      expect(actualCollection).to.equal(expectedCollection);
     });
   });
   describe('filter', () => {
-    it('initialized with an empty filter', () => {
+    it('initializes with the provided collection for filtering', () => {
       // arrange
-      const collection = new CategoryCollectionStub();
-      const sut = new CategoryCollectionState(collection);
+      const expectedCollection = new CategoryCollectionStub();
+      let actualCollection: ICategoryCollection | undefined;
+      const filterFactoryMock: FilterFactory = (collection) => {
+        actualCollection = collection;
+        return new UserFilterStub();
+      };
       // act
-      const actual = sut.filter.currentFilter;
+      new CategoryCollectionStateBuilder()
+        .withCollection(expectedCollection)
+        .withFilterFactory(filterFactoryMock)
+        .build();
       // assert
-      expect(actual).to.equal(undefined);
-    });
-    it('can match a script from current collection', () => {
-      // arrange
-      const scriptNameFilter = 'scriptName';
-      const expectedScript = new ScriptStub('scriptId')
-        .withName(scriptNameFilter);
-      const collection = new CategoryCollectionStub()
-        .withAction(new CategoryStub(0).withScript(expectedScript));
-      const sut = new CategoryCollectionState(collection);
-      // act
-      let actualScript: IScript | undefined;
-      sut.filter.filterChanged.on((result) => {
-        result.visit({
-          onApply: (filter) => {
-            [actualScript] = filter.scriptMatches;
-          },
-        });
-      });
-      sut.filter.applyFilter(scriptNameFilter);
-      // assert
-      expect(expectedScript).to.equal(actualScript);
+      expectExists(expectedCollection);
+      expect(expectedCollection).to.equal(actualCollection);
     });
   });
 });
+
+class CategoryCollectionStateBuilder {
+  private collection: ICategoryCollection = new CategoryCollectionStub();
+
+  private codeFactory: CodeFactory = () => new ApplicationCodeStub();
+
+  private selectionFactory: SelectionFactory = () => new UserSelectionStub();
+
+  private filterFactory: FilterFactory = () => new UserFilterStub();
+
+  public withCollection(collection: ICategoryCollection): this {
+    this.collection = collection;
+    return this;
+  }
+
+  public withCodeFactory(codeFactory: CodeFactory): this {
+    this.codeFactory = codeFactory;
+    return this;
+  }
+
+  public withSelectionFactory(selectionFactory: SelectionFactory): this {
+    this.selectionFactory = selectionFactory;
+    return this;
+  }
+
+  public withFilterFactory(filterFactory: FilterFactory): this {
+    this.filterFactory = filterFactory;
+    return this;
+  }
+
+  public build() {
+    return new CategoryCollectionState(
+      this.collection,
+      this.selectionFactory,
+      this.codeFactory,
+      this.filterFactory,
+    );
+  }
+}
diff --git a/tests/unit/application/Context/State/Code/ApplicationCode.spec.ts b/tests/unit/application/Context/State/Code/ApplicationCode.spec.ts
index b1fa20b6..bc69ba34 100644
--- a/tests/unit/application/Context/State/Code/ApplicationCode.spec.ts
+++ b/tests/unit/application/Context/State/Code/ApplicationCode.spec.ts
@@ -1,7 +1,5 @@
 import { describe, it, expect } from 'vitest';
-import { UserSelection } from '@/application/Context/State/Selection/UserSelection';
 import { ApplicationCode } from '@/application/Context/State/Code/ApplicationCode';
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
 import { ICodeChangedEvent } from '@/application/Context/State/Code/Event/ICodeChangedEvent';
 import { IUserScriptGenerator } from '@/application/Context/State/Code/Generation/IUserScriptGenerator';
 import { CodePosition } from '@/application/Context/State/Code/Position/CodePosition';
@@ -9,16 +7,18 @@ import { ICodePosition } from '@/application/Context/State/Code/Position/ICodePo
 import { IScriptingDefinition } from '@/domain/IScriptingDefinition';
 import { IUserScript } from '@/application/Context/State/Code/Generation/IUserScript';
 import { ScriptingDefinitionStub } from '@tests/unit/shared/Stubs/ScriptingDefinitionStub';
-import { CategoryStub } from '@tests/unit/shared/Stubs/CategoryStub';
 import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
-import { CategoryCollectionStub } from '@tests/unit/shared/Stubs/CategoryCollectionStub';
 import { expectExists } from '@tests/shared/Assertions/ExpectExists';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
+import { ScriptSelectionStub } from '@tests/unit/shared/Stubs/ScriptSelectionStub';
 
 describe('ApplicationCode', () => {
   describe('ctor', () => {
     it('empty when selection is empty', () => {
       // arrange
-      const selection = new UserSelection(new CategoryCollectionStub(), []);
+      const selectedScripts = [];
+      const selection = new ScriptSelectionStub()
+        .withSelectedScripts(selectedScripts);
       const definition = new ScriptingDefinitionStub();
       const sut = new ApplicationCode(selection, definition);
       // act
@@ -29,10 +29,9 @@ describe('ApplicationCode', () => {
     it('generates code from script generator when selection is not empty', () => {
       // arrange
       const scripts = [new ScriptStub('first'), new ScriptStub('second')];
-      const collection = new CategoryCollectionStub()
-        .withAction(new CategoryStub(1).withScripts(...scripts));
       const selectedScripts = scripts.map((script) => script.toSelectedScript());
-      const selection = new UserSelection(collection, selectedScripts);
+      const selection = new ScriptSelectionStub()
+        .withSelectedScripts(selectedScripts);
       const definition = new ScriptingDefinitionStub();
       const expected: IUserScript = {
         code: 'expected-code',
@@ -53,10 +52,9 @@ describe('ApplicationCode', () => {
         // arrange
         let signaled: ICodeChangedEvent | undefined;
         const scripts = [new ScriptStub('first'), new ScriptStub('second')];
-        const collection = new CategoryCollectionStub()
-          .withAction(new CategoryStub(1).withScripts(...scripts));
-        const scriptsToSelect = scripts.map((script) => new SelectedScript(script, false));
-        const selection = new UserSelection(collection, scriptsToSelect);
+        const selectedScripts = scripts.map((script) => script.toSelectedScript());
+        const selection = new ScriptSelectionStub()
+          .withSelectedScripts(selectedScripts);
         const definition = new ScriptingDefinitionStub();
         const sut = new ApplicationCode(selection, definition);
         sut.changed.on((code) => {
@@ -73,17 +71,18 @@ describe('ApplicationCode', () => {
         // arrange
         let signaled: ICodeChangedEvent | undefined;
         const scripts = [new ScriptStub('first'), new ScriptStub('second')];
-        const collection = new CategoryCollectionStub()
-          .withAction(new CategoryStub(1).withScripts(...scripts));
-        const scriptsToSelect = scripts.map((script) => new SelectedScript(script, false));
-        const selection = new UserSelection(collection, scriptsToSelect);
+        const selectedScripts = scripts.map(
+          (script) => script.toSelectedScript().withRevert(false),
+        );
+        const selection = new ScriptSelectionStub()
+          .withSelectedScripts(selectedScripts);
         const definition = new ScriptingDefinitionStub();
         const sut = new ApplicationCode(selection, definition);
         sut.changed.on((code) => {
           signaled = code;
         });
         // act
-        selection.changed.notify(scripts.map((s) => new SelectedScript(s, false)));
+        selection.changed.notify(selectedScripts);
         // assert
         expectExists(signaled);
         expect(signaled.code).to.have.length.greaterThan(0);
@@ -94,8 +93,8 @@ describe('ApplicationCode', () => {
       it('sends scripting definition to generator', () => {
         // arrange
         const expectedDefinition = new ScriptingDefinitionStub();
-        const collection = new CategoryCollectionStub();
-        const selection = new UserSelection(collection, []);
+        const selection = new ScriptSelectionStub()
+          .withSelectedScripts([]);
         const generatorMock: IUserScriptGenerator = {
           buildCode: (_, definition) => {
             if (definition !== expectedDefinition) {
@@ -118,13 +117,12 @@ describe('ApplicationCode', () => {
         // arrange
         const expectedDefinition = new ScriptingDefinitionStub();
         const scripts = [new ScriptStub('first'), new ScriptStub('second')];
-        const collection = new CategoryCollectionStub()
-          .withAction(new CategoryStub(1).withScripts(...scripts));
-        const scriptsToSelect = scripts.map((script) => new SelectedScript(script, false));
-        const selection = new UserSelection(collection, scriptsToSelect);
+        const selectedScripts = scripts.map((script) => script.toSelectedScript());
+        const selection = new ScriptSelectionStub()
+          .withSelectedScripts(selectedScripts);
         const generatorMock: IUserScriptGenerator = {
-          buildCode: (selectedScripts) => {
-            if (JSON.stringify(selectedScripts) !== JSON.stringify(scriptsToSelect)) {
+          buildCode: (actualScripts) => {
+            if (JSON.stringify(actualScripts) !== JSON.stringify(selectedScripts)) {
               throw new Error('Unexpected scripts');
             }
             return {
@@ -136,7 +134,7 @@ describe('ApplicationCode', () => {
         // eslint-disable-next-line no-new
         new ApplicationCode(selection, expectedDefinition, generatorMock);
         // act
-        const act = () => selection.changed.notify(scriptsToSelect);
+        const act = () => selection.changed.notify(selectedScripts);
         // assert
         expect(act).to.not.throw();
       });
@@ -144,16 +142,17 @@ describe('ApplicationCode', () => {
         // arrange
         let signaled: ICodeChangedEvent | undefined;
         const scripts = [new ScriptStub('first'), new ScriptStub('second')];
-        const collection = new CategoryCollectionStub()
-          .withAction(new CategoryStub(1).withScripts(...scripts));
-        const scriptsToSelect = scripts.map((script) => new SelectedScript(script, false));
-        const selection = new UserSelection(collection, scriptsToSelect);
+        const selectedScripts = scripts.map(
+          (script) => script.toSelectedScript().withRevert(false),
+        );
+        const selection = new ScriptSelectionStub()
+          .withSelectedScripts(selectedScripts);
         const scriptingDefinition = new ScriptingDefinitionStub();
         const totalLines = 20;
         const expected = new Map<SelectedScript, ICodePosition>(
           [
-            [scriptsToSelect[0], new CodePosition(0, totalLines / 2)],
-            [scriptsToSelect[1], new CodePosition(totalLines / 2, totalLines)],
+            [selectedScripts[0], new CodePosition(0, totalLines / 2)],
+            [selectedScripts[1], new CodePosition(totalLines / 2, totalLines)],
           ],
         );
         const generatorMock: IUserScriptGenerator = {
@@ -169,27 +168,27 @@ describe('ApplicationCode', () => {
           signaled = code;
         });
         // act
-        selection.changed.notify(scriptsToSelect);
+        selection.changed.notify(selectedScripts);
         // assert
         expectExists(signaled);
         expect(signaled.getScriptPositionInCode(scripts[0]))
-          .to.deep.equal(expected.get(scriptsToSelect[0]));
+          .to.deep.equal(expected.get(selectedScripts[0]));
         expect(signaled.getScriptPositionInCode(scripts[1]))
-          .to.deep.equal(expected.get(scriptsToSelect[1]));
+          .to.deep.equal(expected.get(selectedScripts[1]));
       });
     });
   });
 });
 
-interface IScriptGenerationParameters {
-  scripts: readonly SelectedScript[];
-  definition: IScriptingDefinition;
+interface ScriptGenerationParameters {
+  readonly scripts: readonly SelectedScript[];
+  readonly definition: IScriptingDefinition;
 }
 class UserScriptGeneratorMock implements IUserScriptGenerator {
-  private prePlanned = new Map<IScriptGenerationParameters, IUserScript>();
+  private prePlanned = new Map<ScriptGenerationParameters, IUserScript>();
 
   public plan(
-    parameters: IScriptGenerationParameters,
+    parameters: ScriptGenerationParameters,
     result: IUserScript,
   ): UserScriptGeneratorMock {
     this.prePlanned.set(parameters, result);
diff --git a/tests/unit/application/Context/State/Code/Event/CodeChangedEvent.spec.ts b/tests/unit/application/Context/State/Code/Event/CodeChangedEvent.spec.ts
index 3f404ba5..2d63bb95 100644
--- a/tests/unit/application/Context/State/Code/Event/CodeChangedEvent.spec.ts
+++ b/tests/unit/application/Context/State/Code/Event/CodeChangedEvent.spec.ts
@@ -1,10 +1,10 @@
 import { describe, it, expect } from 'vitest';
 import { CodeChangedEvent } from '@/application/Context/State/Code/Event/CodeChangedEvent';
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
 import { ICodePosition } from '@/application/Context/State/Code/Position/ICodePosition';
 import { CodePosition } from '@/application/Context/State/Code/Position/CodePosition';
 import { SelectedScriptStub } from '@tests/unit/shared/Stubs/SelectedScriptStub';
 import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
 
 describe('CodeChangedEvent', () => {
   describe('ctor', () => {
@@ -15,8 +15,8 @@ describe('CodeChangedEvent', () => {
         const nonExistingLine1 = 2;
         const nonExistingLine2 = 31;
         const newScripts = new Map<SelectedScript, ICodePosition>([
-          [new SelectedScriptStub('1'), new CodePosition(0, nonExistingLine1)],
-          [new SelectedScriptStub('2'), new CodePosition(0, nonExistingLine2)],
+          [new SelectedScriptStub(new ScriptStub('1')), new CodePosition(0, nonExistingLine1)],
+          [new SelectedScriptStub(new ScriptStub('2')), new CodePosition(0, nonExistingLine2)],
         ]);
         // act
         let errorText = '';
@@ -47,7 +47,7 @@ describe('CodeChangedEvent', () => {
         for (const testCase of testCases) {
           it(testCase.name, () => {
             const newScripts = new Map<SelectedScript, ICodePosition>([
-              [new SelectedScriptStub('1'), testCase.position],
+              [new SelectedScriptStub(new ScriptStub('1')), testCase.position],
             ]);
             // act
             const act = () => new CodeChangedEventBuilder()
@@ -76,12 +76,15 @@ describe('CodeChangedEvent', () => {
     it('returns new scripts when scripts are added', () => {
       // arrange
       const expected = [new ScriptStub('3'), new ScriptStub('4')];
-      const initialScripts = [new SelectedScriptStub('1'), new SelectedScriptStub('2')];
+      const initialScripts = [
+        new SelectedScriptStub(new ScriptStub('1')),
+        new SelectedScriptStub(new ScriptStub('2')),
+      ];
       const newScripts = new Map<SelectedScript, ICodePosition>([
         [initialScripts[0], new CodePosition(0, 1)],
         [initialScripts[1], new CodePosition(0, 1)],
-        [new SelectedScript(expected[0], false), new CodePosition(0, 1)],
-        [new SelectedScript(expected[1], false), new CodePosition(0, 1)],
+        [new SelectedScriptStub(expected[0]).withRevert(false), new CodePosition(0, 1)],
+        [new SelectedScriptStub(expected[1]).withRevert(false), new CodePosition(0, 1)],
       ]);
       const sut = new CodeChangedEventBuilder()
         .withOldScripts(initialScripts)
@@ -98,8 +101,13 @@ describe('CodeChangedEvent', () => {
   describe('removedScripts', () => {
     it('returns removed scripts when script are removed', () => {
       // arrange
-      const existingScripts = [new SelectedScriptStub('0'), new SelectedScriptStub('1')];
-      const removedScripts = [new SelectedScriptStub('2')];
+      const existingScripts = [
+        new SelectedScriptStub(new ScriptStub('0')),
+        new SelectedScriptStub(new ScriptStub('1')),
+      ];
+      const removedScripts = [
+        new SelectedScriptStub(new ScriptStub('2')),
+      ];
       const initialScripts = [...existingScripts, ...removedScripts];
       const newScripts = new Map<SelectedScript, ICodePosition>([
         [initialScripts[0], new CodePosition(0, 1)],
@@ -119,10 +127,17 @@ describe('CodeChangedEvent', () => {
   describe('changedScripts', () => {
     it('returns changed scripts when scripts are changed', () => {
       // arrange
-      const initialScripts = [new SelectedScriptStub('1', false), new SelectedScriptStub('2', false)];
+      const changedScripts = [
+        new ScriptStub('scripts-with-changed-selection-1'),
+        new ScriptStub('scripts-with-changed-selection-2'),
+      ];
+      const initialScripts = [
+        new SelectedScriptStub(changedScripts[0]).withRevert(false),
+        new SelectedScriptStub(changedScripts[1]).withRevert(false),
+      ];
       const newScripts = new Map<SelectedScript, ICodePosition>([
-        [new SelectedScriptStub('1', true), new CodePosition(0, 1)],
-        [new SelectedScriptStub('2', false), new CodePosition(0, 1)],
+        [new SelectedScriptStub(changedScripts[0]).withRevert(true), new CodePosition(0, 1)],
+        [new SelectedScriptStub(changedScripts[1]).withRevert(false), new CodePosition(0, 1)],
       ]);
       const sut = new CodeChangedEventBuilder()
         .withOldScripts(initialScripts)
@@ -139,7 +154,7 @@ describe('CodeChangedEvent', () => {
     it('returns true when empty', () => {
       // arrange
       const newScripts = new Map<SelectedScript, ICodePosition>();
-      const oldScripts = [new SelectedScriptStub('1', false)];
+      const oldScripts = [new SelectedScriptStub(new ScriptStub('1')).withRevert(false)];
       const sut = new CodeChangedEventBuilder()
         .withOldScripts(oldScripts)
         .withNewScripts(newScripts)
@@ -151,7 +166,7 @@ describe('CodeChangedEvent', () => {
     });
     it('returns false when not empty', () => {
       // arrange
-      const oldScripts = [new SelectedScriptStub('1')];
+      const oldScripts = [new SelectedScriptStub(new ScriptStub('1'))];
       const newScripts = new Map<SelectedScript, ICodePosition>([
         [oldScripts[0], new CodePosition(0, 1)],
       ]);
@@ -182,7 +197,7 @@ describe('CodeChangedEvent', () => {
       const script = new ScriptStub('1');
       const expected = new CodePosition(0, 1);
       const newScripts = new Map<SelectedScript, ICodePosition>([
-        [new SelectedScript(script, false), expected],
+        [new SelectedScriptStub(script).withRevert(false), expected],
       ]);
       const sut = new CodeChangedEventBuilder()
         .withNewScripts(newScripts)
diff --git a/tests/unit/application/Context/State/Code/Generation/UserScriptGenerator.spec.ts b/tests/unit/application/Context/State/Code/Generation/UserScriptGenerator.spec.ts
index b7f5f64b..bc4f8710 100644
--- a/tests/unit/application/Context/State/Code/Generation/UserScriptGenerator.spec.ts
+++ b/tests/unit/application/Context/State/Code/Generation/UserScriptGenerator.spec.ts
@@ -1,12 +1,12 @@
 import { describe, it, expect } from 'vitest';
 import { UserScriptGenerator } from '@/application/Context/State/Code/Generation/UserScriptGenerator';
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
 import { ICodeBuilderFactory } from '@/application/Context/State/Code/Generation/ICodeBuilderFactory';
 import { ICodeBuilder } from '@/application/Context/State/Code/Generation/ICodeBuilder';
 import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
 import { ScriptingDefinitionStub } from '@tests/unit/shared/Stubs/ScriptingDefinitionStub';
 import { itEachAbsentStringValue } from '@tests/unit/shared/TestCases/AbsentTests';
 import { expectExists } from '@tests/shared/Assertions/ExpectExists';
+import { SelectedScriptStub } from '@tests/unit/shared/Stubs/SelectedScriptStub';
 
 describe('UserScriptGenerator', () => {
   describe('scriptingDefinition', () => {
@@ -94,7 +94,7 @@ describe('UserScriptGenerator', () => {
       const scriptName = 'test non-revert script';
       const scriptCode = 'REM nop';
       const script = new ScriptStub('id').withName(scriptName).withCode(scriptCode);
-      const selectedScripts = [new SelectedScript(script, false)];
+      const selectedScripts = [new SelectedScriptStub(script).withRevert(false)];
       const definition = new ScriptingDefinitionStub();
       // act
       const actual = sut.buildCode(selectedScripts, definition);
@@ -113,7 +113,8 @@ describe('UserScriptGenerator', () => {
       const script = new ScriptStub('id')
         .withName(scriptName)
         .withRevertCode(scriptCode)
-        .toSelectedScript(true);
+        .toSelectedScript()
+        .withRevert(true);
       const definition = new ScriptingDefinitionStub();
       // act
       const actual = sut.buildCode([script], definition);
@@ -127,10 +128,9 @@ describe('UserScriptGenerator', () => {
         const expectedError = 'Reverted script lacks revert code.';
         const sut = new UserScriptGenerator();
         const script = new ScriptStub('id')
-          .toSelectedScript(true);
-        // Hack until SelectedScript is interface:
-        // eslint-disable-next-line @typescript-eslint/no-explicit-any
-        (script.script.code as any).revert = emptyRevertCode;
+          .withRevertCode(emptyRevertCode)
+          .toSelectedScript()
+          .withRevert(true);
         const definition = new ScriptingDefinitionStub();
         // act
         const act = () => sut.buildCode([script], definition);
@@ -181,7 +181,8 @@ describe('UserScriptGenerator', () => {
             const selectedScript = new ScriptStub('script-id')
               .withName('script')
               .withCode(testCase.scriptCode)
-              .toSelectedScript(false);
+              .toSelectedScript()
+              .withRevert(false);
             // act
             const actual = sut.buildCode([selectedScript], definition);
             // expect
diff --git a/tests/unit/application/Context/State/Selection/Category/ScriptToCategorySelectionMapper.spec.ts b/tests/unit/application/Context/State/Selection/Category/ScriptToCategorySelectionMapper.spec.ts
new file mode 100644
index 00000000..1960bf59
--- /dev/null
+++ b/tests/unit/application/Context/State/Selection/Category/ScriptToCategorySelectionMapper.spec.ts
@@ -0,0 +1,272 @@
+import { CategoryStub } from '@tests/unit/shared/Stubs/CategoryStub';
+import { CategoryCollectionStub } from '@tests/unit/shared/Stubs/CategoryCollectionStub';
+import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
+import { ScriptSelection } from '@/application/Context/State/Selection/Script/ScriptSelection';
+import { ICategoryCollection } from '@/domain/ICategoryCollection';
+import { ScriptToCategorySelectionMapper } from '@/application/Context/State/Selection/Category/ScriptToCategorySelectionMapper';
+import { ScriptSelectionStub } from '@tests/unit/shared/Stubs/ScriptSelectionStub';
+import { CategorySelectionChange } from '@/application/Context/State/Selection/Category/CategorySelectionChange';
+import { ScriptSelectionChange, ScriptSelectionChangeCommand } from '@/application/Context/State/Selection/Script/ScriptSelectionChange';
+import { expectExists } from '@tests/shared/Assertions/ExpectExists';
+import { ICategory, IScript } from '@/domain/ICategory';
+
+describe('ScriptToCategorySelectionMapper', () => {
+  describe('areAllScriptsSelected', () => {
+    it('should return false for partially selected scripts', () => {
+      // arrange
+      const expected = false;
+      const { sut, category } = setupTestWithPreselectedScripts({
+        preselect: (allScripts) => [allScripts[0]],
+      });
+      // act
+      const actual = sut.areAllScriptsSelected(category);
+      // assert
+      expect(actual).to.equal(expected);
+    });
+    it('should return true when all scripts are selected', () => {
+      // arrange
+      const expected = true;
+      const { sut, category } = setupTestWithPreselectedScripts({
+        preselect: (allScripts) => [...allScripts],
+      });
+      // act
+      const actual = sut.areAllScriptsSelected(category);
+      // assert
+      expect(actual).to.equal(expected);
+    });
+  });
+  describe('isAnyScriptSelected', () => {
+    it('should return false with no selected scripts', () => {
+      // arrange
+      const expected = false;
+      const { sut, category } = setupTestWithPreselectedScripts({
+        preselect: () => [],
+      });
+      // act
+      const actual = sut.isAnyScriptSelected(category);
+      // assert
+      expect(actual).to.equal(expected);
+    });
+    it('should return true with at least one script selected', () => {
+      // arrange
+      const expected = true;
+      const { sut, category } = setupTestWithPreselectedScripts({
+        preselect: (allScripts) => [allScripts[0]],
+      });
+      // act
+      const actual = sut.isAnyScriptSelected(category);
+      // assert
+      expect(actual).to.equal(expected);
+    });
+  });
+  describe('processChanges', () => {
+    const testScenarios: ReadonlyArray<{
+      readonly description: string;
+      readonly changes: readonly CategorySelectionChange[];
+      readonly categories: ReadonlyArray<{
+        readonly categoryId: ICategory['id'],
+        readonly scriptIds: readonly IScript['id'][],
+      }>;
+      readonly expected: readonly ScriptSelectionChange[],
+    }> = [
+      {
+        description: 'single script: select without revert',
+        categories: [
+          { categoryId: 1, scriptIds: ['single-script'] },
+        ],
+        changes: [
+          { categoryId: 1, newStatus: { isSelected: true, isReverted: false } },
+        ],
+        expected: [
+          { scriptId: 'single-script', newStatus: { isSelected: true, isReverted: false } },
+        ],
+      },
+      {
+        description: 'multiple scripts: select without revert',
+        categories: [
+          { categoryId: 1, scriptIds: ['script1-cat1', 'script2-cat1'] },
+          { categoryId: 2, scriptIds: ['script3-cat2'] },
+        ],
+        changes: [
+          { categoryId: 1, newStatus: { isSelected: true, isReverted: false } },
+          { categoryId: 2, newStatus: { isSelected: true, isReverted: false } },
+        ],
+        expected: [
+          { scriptId: 'script1-cat1', newStatus: { isSelected: true, isReverted: false } },
+          { scriptId: 'script2-cat1', newStatus: { isSelected: true, isReverted: false } },
+          { scriptId: 'script3-cat2', newStatus: { isSelected: true, isReverted: false } },
+        ],
+      },
+      {
+        description: 'single script: select with revert',
+        categories: [
+          { categoryId: 1, scriptIds: ['single-script'] },
+        ],
+        changes: [
+          { categoryId: 1, newStatus: { isSelected: true, isReverted: true } },
+        ],
+        expected: [
+          { scriptId: 'single-script', newStatus: { isSelected: true, isReverted: true } },
+        ],
+      },
+      {
+        description: 'multiple scripts: select with revert',
+        categories: [
+          { categoryId: 1, scriptIds: ['script-1-cat-1'] },
+          { categoryId: 2, scriptIds: ['script-2-cat-2'] },
+          { categoryId: 3, scriptIds: ['script-3-cat-3'] },
+        ],
+        changes: [
+          { categoryId: 1, newStatus: { isSelected: true, isReverted: true } },
+          { categoryId: 2, newStatus: { isSelected: true, isReverted: true } },
+          { categoryId: 3, newStatus: { isSelected: true, isReverted: true } },
+        ],
+        expected: [
+          { scriptId: 'script-1-cat-1', newStatus: { isSelected: true, isReverted: true } },
+          { scriptId: 'script-2-cat-2', newStatus: { isSelected: true, isReverted: true } },
+          { scriptId: 'script-3-cat-3', newStatus: { isSelected: true, isReverted: true } },
+        ],
+      },
+      {
+        description: 'single script: deselect',
+        categories: [
+          { categoryId: 1, scriptIds: ['single-script'] },
+        ],
+        changes: [
+          { categoryId: 1, newStatus: { isSelected: false } },
+        ],
+        expected: [
+          { scriptId: 'single-script', newStatus: { isSelected: false } },
+        ],
+      },
+      {
+        description: 'multiple scripts: deselect',
+        categories: [
+          { categoryId: 1, scriptIds: ['script-1-cat1'] },
+          { categoryId: 2, scriptIds: ['script-2-cat2'] },
+        ],
+        changes: [
+          { categoryId: 1, newStatus: { isSelected: false } },
+          { categoryId: 2, newStatus: { isSelected: false } },
+        ],
+        expected: [
+          { scriptId: 'script-1-cat1', newStatus: { isSelected: false } },
+          { scriptId: 'script-2-cat2', newStatus: { isSelected: false } },
+        ],
+      },
+      {
+        description: 'mixed operations (select, revert, deselect)',
+        categories: [
+          { categoryId: 1, scriptIds: ['to-revert'] },
+          { categoryId: 2, scriptIds: ['not-revert'] },
+          { categoryId: 3, scriptIds: ['to-deselect'] },
+        ],
+        changes: [
+          { categoryId: 1, newStatus: { isSelected: true, isReverted: true } },
+          { categoryId: 2, newStatus: { isSelected: true, isReverted: false } },
+          { categoryId: 3, newStatus: { isSelected: false } },
+        ],
+        expected: [
+          { scriptId: 'to-revert', newStatus: { isSelected: true, isReverted: true } },
+          { scriptId: 'not-revert', newStatus: { isSelected: true, isReverted: false } },
+          { scriptId: 'to-deselect', newStatus: { isSelected: false } },
+        ],
+      },
+      {
+        description: 'affecting selected categories only',
+        categories: [
+          { categoryId: 1, scriptIds: ['relevant-1', 'relevant-2'] },
+          { categoryId: 2, scriptIds: ['not-relevant-1', 'not-relevant-2'] },
+          { categoryId: 3, scriptIds: ['not-relevant-3', 'not-relevant-4'] },
+        ],
+        changes: [
+          { categoryId: 1, newStatus: { isSelected: true, isReverted: true } },
+        ],
+        expected: [
+          { scriptId: 'relevant-1', newStatus: { isSelected: true, isReverted: true } },
+          { scriptId: 'relevant-2', newStatus: { isSelected: true, isReverted: true } },
+        ],
+      },
+    ];
+    testScenarios.forEach(({
+      description, changes, categories, expected,
+    }) => {
+      it(description, () => {
+        // arrange
+        const scriptSelectionStub = new ScriptSelectionStub();
+        const sut = new ScriptToCategorySelectionMapperBuilder()
+          .withScriptSelection(scriptSelectionStub)
+          .withCollection(new CategoryCollectionStub().withAction(
+            new CategoryStub(99)
+              // Register scripts to test for nested items
+              .withAllScriptIdsRecursively(...categories.flatMap((c) => c.scriptIds))
+              .withCategories(...categories.map(
+                (c) => new CategoryStub(c.categoryId).withAllScriptIdsRecursively(...c.scriptIds),
+              )),
+          ))
+          .build();
+        // act
+        sut.processChanges({
+          changes,
+        });
+        // assert
+        expect(scriptSelectionStub.callHistory).to.have.lengthOf(1);
+        const call = scriptSelectionStub.callHistory.find((m) => m.methodName === 'processChanges');
+        expectExists(call);
+        const [command] = call.args;
+        const { changes: actualChanges } = (command as ScriptSelectionChangeCommand);
+        expect(actualChanges).to.have.lengthOf(expected.length);
+        expect(actualChanges).to.deep.members(expected);
+      });
+    });
+  });
+});
+
+class ScriptToCategorySelectionMapperBuilder {
+  private scriptSelection: ScriptSelection = new ScriptSelectionStub();
+
+  private collection: ICategoryCollection = new CategoryCollectionStub();
+
+  public withScriptSelection(scriptSelection: ScriptSelection): this {
+    this.scriptSelection = scriptSelection;
+    return this;
+  }
+
+  public withCollection(collection: ICategoryCollection): this {
+    this.collection = collection;
+    return this;
+  }
+
+  public build(): ScriptToCategorySelectionMapper {
+    return new ScriptToCategorySelectionMapper(
+      this.scriptSelection,
+      this.collection,
+    );
+  }
+}
+
+type TestScripts = readonly [ScriptStub, ScriptStub, ScriptStub];
+function setupTestWithPreselectedScripts(options: {
+  preselect: (allScripts: TestScripts) => readonly ScriptStub[],
+}) {
+  const allScripts: TestScripts = [
+    new ScriptStub('first-script'),
+    new ScriptStub('second-script'),
+    new ScriptStub('third-script'),
+  ];
+  const preselectedScripts = options.preselect(allScripts);
+  const category = new CategoryStub(1)
+    .withAllScriptsRecursively(...allScripts); // Register scripts to test for nested items
+  const collection = new CategoryCollectionStub().withAction(category);
+  const sut = new ScriptToCategorySelectionMapperBuilder()
+    .withCollection(collection)
+    .withScriptSelection(
+      new ScriptSelectionStub()
+        .withSelectedScripts(preselectedScripts.map((s) => s.toSelectedScript())),
+    )
+    .build();
+  return {
+    category,
+    sut,
+  };
+}
diff --git a/tests/unit/application/Context/State/Selection/Script/DebouncedScriptSelection.spec.ts b/tests/unit/application/Context/State/Selection/Script/DebouncedScriptSelection.spec.ts
new file mode 100644
index 00000000..606d60bc
--- /dev/null
+++ b/tests/unit/application/Context/State/Selection/Script/DebouncedScriptSelection.spec.ts
@@ -0,0 +1,628 @@
+import { describe, it, expect } from 'vitest';
+import { DebounceFunction, DebouncedScriptSelection } from '@/application/Context/State/Selection/Script/DebouncedScriptSelection';
+import { CategoryStub } from '@tests/unit/shared/Stubs/CategoryStub';
+import { CategoryCollectionStub } from '@tests/unit/shared/Stubs/CategoryCollectionStub';
+import { SelectedScriptStub } from '@tests/unit/shared/Stubs/SelectedScriptStub';
+import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
+import { ICategoryCollection } from '@/domain/ICategoryCollection';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
+import { BatchedDebounceStub } from '@tests/unit/shared/Stubs/BatchedDebounceStub';
+import { ScriptSelectionChange, ScriptSelectionChangeCommand } from '@/application/Context/State/Selection/Script/ScriptSelectionChange';
+import { expectExists } from '@tests/shared/Assertions/ExpectExists';
+import { IScript } from '@/domain/IScript';
+import { expectEqualSelectedScripts } from './ExpectEqualSelectedScripts';
+
+type DebounceArg = ScriptSelectionChangeCommand;
+
+describe('DebouncedScriptSelection', () => {
+  describe('constructor', () => {
+    describe('initialization of selected scripts', () => {
+      const testScenarios: ReadonlyArray<{
+        readonly description: string;
+        readonly selectedScripts: readonly SelectedScript[];
+      }> = [
+        {
+          description: 'initializes with no scripts when given empty array',
+          selectedScripts: [],
+        },
+        {
+          description: 'initializes with a single script when given one script',
+          selectedScripts: [new SelectedScriptStub(new ScriptStub('s1'))],
+        },
+        {
+          description: 'initializes with multiple scripts when given multiple scripts',
+          selectedScripts: [
+            new SelectedScriptStub(new ScriptStub('s1')),
+            new SelectedScriptStub(new ScriptStub('s2')),
+          ],
+        },
+      ];
+      testScenarios.forEach(({ description, selectedScripts }) => {
+        it(description, () => {
+          // arrange
+          const expectedScripts = selectedScripts;
+          const builder = new DebouncedScriptSelectionBuilder()
+            .withSelectedScripts(selectedScripts);
+          // act
+          const selection = builder.build();
+          const actualScripts = selection.selectedScripts;
+          // assert
+          expectEqualSelectedScripts(actualScripts, expectedScripts);
+        });
+      });
+    });
+    describe('debounce configuration', () => {
+      /*
+        Note: These tests cover internal implementation details, particularly the debouncing logic,
+        to ensure comprehensive code coverage. They are not focused on the public API. While useful
+        for detecting subtle bugs, they might need updates during refactoring if internal structures
+        change but external behaviors remain the same.
+      */
+      it('sets up debounce with a callback function', () => {
+        // arrange
+        const debounceStub = new BatchedDebounceStub<DebounceArg>();
+        const builder = new DebouncedScriptSelectionBuilder()
+          .withBatchedDebounce(debounceStub.func);
+        // act
+        builder.build();
+        // assert
+        expect(debounceStub.callHistory).to.have.lengthOf(1);
+        const [debounceFunc] = debounceStub.callHistory[0];
+        expectExists(debounceFunc);
+      });
+      it('configures debounce with specific delay ', () => {
+        // arrange
+        const expectedDebounceInMs = 100;
+        const debounceStub = new BatchedDebounceStub<DebounceArg>();
+        const builder = new DebouncedScriptSelectionBuilder()
+          .withBatchedDebounce(debounceStub.func);
+        // act
+        builder.build();
+        // assert
+        expect(debounceStub.callHistory).to.have.lengthOf(1);
+        const [, waitInMs] = debounceStub.callHistory[0];
+        expect(waitInMs).to.equal(expectedDebounceInMs);
+      });
+      it('applies debouncing to processChanges method', () => {
+        // arrange
+        const expectedFunc = () => {};
+        const debounceMock: DebounceFunction = () => expectedFunc;
+        const builder = new DebouncedScriptSelectionBuilder()
+          .withBatchedDebounce(debounceMock);
+        // act
+        const selection = builder.build();
+        // assert
+        const actualFunction = selection.processChanges;
+        expect(actualFunction).to.equal(expectedFunc);
+      });
+    });
+  });
+  describe('isSelected', () => {
+    it('returns false for an unselected script', () => {
+      // arrange
+      const expectedResult = false;
+      const { scriptSelection, unselectedScripts } = setupTestWithPreselectedScripts({
+        preselect: (allScripts) => [allScripts[0]],
+      });
+      const scriptIdToCheck = unselectedScripts[0].id;
+      // act
+      const actual = scriptSelection.isSelected(scriptIdToCheck);
+      // assert
+      expect(actual).to.equal(expectedResult);
+    });
+    it('returns true for a selected script', () => {
+      // arrange
+      const expectedResult = true;
+      const { scriptSelection, preselectedScripts } = setupTestWithPreselectedScripts({
+        preselect: (allScripts) => [allScripts[0]],
+      });
+      const scriptIdToCheck = preselectedScripts[0].id;
+      // act
+      const actual = scriptSelection.isSelected(scriptIdToCheck);
+      // assert
+      expect(actual).to.equal(expectedResult);
+    });
+  });
+  describe('deselectAll', () => {
+    it('removes all selected scripts', () => {
+      // arrange
+      const { scriptSelection, changeEvents } = setupTestWithPreselectedScripts({
+        preselect: (scripts) => [scripts[0], scripts[1]],
+      });
+      // act
+      scriptSelection.deselectAll();
+      // assert
+      expect(changeEvents).to.have.lengthOf(1);
+      expect(changeEvents[0]).to.have.lengthOf(0);
+      expect(scriptSelection.selectedScripts).to.have.lengthOf(0);
+    });
+    it('does not notify when no scripts are selected', () => {
+      // arrange
+      const { scriptSelection, changeEvents } = setupTestWithPreselectedScripts({
+        preselect: () => [],
+      });
+      // act
+      scriptSelection.deselectAll();
+      // assert
+      expect(changeEvents).to.have.lengthOf(0);
+      expect(scriptSelection.selectedScripts).to.have.lengthOf(0);
+    });
+  });
+  describe('selectAll', () => {
+    it('selects all available scripts', () => {
+      // arrange
+      const selectedRevertState = false;
+      const { scriptSelection, changeEvents, allScripts } = setupTestWithPreselectedScripts({
+        preselect: () => [],
+      });
+      const expectedSelection = allScripts.map(
+        (s) => s.toSelectedScript().withRevert(selectedRevertState),
+      );
+      // act
+      scriptSelection.selectAll();
+      // assert
+      expect(changeEvents).to.have.lengthOf(1);
+      expectEqualSelectedScripts(changeEvents[0], expectedSelection);
+      expectEqualSelectedScripts(scriptSelection.selectedScripts, expectedSelection);
+    });
+    it('does not notify when no new scripts are selected', () => {
+      // arrange
+      const { scriptSelection, changeEvents } = setupTestWithPreselectedScripts({
+        preselect: (allScripts) => allScripts,
+      });
+      // act
+      scriptSelection.selectAll();
+      // assert
+      expect(changeEvents).to.have.lengthOf(0);
+    });
+  });
+  describe('selectOnly', () => {
+    describe('selects correctly', () => {
+      const testScenarios: ReadonlyArray<{
+        readonly description: string;
+        readonly preselect: (allScripts: TestScripts) => readonly SelectedScriptStub[],
+        readonly toSelect: (allScripts: TestScripts) => readonly ScriptStub[];
+        readonly getExpectedFinalSelection: (allScripts: TestScripts) => readonly SelectedScript[],
+      }> = [
+        {
+          description: 'adds expected scripts to empty selection as non-reverted',
+          preselect: () => [],
+          toSelect: (allScripts) => [allScripts[0]],
+          getExpectedFinalSelection: (allScripts) => [
+            allScripts[0].toSelectedScript().withRevert(false),
+          ],
+        },
+        {
+          description: 'adds expected scripts to existing selection as non-reverted',
+          preselect: (allScripts) => [allScripts[0], allScripts[1]]
+            .map((s) => s.toSelectedScript().withRevert(false)),
+          toSelect: (allScripts) => [...allScripts],
+          getExpectedFinalSelection: (allScripts) => allScripts
+            .map((s) => s.toSelectedScript().withRevert(false)),
+        },
+        {
+          description: 'removes other scripts from selection',
+          preselect: (allScripts) => allScripts
+            .map((s) => s.toSelectedScript().withRevert(false)),
+          toSelect: (allScripts) => [allScripts[0]],
+          getExpectedFinalSelection: (allScripts) => [
+            allScripts[0].toSelectedScript().withRevert(false),
+          ],
+        },
+        {
+          description: 'handles both addition and removal of scripts correctly',
+          preselect: (allScripts) => [allScripts[0], allScripts[2]] // Removes "2"
+            .map((s) => s.toSelectedScript().withRevert(false)),
+          toSelect: (allScripts) => [allScripts[0], allScripts[1]], // Adds "1"
+          getExpectedFinalSelection: (allScripts) => [
+            allScripts[0].toSelectedScript().withRevert(false),
+            allScripts[1].toSelectedScript().withRevert(false),
+          ],
+        },
+      ];
+      testScenarios.forEach(({
+        description, preselect, toSelect, getExpectedFinalSelection,
+      }) => {
+        it(description, () => {
+          // arrange
+          const { scriptSelection, changeEvents, allScripts } = setupTestWithPreselectedScripts({
+            preselect,
+          });
+          const scriptsToSelect = toSelect(allScripts);
+          const expectedSelection = getExpectedFinalSelection(allScripts);
+          // act
+          scriptSelection.selectOnly(scriptsToSelect);
+          // assert
+          expect(changeEvents).to.have.lengthOf(1);
+          expectEqualSelectedScripts(changeEvents[0], expectedSelection);
+          expectEqualSelectedScripts(scriptSelection.selectedScripts, expectedSelection);
+        });
+      });
+    });
+    describe('does not notify for unchanged selection', () => {
+      const testScenarios: ReadonlyArray<{
+        readonly description: string;
+        readonly preselect: TestScriptSelector;
+      }> = [
+        {
+          description: 'unchanged selection with reverted scripts',
+          preselect: (allScripts) => allScripts.map((s) => s.toSelectedScript().withRevert(true)),
+        },
+        {
+          description: 'unchanged selection with non-reverted scripts',
+          preselect: (allScripts) => allScripts.map((s) => s.toSelectedScript().withRevert(false)),
+        },
+        {
+          description: 'unchanged selection with mixed revert states',
+          preselect: (allScripts) => [
+            allScripts[0].toSelectedScript().withRevert(true),
+            allScripts[1].toSelectedScript().withRevert(false),
+          ],
+        },
+      ];
+      testScenarios.forEach(({
+        description, preselect,
+      }) => {
+        it(description, () => {
+          // arrange
+          const {
+            scriptSelection, changeEvents, preselectedScripts,
+          } = setupTestWithPreselectedScripts({ preselect });
+          const scriptsToSelect = preselectedScripts.map((s) => s.script);
+          // act
+          scriptSelection.selectOnly(scriptsToSelect);
+          // assert
+          expect(changeEvents).to.have.lengthOf(0);
+        });
+      });
+    });
+    it('throws error when an empty script array is passed', () => {
+      // arrange
+      const expectedError = 'Provided script array is empty. To deselect all scripts, please use the deselectAll() method instead.';
+      const scripts = [];
+      const scriptSelection = new DebouncedScriptSelectionBuilder().build();
+      // act
+      const act = () => scriptSelection.selectOnly(scripts);
+      // assert
+      expect(act).to.throw(expectedError);
+    });
+  });
+  describe('processChanges', () => {
+    describe('mutates correctly', () => {
+      const testScenarios: ReadonlyArray<{
+        readonly description: string;
+        readonly preselect: TestScriptSelector;
+        readonly getChanges: (allScripts: TestScripts) => readonly ScriptSelectionChange[];
+        readonly getExpectedFinalSelection: (allScripts: TestScripts) => readonly SelectedScript[],
+      }> = [
+        {
+          description: 'correctly adds a new reverted script',
+          preselect: (allScripts) => [allScripts[0], allScripts[1]]
+            .map((s) => s.toSelectedScript()),
+          getChanges: (allScripts) => [
+            { scriptId: allScripts[2].id, newStatus: { isReverted: true, isSelected: true } },
+          ],
+          getExpectedFinalSelection: (allScripts) => [
+            allScripts[0].toSelectedScript(),
+            allScripts[1].toSelectedScript(),
+            new SelectedScriptStub(allScripts[2]).withRevert(true),
+          ],
+        },
+        {
+          description: 'correctly adds a new non-reverted script',
+          preselect: (allScripts) => [allScripts[0], allScripts[1]]
+            .map((s) => s.toSelectedScript()),
+          getChanges: (allScripts) => [
+            { scriptId: allScripts[2].id, newStatus: { isReverted: false, isSelected: true } },
+          ],
+          getExpectedFinalSelection: (allScripts) => [
+            allScripts[0].toSelectedScript(),
+            allScripts[1].toSelectedScript(),
+            new SelectedScriptStub(allScripts[2]).withRevert(false),
+          ],
+        },
+        {
+          description: 'correctly removes an existing script',
+          preselect: (allScripts) => [allScripts[0], allScripts[1]]
+            .map((s) => s.toSelectedScript()),
+          getChanges: (allScripts) => [
+            { scriptId: allScripts[0].id, newStatus: { isSelected: false } },
+          ],
+          getExpectedFinalSelection: (allScripts) => [
+            allScripts[1].toSelectedScript(),
+          ],
+        },
+        {
+          description: 'updates revert status to true for an existing script',
+          preselect: (allScripts) => [
+            allScripts[0].toSelectedScript().withRevert(false),
+            allScripts[1].toSelectedScript(),
+          ],
+          getChanges: (allScripts) => [
+            { scriptId: allScripts[0].id, newStatus: { isSelected: true, isReverted: true } },
+          ],
+          getExpectedFinalSelection: (allScripts) => [
+            allScripts[0].toSelectedScript().withRevert(true),
+            allScripts[1].toSelectedScript(),
+          ],
+        },
+        {
+          description: 'updates revert status to false for an existing script',
+          preselect: (allScripts) => [
+            allScripts[0].toSelectedScript().withRevert(true),
+            allScripts[1].toSelectedScript(),
+          ],
+          getChanges: (allScripts) => [
+            { scriptId: allScripts[0].id, newStatus: { isSelected: true, isReverted: false } },
+          ],
+          getExpectedFinalSelection: (allScripts) => [
+            allScripts[0].toSelectedScript().withRevert(false),
+            allScripts[1].toSelectedScript(),
+          ],
+        },
+        {
+          description: 'handles mixed operations: add, update, remove',
+          preselect: (allScripts) => [
+            allScripts[0].toSelectedScript().withRevert(true), // update
+            allScripts[2].toSelectedScript(), // remove
+          ],
+          getChanges: (allScripts) => [
+            { scriptId: allScripts[0].id, newStatus: { isSelected: true, isReverted: false } },
+            { scriptId: allScripts[1].id, newStatus: { isSelected: true, isReverted: true } },
+            { scriptId: allScripts[2].id, newStatus: { isSelected: false } },
+          ],
+          getExpectedFinalSelection: (allScripts) => [
+            allScripts[0].toSelectedScript().withRevert(false),
+            allScripts[1].toSelectedScript().withRevert(true),
+          ],
+        },
+      ];
+      testScenarios.forEach(({
+        description, preselect, getChanges, getExpectedFinalSelection,
+      }) => {
+        it(description, () => {
+          // arrange
+          const { scriptSelection, changeEvents, allScripts } = setupTestWithPreselectedScripts({
+            preselect,
+          });
+          const changes = getChanges(allScripts);
+          // act
+          scriptSelection.processChanges({
+            changes,
+          });
+          // assert
+          const expectedSelection = getExpectedFinalSelection(allScripts);
+          expect(changeEvents).to.have.lengthOf(1);
+          expectEqualSelectedScripts(changeEvents[0], expectedSelection);
+          expectEqualSelectedScripts(scriptSelection.selectedScripts, expectedSelection);
+        });
+      });
+    });
+    describe('does not mutate for unchanged data', () => {
+      const testScenarios: ReadonlyArray<{
+        readonly description: string;
+        readonly preselect: TestScriptSelector;
+        readonly getChanges: (allScripts: TestScripts) => readonly ScriptSelectionChange[];
+      }> = [
+        {
+          description: 'does not change selection for an already selected script',
+          preselect: (allScripts) => [allScripts[0].toSelectedScript().withRevert(true)],
+          getChanges: (allScripts) => [
+            { scriptId: allScripts[0].id, newStatus: { isReverted: true, isSelected: true } },
+          ],
+        },
+        {
+          description: 'does not change selection when deselecting a missing script',
+          preselect: (allScripts) => [allScripts[0], allScripts[1]]
+            .map((s) => s.toSelectedScript()),
+          getChanges: (allScripts) => [
+            { scriptId: allScripts[2].id, newStatus: { isSelected: false } },
+          ],
+        },
+        {
+          description: 'handles no mutations for mixed unchanged operations',
+          preselect: (allScripts) => [allScripts[0].toSelectedScript().withRevert(false)],
+          getChanges: (allScripts) => [
+            { scriptId: allScripts[0].id, newStatus: { isSelected: true, isReverted: false } },
+            { scriptId: allScripts[1].id, newStatus: { isSelected: false } },
+          ],
+        },
+      ];
+      testScenarios.forEach(({
+        description, preselect, getChanges,
+      }) => {
+        it(description, () => {
+          // arrange
+          const { scriptSelection, changeEvents, allScripts } = setupTestWithPreselectedScripts({
+            preselect,
+          });
+          const initialSelection = [...scriptSelection.selectedScripts];
+          const changes = getChanges(allScripts);
+          // act
+          scriptSelection.processChanges({
+            changes,
+          });
+          // assert
+          expect(changeEvents).to.have.lengthOf(0);
+          expectEqualSelectedScripts(scriptSelection.selectedScripts, initialSelection);
+        });
+      });
+    });
+    describe('debouncing', () => {
+      it('queues commands for debouncing', () => {
+        // arrange
+        const debounceStub = new BatchedDebounceStub<DebounceArg>();
+        const script = new ScriptStub('test');
+        const selection = new DebouncedScriptSelectionBuilder()
+          .withBatchedDebounce(debounceStub.func)
+          .withCollection(createCollectionWithScripts(script))
+          .build();
+        const expectedCommand: ScriptSelectionChangeCommand = {
+          changes: [
+            { scriptId: script.id, newStatus: { isReverted: true, isSelected: true } },
+          ],
+        };
+        // act
+        selection.processChanges(expectedCommand);
+        // assert
+        expect(debounceStub.collectedArgs).to.have.lengthOf(1);
+        expect(debounceStub.collectedArgs[0]).to.equal(expectedCommand);
+      });
+      it('does not apply changes during debouncing period', () => {
+        // arrange
+        const debounceStub = new BatchedDebounceStub<DebounceArg>()
+          .withImmediateDebouncing(false);
+        const script = new ScriptStub('test');
+        const selection = new DebouncedScriptSelectionBuilder()
+          .withBatchedDebounce(debounceStub.func)
+          .withCollection(createCollectionWithScripts(script))
+          .build();
+        const changeEvents = watchForChangeEvents(selection);
+        // act
+        selection.processChanges({
+          changes: [
+            { scriptId: script.id, newStatus: { isReverted: true, isSelected: true } },
+          ],
+        });
+        // assert
+        expect(changeEvents).to.have.lengthOf(0);
+        expectEqualSelectedScripts(selection.selectedScripts, []);
+      });
+      it('applies single change after debouncing period', () => {
+        // arrange
+        const debounceStub = new BatchedDebounceStub<DebounceArg>()
+          .withImmediateDebouncing(false);
+        const script = new ScriptStub('test');
+        const selection = new DebouncedScriptSelectionBuilder()
+          .withBatchedDebounce(debounceStub.func)
+          .withCollection(createCollectionWithScripts(script))
+          .build();
+        const changeEvents = watchForChangeEvents(selection);
+        const expectedSelection = [script.toSelectedScript().withRevert(true)];
+        // act
+        selection.processChanges({
+          changes: [
+            { scriptId: script.id, newStatus: { isReverted: true, isSelected: true } },
+          ],
+        });
+        debounceStub.execute();
+        // assert
+        expect(changeEvents).to.have.lengthOf(1);
+        expectEqualSelectedScripts(selection.selectedScripts, expectedSelection);
+      });
+      it('applies multiple changes after debouncing period', () => {
+        // arrange
+        const debounceStub = new BatchedDebounceStub<DebounceArg>()
+          .withImmediateDebouncing(false);
+        const scripts = [new ScriptStub('first'), new ScriptStub('second'), new ScriptStub('third')];
+        const selection = new DebouncedScriptSelectionBuilder()
+          .withBatchedDebounce(debounceStub.func)
+          .withCollection(createCollectionWithScripts(...scripts))
+          .build();
+        const changeEvents = watchForChangeEvents(selection);
+        const expectedSelection = scripts.map((s) => s.toSelectedScript().withRevert(true));
+        // act
+        for (const script of scripts) {
+          selection.processChanges({
+            changes: [
+              { scriptId: script.id, newStatus: { isReverted: true, isSelected: true } },
+            ],
+          });
+        }
+        debounceStub.execute();
+        // assert
+        expect(changeEvents).to.have.lengthOf(1);
+        expectEqualSelectedScripts(selection.selectedScripts, expectedSelection);
+      });
+    });
+  });
+});
+
+function createCollectionWithScripts(...scripts: IScript[]): CategoryCollectionStub {
+  const category = new CategoryStub(1).withScripts(...scripts);
+  const collection = new CategoryCollectionStub().withAction(category);
+  return collection;
+}
+
+function watchForChangeEvents(
+  selection: DebouncedScriptSelection,
+): ReadonlyArray<readonly SelectedScript[]> {
+  const changes: Array<readonly SelectedScript[]> = [];
+  selection.changed.on((s) => changes.push(s));
+  return changes;
+}
+
+type TestScripts = readonly [ScriptStub, ScriptStub, ScriptStub];
+type TestScriptSelector = (
+  allScripts: TestScripts,
+) => readonly SelectedScriptStub[] | readonly ScriptStub[];
+function setupTestWithPreselectedScripts(options: {
+  preselect: TestScriptSelector,
+}) {
+  const allScripts: TestScripts = [
+    new ScriptStub('first-script'),
+    new ScriptStub('second-script'),
+    new ScriptStub('third-script'),
+  ];
+  const preselectedScripts = (() => {
+    const initialSelection = options.preselect(allScripts);
+    if (isScriptStubArray(initialSelection)) {
+      return initialSelection.map((s) => s.toSelectedScript().withRevert(false));
+    }
+    return initialSelection;
+  })();
+  const unselectedScripts = allScripts.filter(
+    (s) => !preselectedScripts.map((selected) => selected.id).includes(s.id),
+  );
+  const collection = createCollectionWithScripts(...allScripts);
+  const scriptSelection = new DebouncedScriptSelectionBuilder()
+    .withSelectedScripts(preselectedScripts)
+    .withCollection(collection)
+    .build();
+  const changeEvents = watchForChangeEvents(scriptSelection);
+  return {
+    allScripts,
+    unselectedScripts,
+    preselectedScripts,
+    scriptSelection,
+    changeEvents,
+  };
+}
+
+function isScriptStubArray(obj: readonly unknown[]): obj is readonly ScriptStub[] {
+  return obj.length > 0 && obj[0] instanceof ScriptStub;
+}
+
+class DebouncedScriptSelectionBuilder {
+  private collection: ICategoryCollection = new CategoryCollectionStub()
+    .withSomeActions();
+
+  private selectedScripts: readonly SelectedScript[] = [];
+
+  private batchedDebounce: DebounceFunction = new BatchedDebounceStub<DebounceArg>()
+    .withImmediateDebouncing(true)
+    .func;
+
+  public withSelectedScripts(selectedScripts: readonly SelectedScript[]) {
+    this.selectedScripts = selectedScripts;
+    return this;
+  }
+
+  public withBatchedDebounce(batchedDebounce: DebounceFunction) {
+    this.batchedDebounce = batchedDebounce;
+    return this;
+  }
+
+  public withCollection(collection: ICategoryCollection) {
+    this.collection = collection;
+    return this;
+  }
+
+  public build(): DebouncedScriptSelection {
+    return new DebouncedScriptSelection(
+      this.collection,
+      this.selectedScripts,
+      this.batchedDebounce,
+    );
+  }
+}
diff --git a/tests/unit/application/Context/State/Selection/Script/ExpectEqualSelectedScripts.ts b/tests/unit/application/Context/State/Selection/Script/ExpectEqualSelectedScripts.ts
new file mode 100644
index 00000000..98730349
--- /dev/null
+++ b/tests/unit/application/Context/State/Selection/Script/ExpectEqualSelectedScripts.ts
@@ -0,0 +1,46 @@
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
+
+export function expectEqualSelectedScripts(
+  actual: readonly SelectedScript[],
+  expected: readonly SelectedScript[],
+) {
+  expectSameScriptIds(actual, expected);
+  expectSameRevertStates(actual, expected);
+}
+
+function expectSameScriptIds(
+  actual: readonly SelectedScript[],
+  expected: readonly SelectedScript[],
+) {
+  const existingScriptIds = expected.map((script) => script.id).sort();
+  const expectedScriptIds = actual.map((script) => script.id).sort();
+  expect(existingScriptIds).to.deep.equal(expectedScriptIds, [
+    'Unexpected script IDs.',
+    `Expected: ${expectedScriptIds.join(', ')}`,
+    `Actual: ${existingScriptIds.join(', ')}`,
+  ].join('\n'));
+}
+
+function expectSameRevertStates(
+  actual: readonly SelectedScript[],
+  expected: readonly SelectedScript[],
+) {
+  const scriptsWithDifferentRevertStates = actual
+    .filter((script) => {
+      const other = expected.find((existing) => existing.id === script.id);
+      if (!other) {
+        throw new Error(`Script "${script.id}" does not exist in expected scripts: ${JSON.stringify(expected, null, '\t')}`);
+      }
+      return script.revert !== other.revert;
+    });
+  expect(scriptsWithDifferentRevertStates).to.have.lengthOf(0, [
+    'Scripts with different revert states:',
+    scriptsWithDifferentRevertStates
+      .map((s) => [
+        `Script ID: "${s.id}"`,
+        `Actual revert state: "${s.revert}"`,
+        `Expected revert state: "${expected.find((existing) => existing.id === s.id)?.revert ?? 'unknown'}"`,
+      ].map((line) => `\t${line}`).join('\n'))
+      .join('\n---\n'),
+  ].join('\n'));
+}
diff --git a/tests/unit/application/Context/State/Selection/SelectedScript.spec.ts b/tests/unit/application/Context/State/Selection/Script/UserSelectedScript.spec.ts
similarity index 50%
rename from tests/unit/application/Context/State/Selection/SelectedScript.spec.ts
rename to tests/unit/application/Context/State/Selection/Script/UserSelectedScript.spec.ts
index d8a64d76..edc03223 100644
--- a/tests/unit/application/Context/State/Selection/SelectedScript.spec.ts
+++ b/tests/unit/application/Context/State/Selection/Script/UserSelectedScript.spec.ts
@@ -1,13 +1,13 @@
 import { describe, it, expect } from 'vitest';
 import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
+import { UserSelectedScript } from '@/application/Context/State/Selection/Script/UserSelectedScript';
 
-describe('SelectedScript', () => {
+describe('UserSelectedScript', () => {
   it('id is same as script id', () => {
     // arrange
     const expectedId = 'scriptId';
     const script = new ScriptStub(expectedId);
-    const sut = new SelectedScript(script, false);
+    const sut = new UserSelectedScript(script, false);
     // act
     const actualId = sut.id;
     // assert
@@ -15,13 +15,13 @@ describe('SelectedScript', () => {
   });
   it('throws when revert is true for irreversible script', () => {
     // arrange
-    const expectedId = 'scriptId';
-    const script = new ScriptStub(expectedId)
+    const scriptId = 'irreversibleScriptId';
+    const expectedError = `The script with ID '${scriptId}' is not reversible and cannot be reverted.`;
+    const script = new ScriptStub(scriptId)
       .withRevertCode(undefined);
     // act
-    // eslint-disable-next-line no-new
-    function construct() { new SelectedScript(script, true); }
+    const act = () => new UserSelectedScript(script, true);
     // assert
-    expect(construct).to.throw('cannot revert an irreversible script');
+    expect(act).to.throw(expectedError);
   });
 });
diff --git a/tests/unit/application/Context/State/Selection/UserSelection.spec.ts b/tests/unit/application/Context/State/Selection/UserSelection.spec.ts
deleted file mode 100644
index ba0030f8..00000000
--- a/tests/unit/application/Context/State/Selection/UserSelection.spec.ts
+++ /dev/null
@@ -1,463 +0,0 @@
-import { describe, it, expect } from 'vitest';
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
-import { UserSelection } from '@/application/Context/State/Selection/UserSelection';
-import { CategoryStub } from '@tests/unit/shared/Stubs/CategoryStub';
-import { CategoryCollectionStub } from '@tests/unit/shared/Stubs/CategoryCollectionStub';
-import { SelectedScriptStub } from '@tests/unit/shared/Stubs/SelectedScriptStub';
-import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
-import { UserSelectionTestRunner } from './UserSelectionTestRunner';
-
-describe('UserSelection', () => {
-  describe('ctor', () => {
-    describe('has nothing with no initial selection', () => {
-      // arrange
-      const allScripts = [
-        new SelectedScriptStub('s1', false),
-      ];
-      new UserSelectionTestRunner()
-        .withSelectedScripts([])
-        .withCategory(1, allScripts.map((s) => s.script))
-      // act
-        .run()
-      // assert
-        .expectFinalScripts([]);
-    });
-    describe('has initial selection', () => {
-      // arrange
-      const scripts = [
-        new SelectedScriptStub('s1', false),
-        new SelectedScriptStub('s2', false),
-      ];
-      new UserSelectionTestRunner()
-        .withSelectedScripts(scripts)
-        .withCategory(1, scripts.map((s) => s.script))
-      // act
-        .run()
-      // assert
-        .expectFinalScripts(scripts);
-    });
-  });
-  describe('deselectAll', () => {
-    describe('removes existing items', () => {
-      // arrange
-      const allScripts = [
-        new SelectedScriptStub('s1', false),
-        new SelectedScriptStub('s2', false),
-        new SelectedScriptStub('s3', false),
-        new SelectedScriptStub('s4', false),
-      ];
-      const selectedScripts = allScripts.filter(
-        (s) => ['s1', 's2', 's3'].includes(s.id),
-      );
-      new UserSelectionTestRunner()
-        .withSelectedScripts(selectedScripts)
-        .withCategory(1, allScripts.map((s) => s.script))
-      // act
-        .run((sut) => {
-          sut.deselectAll();
-        })
-      // assert
-        .expectTotalFiredEvents(1)
-        .expectFinalScripts([])
-        .expectFinalScriptsInEvent(0, []);
-    });
-    describe('does not notify if nothing is selected', () => {
-      new UserSelectionTestRunner()
-      // arrange
-        .withSelectedScripts([])
-      // act
-        .run((sut) => {
-          sut.deselectAll();
-        })
-      // assert
-        .expectTotalFiredEvents(0);
-    });
-  });
-  describe('selectAll', () => {
-    describe('selects as expected', () => {
-      // arrange
-      const expected = [
-        new SelectedScriptStub('s1', false),
-        new SelectedScriptStub('s2', false),
-      ];
-      new UserSelectionTestRunner()
-        .withSelectedScripts([])
-        .withCategory(1, expected.map((s) => s.script))
-      // act
-        .run((sut) => {
-          sut.selectAll();
-        })
-      // assert
-        .expectTotalFiredEvents(1)
-        .expectFinalScripts(expected)
-        .expectFinalScriptsInEvent(0, expected);
-    });
-    describe('does not notify if nothing new is selected', () => {
-      const allScripts = [new ScriptStub('s1'), new ScriptStub('s2')];
-      const selectedScripts = allScripts.map((s) => s.toSelectedScript(false));
-      new UserSelectionTestRunner()
-      // arrange
-        .withSelectedScripts(selectedScripts)
-        .withCategory(0, allScripts)
-      // act
-        .run((sut) => {
-          sut.selectAll();
-        })
-      // assert
-        .expectTotalFiredEvents(0);
-    });
-  });
-  describe('selectOnly', () => {
-    describe('selects as expected', () => {
-      // arrange
-      const allScripts = [
-        new SelectedScriptStub('s1', false),
-        new SelectedScriptStub('s2', false),
-        new SelectedScriptStub('s3', false),
-        new SelectedScriptStub('s4', false),
-      ];
-      const getScripts = (...ids: string[]) => allScripts.filter((s) => ids.includes(s.id));
-      const testCases = [
-        {
-          name: 'adds as expected',
-          preSelected: getScripts('s1'),
-          toSelect: getScripts('s1', 's2'),
-        },
-        {
-          name: 'removes as expected',
-          preSelected: getScripts('s1', 's2', 's3'),
-          toSelect: getScripts('s1'),
-        },
-        {
-          name: 'adds and removes as expected',
-          preSelected: getScripts('s1', 's2', 's3'),
-          toSelect: getScripts('s2', 's3', 's4'),
-        },
-      ];
-      for (const testCase of testCases) {
-        describe(testCase.name, () => {
-          new UserSelectionTestRunner()
-            .withSelectedScripts(testCase.preSelected)
-            .withCategory(1, testCase.toSelect.map((s) => s.script))
-          // act
-            .run((sut) => {
-              sut.selectOnly(testCase.toSelect.map((s) => s.script));
-            })
-          // assert
-            .expectTotalFiredEvents(1)
-            .expectFinalScripts(testCase.toSelect)
-            .expectFinalScriptsInEvent(0, testCase.toSelect);
-        });
-      }
-    });
-    describe('does not notify if selection does not change', () => {
-      const allScripts = [new ScriptStub('s1'), new ScriptStub('s2'), new ScriptStub('s3')];
-      const toSelect = [allScripts[0], allScripts[1]];
-      const preSelected = toSelect.map((s) => s.toSelectedScript(false));
-      new UserSelectionTestRunner()
-      // arrange
-        .withSelectedScripts(preSelected)
-        .withCategory(0, allScripts)
-      // act
-        .run((sut) => {
-          sut.selectOnly(toSelect);
-        })
-      // assert
-        .expectTotalFiredEvents(0);
-    });
-  });
-  describe('addOrUpdateSelectedScript', () => {
-    describe('adds when item does not exist', () => {
-      // arrange
-      const scripts = [new ScriptStub('s1'), new ScriptStub('s2')];
-      const expected = [new SelectedScript(scripts[0], false)];
-      new UserSelectionTestRunner()
-        .withSelectedScripts([])
-        .withCategory(1, scripts)
-      // act
-        .run((sut) => {
-          sut.addOrUpdateSelectedScript(scripts[0].id, false);
-        })
-      // assert
-        .expectTotalFiredEvents(1)
-        .expectFinalScripts(expected)
-        .expectFinalScriptsInEvent(0, expected);
-    });
-    describe('updates when item exists', () => {
-      // arrange
-      const scripts = [new ScriptStub('s1'), new ScriptStub('s2')];
-      const existing = new SelectedScript(scripts[0], false);
-      const expected = new SelectedScript(scripts[0], true);
-      new UserSelectionTestRunner()
-        .withSelectedScripts([existing])
-        .withCategory(1, scripts)
-      // act
-        .run((sut) => {
-          sut.addOrUpdateSelectedScript(expected.id, expected.revert);
-        })
-      // assert
-        .expectTotalFiredEvents(1)
-        .expectFinalScripts([expected])
-        .expectFinalScriptsInEvent(0, [expected]);
-    });
-  });
-  describe('removeAllInCategory', () => {
-    describe('does nothing when nothing exists', () => {
-      // arrange
-      const categoryId = 99;
-      const scripts = [new ScriptStub('s1'), new ScriptStub('s2')];
-      new UserSelectionTestRunner()
-        .withSelectedScripts([])
-        .withCategory(categoryId, scripts)
-      // act
-        .run((sut) => {
-          sut.removeAllInCategory(categoryId);
-        })
-      // assert
-        .expectTotalFiredEvents(0)
-        .expectFinalScripts([]);
-    });
-    describe('removes all when all exists', () => {
-      // arrange
-      const categoryId = 34;
-      const scripts = [new SelectedScriptStub('s1'), new SelectedScriptStub('s2')];
-      new UserSelectionTestRunner()
-        .withSelectedScripts(scripts)
-        .withCategory(categoryId, scripts.map((s) => s.script))
-      // act
-        .run((sut) => {
-          sut.removeAllInCategory(categoryId);
-        })
-      // assert
-        .expectTotalFiredEvents(1)
-        .expectFinalScripts([]);
-    });
-    describe('removes existing when some exists', () => {
-      // arrange
-      const categoryId = 55;
-      const existing = [new ScriptStub('s1'), new ScriptStub('s2')];
-      const notExisting = [new ScriptStub('s3'), new ScriptStub('s4')];
-      new UserSelectionTestRunner()
-        .withSelectedScripts(existing.map((script) => new SelectedScript(script, false)))
-        .withCategory(categoryId, [...existing, ...notExisting])
-      // act
-        .run((sut) => {
-          sut.removeAllInCategory(categoryId);
-        })
-      // assert
-        .expectTotalFiredEvents(1)
-        .expectFinalScripts([]);
-    });
-  });
-  describe('addOrUpdateAllInCategory', () => {
-    describe('when all already exists', () => {
-      describe('does nothing if nothing is changed', () => {
-        // arrange
-        const categoryId = 55;
-        const existingScripts = [
-          new SelectedScriptStub('s1', false),
-          new SelectedScriptStub('s2', false),
-        ];
-        new UserSelectionTestRunner()
-          .withSelectedScripts(existingScripts)
-          .withCategory(categoryId, existingScripts.map((s) => s.script))
-        // act
-          .run((sut) => {
-            sut.addOrUpdateAllInCategory(categoryId);
-          })
-        // assert
-          .expectTotalFiredEvents(0)
-          .expectFinalScripts(existingScripts);
-      });
-      describe('changes revert status of all', () => {
-        // arrange
-        const newStatus = false;
-        const scripts = [
-          new SelectedScriptStub('e1', !newStatus),
-          new SelectedScriptStub('e2', !newStatus),
-          new SelectedScriptStub('e3', newStatus),
-        ];
-        const expectedScripts = scripts.map((s) => new SelectedScript(s.script, newStatus));
-        const categoryId = 31;
-        new UserSelectionTestRunner()
-          .withSelectedScripts(scripts)
-          .withCategory(categoryId, scripts.map((s) => s.script))
-        // act
-          .run((sut) => {
-            sut.addOrUpdateAllInCategory(categoryId, newStatus);
-          })
-        // assert
-          .expectTotalFiredEvents(1)
-          .expectFinalScripts(expectedScripts)
-          .expectFinalScriptsInEvent(0, expectedScripts);
-      });
-    });
-    describe('when nothing exists; adds all with given revert status', () => {
-      const revertStatuses = [true, false];
-      for (const revertStatus of revertStatuses) {
-        describe(`when revert status is ${revertStatus}`, () => {
-          // arrange
-          const categoryId = 1;
-          const scripts = [
-            new SelectedScriptStub('s1', !revertStatus),
-            new SelectedScriptStub('s2', !revertStatus),
-          ];
-          const expected = scripts.map((s) => new SelectedScript(s.script, revertStatus));
-          new UserSelectionTestRunner()
-            .withSelectedScripts([])
-            .withCategory(categoryId, scripts.map((s) => s.script))
-          // act
-            .run((sut) => {
-              sut.addOrUpdateAllInCategory(categoryId, revertStatus);
-            })
-          // assert
-            .expectTotalFiredEvents(1)
-            .expectFinalScripts(expected)
-            .expectFinalScriptsInEvent(0, expected);
-        });
-      }
-    });
-    describe('when some exists; changes revert status of all', () => {
-      // arrange
-      const newStatus = true;
-      const existing = [
-        new SelectedScriptStub('e1', true),
-        new SelectedScriptStub('e2', false),
-      ];
-      const notExisting = [
-        new SelectedScriptStub('n3', true),
-        new SelectedScriptStub('n4', false),
-      ];
-      const allScripts = [...existing, ...notExisting];
-      const expectedScripts = allScripts.map((s) => new SelectedScript(s.script, newStatus));
-      const categoryId = 77;
-      new UserSelectionTestRunner()
-        .withSelectedScripts(existing)
-        .withCategory(categoryId, allScripts.map((s) => s.script))
-      // act
-        .run((sut) => {
-          sut.addOrUpdateAllInCategory(categoryId, newStatus);
-        })
-      // assert
-        .expectTotalFiredEvents(1)
-        .expectFinalScripts(expectedScripts)
-        .expectFinalScriptsInEvent(0, expectedScripts);
-    });
-  });
-  describe('isSelected', () => {
-    it('returns false when not selected', () => {
-      // arrange
-      const selectedScript = new ScriptStub('selected');
-      const notSelectedScript = new ScriptStub('not selected');
-      const collection = new CategoryCollectionStub()
-        .withAction(new CategoryStub(1)
-          .withScripts(selectedScript, notSelectedScript));
-      const sut = new UserSelection(collection, [new SelectedScript(selectedScript, false)]);
-      // act
-      const actual = sut.isSelected(notSelectedScript.id);
-      // assert
-      expect(actual).to.equal(false);
-    });
-    it('returns true when selected', () => {
-      // arrange
-      const selectedScript = new ScriptStub('selected');
-      const notSelectedScript = new ScriptStub('not selected');
-      const collection = new CategoryCollectionStub()
-        .withAction(new CategoryStub(1)
-          .withScripts(selectedScript, notSelectedScript));
-      const sut = new UserSelection(collection, [new SelectedScript(selectedScript, false)]);
-      // act
-      const actual = sut.isSelected(selectedScript.id);
-      // assert
-      expect(actual).to.equal(true);
-    });
-  });
-  describe('category state', () => {
-    describe('when no scripts are selected', () => {
-      // arrange
-      const category = new CategoryStub(1)
-        .withScriptIds('non-selected-script-1', 'non-selected-script-2');
-      const collection = new CategoryCollectionStub().withAction(category);
-      const sut = new UserSelection(collection, []);
-      it('areAllSelected returns false', () => {
-        // act
-        const actual = sut.areAllSelected(category);
-        // assert
-        expect(actual).to.equal(false);
-      });
-      it('isAnySelected returns false', () => {
-        // act
-        const actual = sut.isAnySelected(category);
-        // assert
-        expect(actual).to.equal(false);
-      });
-    });
-    describe('when no subscript exists in selected scripts', () => {
-      // arrange
-      const category = new CategoryStub(1)
-        .withScriptIds('non-selected-script-1', 'non-selected-script-2');
-      const selectedScript = new ScriptStub('selected');
-      const collection = new CategoryCollectionStub()
-        .withAction(category)
-        .withAction(new CategoryStub(22).withScript(selectedScript));
-      const sut = new UserSelection(collection, [new SelectedScript(selectedScript, false)]);
-      it('areAllSelected returns false', () => {
-        // act
-        const actual = sut.areAllSelected(category);
-        // assert
-        expect(actual).to.equal(false);
-      });
-      it('isAnySelected returns false', () => {
-        // act
-        const actual = sut.isAnySelected(category);
-        // assert
-        expect(actual).to.equal(false);
-      });
-    });
-    describe('when one of the scripts are selected', () => {
-      // arrange
-      const selectedScript = new ScriptStub('selected');
-      const category = new CategoryStub(1)
-        .withScriptIds('non-selected-script-1', 'non-selected-script-2')
-        .withCategory(new CategoryStub(12).withScript(selectedScript));
-      const collection = new CategoryCollectionStub().withAction(category);
-      const sut = new UserSelection(collection, [new SelectedScript(selectedScript, false)]);
-      it('areAllSelected returns false', () => {
-        // act
-        const actual = sut.areAllSelected(category);
-        // assert
-        expect(actual).to.equal(false);
-      });
-      it('isAnySelected returns true', () => {
-        // act
-        const actual = sut.isAnySelected(category);
-        // assert
-        expect(actual).to.equal(true);
-      });
-    });
-    describe('when all scripts are selected', () => {
-      // arrange
-      const firstSelectedScript = new ScriptStub('selected1');
-      const secondSelectedScript = new ScriptStub('selected2');
-      const category = new CategoryStub(1)
-        .withScript(firstSelectedScript)
-        .withCategory(new CategoryStub(12).withScript(secondSelectedScript));
-      const collection = new CategoryCollectionStub().withAction(category);
-      const selectedScripts = [firstSelectedScript, secondSelectedScript]
-        .map((s) => new SelectedScript(s, false));
-      const sut = new UserSelection(collection, selectedScripts);
-      it('areAllSelected returns true', () => {
-        // act
-        const actual = sut.areAllSelected(category);
-        // assert
-        expect(actual).to.equal(true);
-      });
-      it('isAnySelected returns true', () => {
-        // act
-        const actual = sut.isAnySelected(category);
-        // assert
-        expect(actual).to.equal(true);
-      });
-    });
-  });
-});
diff --git a/tests/unit/application/Context/State/Selection/UserSelectionFacade.spec.ts b/tests/unit/application/Context/State/Selection/UserSelectionFacade.spec.ts
new file mode 100644
index 00000000..86f965fb
--- /dev/null
+++ b/tests/unit/application/Context/State/Selection/UserSelectionFacade.spec.ts
@@ -0,0 +1,133 @@
+import { describe, it } from 'vitest';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
+import { UserSelectionFacade } from '@/application/Context/State/Selection/UserSelectionFacade';
+import { ICategoryCollection } from '@/domain/ICategoryCollection';
+import { CategoryCollectionStub } from '@tests/unit/shared/Stubs/CategoryCollectionStub';
+import type { ScriptsFactory, CategoriesFactory } from '@/application/Context/State/Selection/UserSelectionFacade';
+import { ScriptSelectionStub } from '@tests/unit/shared/Stubs/ScriptSelectionStub';
+import { CategorySelectionStub } from '@tests/unit/shared/Stubs/CategorySelectionStub';
+import { expectExists } from '@tests/shared/Assertions/ExpectExists';
+import { SelectedScriptStub } from '@tests/unit/shared/Stubs/SelectedScriptStub';
+import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
+import { ScriptSelection } from '@/application/Context/State/Selection/Script/ScriptSelection';
+
+describe('UserSelectionFacade', () => {
+  describe('ctor', () => {
+    describe('scripts', () => {
+      it('constructs with expected collection', () => {
+        // arrange
+        const expectedCollection = new CategoryCollectionStub();
+        let actualCollection: ICategoryCollection | undefined;
+        const factoryMock: ScriptsFactory = (collection) => {
+          actualCollection = collection;
+          return new ScriptSelectionStub();
+        };
+        const builder = new UserSelectionFacadeBuilder()
+          .withCollection(expectedCollection)
+          .withScriptsFactory(factoryMock);
+        // act
+        builder.construct();
+        // assert
+        expectExists(actualCollection);
+        expect(actualCollection).to.equal(expectedCollection);
+      });
+      it('constructs with expected selected scripts', () => {
+        // arrange
+        const expectedScripts: readonly SelectedScript[] = [
+          new SelectedScriptStub(new ScriptStub('1')),
+        ];
+        let actualScripts: readonly SelectedScript[] | undefined;
+        const factoryMock: ScriptsFactory = (_, scripts) => {
+          actualScripts = scripts;
+          return new ScriptSelectionStub();
+        };
+        const builder = new UserSelectionFacadeBuilder()
+          .withSelectedScripts(expectedScripts)
+          .withScriptsFactory(factoryMock);
+        // act
+        builder.construct();
+        // assert
+        expectExists(actualScripts);
+        expect(actualScripts).to.equal(expectedScripts);
+      });
+    });
+    describe('categories', () => {
+      it('constructs with expected collection', () => {
+        // arrange
+        const expectedCollection = new CategoryCollectionStub();
+        let actualCollection: ICategoryCollection | undefined;
+        const factoryMock: CategoriesFactory = (_, collection) => {
+          actualCollection = collection;
+          return new CategorySelectionStub();
+        };
+        const builder = new UserSelectionFacadeBuilder()
+          .withCollection(expectedCollection)
+          .withCategoriesFactory(factoryMock);
+        // act
+        builder.construct();
+        // assert
+        expectExists(actualCollection);
+        expect(actualCollection).to.equal(expectedCollection);
+      });
+      it('constructs with expected scripts', () => {
+        // arrange
+        const expectedScriptSelection = new ScriptSelectionStub();
+        let actualScriptsSelection: ScriptSelection | undefined;
+        const categoriesFactoryMock: CategoriesFactory = (selection) => {
+          actualScriptsSelection = selection;
+          return new CategorySelectionStub();
+        };
+        const scriptsFactoryMock: ScriptsFactory = () => {
+          return expectedScriptSelection;
+        };
+        const builder = new UserSelectionFacadeBuilder()
+          .withCategoriesFactory(categoriesFactoryMock)
+          .withScriptsFactory(scriptsFactoryMock);
+        // act
+        builder.construct();
+        // assert
+        expectExists(actualScriptsSelection);
+        expect(actualScriptsSelection).to.equal(expectedScriptSelection);
+      });
+    });
+  });
+});
+
+class UserSelectionFacadeBuilder {
+  private collection: ICategoryCollection = new CategoryCollectionStub();
+
+  private selectedScripts: readonly SelectedScript[] = [];
+
+  private scriptsFactory: ScriptsFactory = () => new ScriptSelectionStub();
+
+  private categoriesFactory: CategoriesFactory = () => new CategorySelectionStub();
+
+  public withCollection(collection: ICategoryCollection): this {
+    this.collection = collection;
+    return this;
+  }
+
+  public withSelectedScripts(selectedScripts: readonly SelectedScript[]): this {
+    this.selectedScripts = selectedScripts;
+    return this;
+  }
+
+  public withScriptsFactory(scriptsFactory: ScriptsFactory): this {
+    this.scriptsFactory = scriptsFactory;
+    return this;
+  }
+
+  public withCategoriesFactory(categoriesFactory: CategoriesFactory): this {
+    this.categoriesFactory = categoriesFactory;
+    return this;
+  }
+
+  public construct(): UserSelectionFacade {
+    return new UserSelectionFacade(
+      this.collection,
+      this.selectedScripts,
+      this.scriptsFactory,
+      this.categoriesFactory,
+    );
+  }
+}
diff --git a/tests/unit/application/Context/State/Selection/UserSelectionTestRunner.ts b/tests/unit/application/Context/State/Selection/UserSelectionTestRunner.ts
deleted file mode 100644
index 75563248..00000000
--- a/tests/unit/application/Context/State/Selection/UserSelectionTestRunner.ts
+++ /dev/null
@@ -1,88 +0,0 @@
-import { it, expect } from 'vitest';
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
-import { CategoryCollectionStub } from '@tests/unit/shared/Stubs/CategoryCollectionStub';
-import { CategoryStub } from '@tests/unit/shared/Stubs/CategoryStub';
-import { UserSelection } from '@/application/Context/State/Selection/UserSelection';
-import { IScript } from '@/domain/IScript';
-
-export class UserSelectionTestRunner {
-  private readonly collection = new CategoryCollectionStub();
-
-  private existingScripts: readonly SelectedScript[] = [];
-
-  private events: Array<readonly SelectedScript[]> = [];
-
-  private sut: UserSelection;
-
-  public withCategory(categoryId: number, scripts: readonly IScript[]) {
-    const category = new CategoryStub(categoryId)
-      .withScripts(...scripts);
-    this.collection
-      .withAction(category);
-    return this;
-  }
-
-  public withSelectedScripts(existingScripts: readonly SelectedScript[]) {
-    this.existingScripts = existingScripts;
-    return this;
-  }
-
-  public run(runner?: (sut: UserSelection) => void) {
-    this.sut = this.createSut();
-    if (runner) {
-      runner(this.sut);
-    }
-    return this;
-  }
-
-  public expectTotalFiredEvents(amount: number) {
-    const testName = amount === 0 ? 'does not fire changed event' : `fires changed event ${amount} times`;
-    it(testName, () => {
-      expect(this.events).to.have.lengthOf(amount);
-    });
-    return this;
-  }
-
-  public expectFinalScripts(finalScripts: readonly SelectedScript[]) {
-    expectSameScripts(finalScripts, this.sut.selectedScripts);
-    return this;
-  }
-
-  public expectFinalScriptsInEvent(eventIndex: number, finalScripts: readonly SelectedScript[]) {
-    expectSameScripts(this.events[eventIndex], finalScripts);
-    return this;
-  }
-
-  private createSut(): UserSelection {
-    const sut = new UserSelection(this.collection, this.existingScripts);
-    sut.changed.on((s) => this.events.push(s));
-    return sut;
-  }
-}
-
-function expectSameScripts(actual: readonly SelectedScript[], expected: readonly SelectedScript[]) {
-  it('has same expected scripts', () => {
-    const existingScriptIds = expected.map((script) => script.id).sort();
-    const expectedScriptIds = actual.map((script) => script.id).sort();
-    expect(existingScriptIds).to.deep.equal(expectedScriptIds);
-  });
-  it('has expected revert state', () => {
-    const scriptsWithDifferentStatus = actual
-      .filter((script) => {
-        const other = expected.find((existing) => existing.id === script.id);
-        if (!other) {
-          throw new Error(`Script "${script.id}" does not exist in expected scripts: ${JSON.stringify(expected, null, '\t')}`);
-        }
-        return script.revert !== other.revert;
-      });
-    expect(scriptsWithDifferentStatus).to.have.lengthOf(
-      0,
-      `Scripts with different statuses:\n${
-        scriptsWithDifferentStatus
-          .map((s) => `[id: ${s.id}, actual status: ${s.revert}, `
-            + `expected status: ${expected.find((existing) => existing.id === s.id)?.revert ?? 'unknown'}]`)
-          .join(' , ')
-      }`,
-    );
-  });
-}
diff --git a/tests/unit/presentation/components/Scripts/Menu/Selector/SelectionStateTestScenario.ts b/tests/unit/presentation/components/Scripts/Menu/Selector/SelectionStateTestScenario.ts
index 616585d5..3218f260 100644
--- a/tests/unit/presentation/components/Scripts/Menu/Selector/SelectionStateTestScenario.ts
+++ b/tests/unit/presentation/components/Scripts/Menu/Selector/SelectionStateTestScenario.ts
@@ -1,7 +1,10 @@
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
 import { RecommendationLevel } from '@/domain/RecommendationLevel';
 import { CategoryCollectionStateStub } from '@tests/unit/shared/Stubs/CategoryCollectionStateStub';
+import { ScriptSelectionStub } from '@tests/unit/shared/Stubs/ScriptSelectionStub';
 import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
+import { SelectedScriptStub } from '@tests/unit/shared/Stubs/SelectedScriptStub';
+import { UserSelectionStub } from '@tests/unit/shared/Stubs/UserSelectionStub';
 
 export class SelectionStateTestScenario {
   public readonly all: readonly SelectedScript[];
@@ -28,13 +31,21 @@ export class SelectionStateTestScenario {
     this.all = [...this.allStandard, ...this.allStrict, ...this.allUnrecommended];
   }
 
-  public generateState(selectedScripts: readonly SelectedScript[]) {
+  public generateState(selectedScripts: readonly SelectedScript[] = []) {
     const allScripts = this.all.map((s) => s.script);
-    return new CategoryCollectionStateStub(allScripts)
+    const scriptSelection = new ScriptSelectionStub()
       .withSelectedScripts(selectedScripts);
+    const categoryCollectionState = new CategoryCollectionStateStub(allScripts)
+      .withSelection(new UserSelectionStub().withScripts(scriptSelection));
+    return {
+      scriptsStub: scriptSelection,
+      stateStub: categoryCollectionState,
+    };
   }
 }
 
-function createSelectedScripts(level?: RecommendationLevel, ...ids: string[]) {
-  return ids.map((id) => new SelectedScript(new ScriptStub(id).withLevel(level), false));
+function createSelectedScripts(level?: RecommendationLevel, ...ids: string[]): SelectedScript[] {
+  return ids.map((id) => new SelectedScriptStub(
+    new ScriptStub(id).withLevel(level),
+  ).withRevert(false));
 }
diff --git a/tests/unit/presentation/components/Scripts/Menu/Selector/SelectionTypeHandler.spec.ts b/tests/unit/presentation/components/Scripts/Menu/Selector/SelectionTypeHandler.spec.ts
index 7ff70abc..97e29f1f 100644
--- a/tests/unit/presentation/components/Scripts/Menu/Selector/SelectionTypeHandler.spec.ts
+++ b/tests/unit/presentation/components/Scripts/Menu/Selector/SelectionTypeHandler.spec.ts
@@ -3,10 +3,14 @@ import {
   SelectionCheckContext, SelectionMutationContext, SelectionType,
   getCurrentSelectionType, setCurrentSelectionType,
 } from '@/presentation/components/Scripts/Menu/Selector/SelectionTypeHandler';
-import { scrambledEqual } from '@/application/Common/Array';
 import { RecommendationLevel } from '@/domain/RecommendationLevel';
 import { ICategoryCollectionState } from '@/application/Context/State/ICategoryCollectionState';
 import { EnumRangeTestRunner } from '@tests/unit/application/Common/EnumRangeTestRunner';
+import { ScriptSelection } from '@/application/Context/State/Selection/Script/ScriptSelection';
+import { MethodCall } from '@tests/unit/shared/Stubs/StubWithObservableMethodCalls';
+import { expectExists } from '@tests/shared/Assertions/ExpectExists';
+import { scrambledEqual } from '@/application/Common/Array';
+import { IScript } from '@/domain/IScript';
 import { SelectionStateTestScenario } from './SelectionStateTestScenario';
 
 describe('SelectionTypeHandler', () => {
@@ -14,11 +18,11 @@ describe('SelectionTypeHandler', () => {
     describe('throws with invalid type', () => {
       // arrange
       const scenario = new SelectionStateTestScenario();
-      const state = scenario.generateState([]);
+      const { stateStub } = scenario.generateState([]);
       // act
       const act = (type: SelectionType) => setCurrentSelectionType(
         type,
-        createMutationContext(state),
+        createMutationContext(stateStub),
       );
       // assert
       new EnumRangeTestRunner(act)
@@ -28,44 +32,64 @@ describe('SelectionTypeHandler', () => {
     describe('select types as expected', () => {
       // arrange
       const scenario = new SelectionStateTestScenario();
-      const initialScriptsCases = [{
-        name: 'when nothing is selected',
-        initialScripts: [],
-      }, {
-        name: 'when some scripts are selected',
-        initialScripts: [...scenario.allStandard, ...scenario.someStrict],
-      }, {
-        name: 'when all scripts are selected',
-        initialScripts: scenario.all,
-      }];
-      for (const initialScriptsCase of initialScriptsCases) {
-        describe(initialScriptsCase.name, () => {
-          const state = scenario.generateState(initialScriptsCase.initialScripts);
-          const typeExpectations = [{
-            input: SelectionType.None,
-            output: [],
-          }, {
-            input: SelectionType.Standard,
-            output: scenario.allStandard,
-          }, {
-            input: SelectionType.Strict,
-            output: [...scenario.allStandard, ...scenario.allStrict],
-          }, {
-            input: SelectionType.All,
-            output: scenario.all,
-          }];
-          for (const expectation of typeExpectations) {
-            // act
-            it(`${SelectionType[expectation.input]} returns as expected`, () => {
-              setCurrentSelectionType(expectation.input, createMutationContext(state));
-              // assert
-              const actual = state.selection.selectedScripts;
-              const expected = expectation.output;
-              expect(scrambledEqual(actual, expected));
-            });
+      const testScenarios: ReadonlyArray<{
+        readonly givenType: SelectionType;
+        readonly expectedCall: MethodCall<ScriptSelection>;
+      }> = [
+        {
+          givenType: SelectionType.None,
+          expectedCall: {
+            methodName: 'deselectAll',
+            args: [],
+          },
+        },
+        {
+          givenType: SelectionType.Standard,
+          expectedCall: {
+            methodName: 'selectOnly',
+            args: [
+              scenario.allStandard.map((s) => s.script),
+            ],
+          },
+        },
+        {
+          givenType: SelectionType.Strict,
+          expectedCall: {
+            methodName: 'selectOnly',
+            args: [[
+              ...scenario.allStandard.map((s) => s.script),
+              ...scenario.allStrict.map((s) => s.script),
+            ]],
+          },
+        },
+        {
+          givenType: SelectionType.All,
+          expectedCall: {
+            methodName: 'selectAll',
+            args: [],
+          },
+        },
+      ];
+      testScenarios.forEach(({
+        givenType, expectedCall,
+      }) => {
+        it(`${SelectionType[givenType]} modifies as expected`, () => {
+          const { stateStub, scriptsStub } = scenario.generateState();
+          // act
+          setCurrentSelectionType(givenType, createMutationContext(stateStub));
+          // assert
+          const call = scriptsStub.callHistory.find(
+            (c) => c.methodName === expectedCall.methodName,
+          );
+          expectExists(call);
+          if (expectedCall.args.length > 0) { /** {@link ScriptSelection.selectOnly}. */
+            expect(scrambledEqual(
+              call.args[0] as IScript[],
+              expectedCall.args[0] as IScript[],
+            )).to.equal(true);
           }
         });
-      }
+      });
     });
   });
   describe('getCurrentSelectionType', () => {
@@ -106,9 +130,9 @@ describe('SelectionTypeHandler', () => {
     }];
     for (const testCase of testCases) {
       it(testCase.name, () => {
-        const state = scenario.generateState(testCase.selection);
+        const { stateStub } = scenario.generateState(testCase.selection);
         // act
-        const actual = getCurrentSelectionType(createCheckContext(state));
+        const actual = getCurrentSelectionType(createCheckContext(stateStub));
         // assert
         expect(actual).to.deep.equal(
           testCase.expected,
@@ -130,14 +154,14 @@ describe('SelectionTypeHandler', () => {
 
 function createMutationContext(state: ICategoryCollectionState): SelectionMutationContext {
   return {
-    selection: state.selection,
+    selection: state.selection.scripts,
     collection: state.collection,
   };
 }
 
 function createCheckContext(state: ICategoryCollectionState): SelectionCheckContext {
   return {
-    selection: state.selection,
+    selection: state.selection.scripts,
     collection: state.collection,
   };
 }
diff --git a/tests/unit/presentation/components/Scripts/View/Tree/NodeContent/Reverter/CategoryReverter.spec.ts b/tests/unit/presentation/components/Scripts/View/Tree/NodeContent/Reverter/CategoryReverter.spec.ts
index 336b3196..69122db8 100644
--- a/tests/unit/presentation/components/Scripts/View/Tree/NodeContent/Reverter/CategoryReverter.spec.ts
+++ b/tests/unit/presentation/components/Scripts/View/Tree/NodeContent/Reverter/CategoryReverter.spec.ts
@@ -1,106 +1,101 @@
 import { describe, it, expect } from 'vitest';
 import { CategoryReverter } from '@/presentation/components/Scripts/View/Tree/NodeContent/Reverter/CategoryReverter';
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
-import { UserSelection } from '@/application/Context/State/Selection/UserSelection';
 import { CategoryStub } from '@tests/unit/shared/Stubs/CategoryStub';
 import { CategoryCollectionStub } from '@tests/unit/shared/Stubs/CategoryCollectionStub';
 import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
 import { getCategoryNodeId } from '@/presentation/components/Scripts/View/Tree/TreeViewAdapter/CategoryNodeMetadataConverter';
+import { UserSelectionStub } from '@tests/unit/shared/Stubs/UserSelectionStub';
+import { SelectedScriptStub } from '@tests/unit/shared/Stubs/SelectedScriptStub';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
+import { CategorySelectionStub } from '@tests/unit/shared/Stubs/CategorySelectionStub';
 
 describe('CategoryReverter', () => {
   describe('getState', () => {
     // arrange
     const scripts = [
-      new ScriptStub('revertable').withRevertCode('REM revert me'),
-      new ScriptStub('revertable2').withRevertCode('REM revert me 2'),
+      new ScriptStub('reversible').withRevertCode('REM revert me'),
+      new ScriptStub('reversible2').withRevertCode('REM revert me 2'),
     ];
     const category = new CategoryStub(1).withScripts(...scripts);
     const nodeId = getCategoryNodeId(category);
     const collection = new CategoryCollectionStub().withAction(category);
     const sut = new CategoryReverter(nodeId, collection);
-    const testCases = [
+    const testScenarios: ReadonlyArray<{
+      readonly description: string;
+      readonly selectedScripts: readonly SelectedScript[];
+      readonly expectedState: boolean;
+    }> = [
       {
-        name: 'false when subscripts are not reverted',
-        state: scripts.map((script) => new SelectedScript(script, false)),
-        expected: false,
+        description: 'returns `false` for non-reverted subscripts',
+        selectedScripts: scripts.map(
+          (script) => new SelectedScriptStub(script).withRevert(false),
+        ),
+        expectedState: false,
       },
       {
-        name: 'false when some subscripts are reverted',
-        state: [new SelectedScript(scripts[0], false), new SelectedScript(scripts[0], true)],
-        expected: false,
+        description: 'returns `false` when only some subscripts are reverted',
+        selectedScripts: [
+          new SelectedScriptStub(scripts[0]).withRevert(false),
+          new SelectedScriptStub(scripts[0]).withRevert(true),
+        ],
+        expectedState: false,
       },
       {
-        name: 'false when subscripts are not reverted',
-        state: scripts.map((script) => new SelectedScript(script, true)),
-        expected: true,
+        description: 'returns `true` when all subscripts are reverted',
+        selectedScripts: scripts.map(
+          (script) => new SelectedScriptStub(script).withRevert(true),
+        ),
+        expectedState: true,
       },
     ];
-    for (const testCase of testCases) {
-      it(testCase.name, () => {
+    testScenarios.forEach((
+      { description, selectedScripts, expectedState },
+    ) => {
+      it(description, () => {
         // act
-        const actual = sut.getState(testCase.state);
+        const actual = sut.getState(selectedScripts);
         // assert
-        expect(actual).to.equal(testCase.expected);
+        expect(actual).to.equal(expectedState);
       });
-    }
+    });
   });
   describe('selectWithRevertState', () => {
     // arrange
-    const scripts = [
-      new ScriptStub('revertable').withRevertCode('REM revert me'),
-      new ScriptStub('revertable2').withRevertCode('REM revert me 2'),
+    const allScripts = [
+      new ScriptStub('reversible').withRevertCode('REM revert me'),
+      new ScriptStub('reversible2').withRevertCode('REM revert me 2'),
     ];
-    const category = new CategoryStub(1).withScripts(...scripts);
+    const category = new CategoryStub(1).withScripts(...allScripts);
     const collection = new CategoryCollectionStub().withAction(category);
-    /* eslint-disable object-property-newline */
-    const testCases = [
+    const testScenarios: ReadonlyArray<{
+      readonly description: string;
+      readonly expectedRevert: boolean;
+    }> = [
       {
-        name: 'selects with revert state when not selected',
-        selection: [],
-        revert: true, expectRevert: true,
+        description: 'selects with revert',
+        expectedRevert: true,
       },
       {
-        name: 'selects with non-revert state when not selected',
-        selection: [],
-        revert: false, expectRevert: false,
-      },
-      {
-        name: 'switches when already selected with revert state',
-        selection: scripts.map((script) => new SelectedScript(script, true)),
-        revert: false, expectRevert: false,
-      },
-      {
-        name: 'switches when already selected with not revert state',
-        selection: scripts.map((script) => new SelectedScript(script, false)),
-        revert: true, expectRevert: true,
-      },
-      {
-        name: 'keeps revert state when already selected with revert state',
-        selection: scripts.map((script) => new SelectedScript(script, true)),
-        revert: true, expectRevert: true,
-      },
-      {
-        name: 'keeps revert state deselected when already selected wtih non revert state',
-        selection: scripts.map((script) => new SelectedScript(script, false)),
-        revert: false, expectRevert: false,
+        description: 'selects without revert',
+        expectedRevert: false,
       },
     ];
-    /* eslint-enable object-property-newline */
     const nodeId = getCategoryNodeId(category);
-    for (const testCase of testCases) {
-      it(testCase.name, () => {
-        const selection = new UserSelection(collection, testCase.selection);
+    testScenarios.forEach((
+      { description, expectedRevert },
+    ) => {
+      it(description, () => {
+        const categorySelection = new CategorySelectionStub();
         const sut = new CategoryReverter(nodeId, collection);
+        const revertState = expectedRevert;
         // act
-        sut.selectWithRevertState(testCase.revert, selection);
+        sut.selectWithRevertState(
+          revertState,
+          new UserSelectionStub().withCategories(categorySelection),
+        );
         // assert
-        expect(sut.getState(selection.selectedScripts)).to.equal(testCase.expectRevert);
-        expect(selection.selectedScripts).has.lengthOf(2);
-        expect(selection.selectedScripts[0].id).equal(scripts[0].id);
-        expect(selection.selectedScripts[1].id).equal(scripts[1].id);
-        expect(selection.selectedScripts[0].revert).equal(testCase.expectRevert);
-        expect(selection.selectedScripts[1].revert).equal(testCase.expectRevert);
+        expect(categorySelection.isCategorySelected(category.id, expectedRevert)).to.equal(true);
       });
-    }
+    });
   });
 });
diff --git a/tests/unit/presentation/components/Scripts/View/Tree/NodeContent/Reverter/ScriptReverter.spec.ts b/tests/unit/presentation/components/Scripts/View/Tree/NodeContent/Reverter/ScriptReverter.spec.ts
index 2de0ffbe..dca7751d 100644
--- a/tests/unit/presentation/components/Scripts/View/Tree/NodeContent/Reverter/ScriptReverter.spec.ts
+++ b/tests/unit/presentation/components/Scripts/View/Tree/NodeContent/Reverter/ScriptReverter.spec.ts
@@ -1,90 +1,118 @@
 import { describe, it, expect } from 'vitest';
 import { ScriptReverter } from '@/presentation/components/Scripts/View/Tree/NodeContent/Reverter/ScriptReverter';
-import { UserSelection } from '@/application/Context/State/Selection/UserSelection';
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
-import { CategoryCollectionStub } from '@tests/unit/shared/Stubs/CategoryCollectionStub';
-import { CategoryStub } from '@tests/unit/shared/Stubs/CategoryStub';
 import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
 import { SelectedScriptStub } from '@tests/unit/shared/Stubs/SelectedScriptStub';
 import { getScriptNodeId } from '@/presentation/components/Scripts/View/Tree/TreeViewAdapter/CategoryNodeMetadataConverter';
+import { UserSelectionStub } from '@tests/unit/shared/Stubs/UserSelectionStub';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
+import { ScriptSelectionStub } from '@tests/unit/shared/Stubs/ScriptSelectionStub';
 
 describe('ScriptReverter', () => {
   describe('getState', () => {
-    it('false when script is not selected', () => {
-      // arrange
-      const script = new ScriptStub('id');
-      const nodeId = getScriptNodeId(script);
-      const sut = new ScriptReverter(nodeId);
-      // act
-      const actual = sut.getState([]);
-      // assert
-      expect(actual).to.equal(false);
-    });
-    it('false when script is selected but not reverted', () => {
-      // arrange
-      const scripts = [new SelectedScriptStub('id'), new SelectedScriptStub('dummy')];
-      const nodeId = getScriptNodeId(scripts[0].script);
-      const sut = new ScriptReverter(nodeId);
-      // act
-      const actual = sut.getState(scripts);
-      // assert
-      expect(actual).to.equal(false);
-    });
-    it('true when script is selected and reverted', () => {
-      // arrange
-      const scripts = [new SelectedScriptStub('id', true), new SelectedScriptStub('dummy')];
-      const nodeId = getScriptNodeId(scripts[0].script);
-      const sut = new ScriptReverter(nodeId);
-      // act
-      const actual = sut.getState(scripts);
-      // assert
-      expect(actual).to.equal(true);
+    // arrange
+    const script = new ScriptStub('id');
+    const nodeId = getScriptNodeId(script);
+    const testScenarios: ReadonlyArray<{
+      readonly description: string;
+      readonly selectedScripts: readonly SelectedScript[];
+      readonly expectedState: boolean;
+    }> = [
+      {
+        description: 'returns `false` when script is not selected',
+        selectedScripts: [],
+        expectedState: false,
+      },
+      {
+        description: 'returns `false` when script is selected but not reverted',
+        selectedScripts: [
+          new SelectedScriptStub(script).withRevert(false),
+          new SelectedScriptStub(new ScriptStub('dummy')),
+        ],
+        expectedState: false,
+      },
+      {
+        description: 'returns `true` when script is selected and reverted',
+        selectedScripts: [
+          new SelectedScriptStub(script).withRevert(true),
+          new SelectedScriptStub(new ScriptStub('dummy')),
+        ],
+        expectedState: true,
+      },
+    ];
+    testScenarios.forEach((
+      { description, selectedScripts, expectedState },
+    ) => {
+      it(description, () => {
+        const sut = new ScriptReverter(nodeId);
+        // act
+        const actual = sut.getState(selectedScripts);
+        // assert
+        expect(actual).to.equal(expectedState);
+      });
     });
   });
   describe('selectWithRevertState', () => {
     // arrange
     const script = new ScriptStub('id');
-    const collection = new CategoryCollectionStub()
-      .withAction(new CategoryStub(5).withScript(script));
-    /* eslint-disable object-property-newline */
-    const testCases = [
+    const testScenarios: ReadonlyArray<{
+      readonly description: string;
+      readonly selection: readonly SelectedScript[];
+      readonly expectedRevert: boolean;
+    }> = [
       {
-        name: 'selects with revert state when not selected',
-        selection: [], revert: true, expectRevert: true,
+        description: 'selects as reverted when initially unselected',
+        selection: [],
+        expectedRevert: true,
       },
       {
-        name: 'selects with non-revert state when not selected',
-        selection: [], revert: false, expectRevert: false,
+        description: 'selects as non-reverted when initially unselected',
+        selection: [],
+        expectedRevert: false,
       },
       {
-        name: 'switches when already selected with revert state',
-        selection: [new SelectedScript(script, true)], revert: false, expectRevert: false,
+        description: 'toggles to non-reverted for previously reverted scripts',
+        selection: [
+          new SelectedScriptStub(script).withRevert(true),
+        ],
+        expectedRevert: false,
       },
       {
-        name: 'switches when already selected with not revert state',
-        selection: [new SelectedScript(script, false)], revert: true, expectRevert: true,
+        description: 'toggles to reverted for previously non-reverted scripts',
+        selection: [
+          new SelectedScriptStub(script).withRevert(false),
+        ],
+        expectedRevert: true,
       },
       {
-        name: 'keeps revert state when already selected with revert state',
-        selection: [new SelectedScript(script, true)], revert: true, expectRevert: true,
+        description: 'maintains reverted state for already reverted scripts',
+        selection: [
+          new SelectedScriptStub(script).withRevert(true),
+        ],
+        expectedRevert: true,
       },
       {
-        name: 'keeps revert state deselected when already selected with non revert state',
-        selection: [new SelectedScript(script, false)], revert: false, expectRevert: false,
+        description: 'maintains non-reverted state for already non-reverted scripts',
+        selection: [
+          new SelectedScriptStub(script).withRevert(false),
+        ],
+        expectedRevert: false,
       },
     ];
-    /* eslint-enable object-property-newline */
     const nodeId = getScriptNodeId(script);
-    for (const testCase of testCases) {
-      it(testCase.name, () => {
-        const selection = new UserSelection(collection, testCase.selection);
+    testScenarios.forEach((
+      { description, selection, expectedRevert },
+    ) => {
+      it(description, () => {
+        const scriptSelection = new ScriptSelectionStub()
+          .withSelectedScripts(selection);
+        const userSelection = new UserSelectionStub().withScripts(scriptSelection);
         const sut = new ScriptReverter(nodeId);
+        const revertState = expectedRevert;
         // act
-        sut.selectWithRevertState(testCase.revert, selection);
+        sut.selectWithRevertState(revertState, userSelection);
         // assert
-        expect(selection.isSelected(script.id)).to.equal(true);
-        expect(selection.selectedScripts[0].revert).equal(testCase.expectRevert);
+        expect(scriptSelection.isScriptSelected(script.id, expectedRevert)).to.equal(true);
       });
-    }
+    });
   });
 });
diff --git a/tests/unit/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseCollectionSelectionStateUpdater.spec.ts b/tests/unit/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseCollectionSelectionStateUpdater.spec.ts
index 7d1f02cb..be1a2ad6 100644
--- a/tests/unit/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseCollectionSelectionStateUpdater.spec.ts
+++ b/tests/unit/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseCollectionSelectionStateUpdater.spec.ts
@@ -7,6 +7,7 @@ import { TreeNodeCheckState } from '@/presentation/components/Scripts/View/Tree/
 import { UserSelectionStub } from '@tests/unit/shared/Stubs/UserSelectionStub';
 import { TreeNodeStateChangedEmittedEventStub } from '@tests/unit/shared/Stubs/TreeNodeStateChangedEmittedEventStub';
 import { UseUserSelectionStateStub } from '@tests/unit/shared/Stubs/UseUserSelectionStateStub';
+import { ScriptSelectionStub } from '@tests/unit/shared/Stubs/ScriptSelectionStub';
 
 describe('useCollectionSelectionStateUpdater', () => {
   describe('updateNodeSelection', () => {
@@ -56,9 +57,12 @@ describe('useCollectionSelectionStateUpdater', () => {
       it('adds to selection if not already selected', () => {
         // arrange
         const { returnObject, useSelectionStateStub } = runHook();
-        const selectionStub = new UserSelectionStub([]);
-        selectionStub.isSelected = () => false;
-        useSelectionStateStub.withUserSelection(selectionStub);
+        const isScriptInitiallySelected = false;
+        const scriptSelectionStub = new ScriptSelectionStub()
+          .withIsSelectedResult(isScriptInitiallySelected);
+        useSelectionStateStub.withUserSelection(
+          new UserSelectionStub().withScripts(scriptSelectionStub),
+        );
         const node = createTreeNodeStub({
           isBranch: false,
           currentState: TreeNodeCheckState.Checked,
@@ -73,14 +77,17 @@ describe('useCollectionSelectionStateUpdater', () => {
         returnObject.updateNodeSelection(mockEvent);
         // assert
         expect(useSelectionStateStub.isSelectionModified()).to.equal(true);
-        expect(selectionStub.isScriptAdded(node.id)).to.equal(true);
+        expect(scriptSelectionStub.isScriptSelected(node.id, false)).to.equal(true);
       });
       it('does nothing if already selected', () => {
         // arrange
         const { returnObject, useSelectionStateStub } = runHook();
-        const selectionStub = new UserSelectionStub([]);
-        selectionStub.isSelected = () => true;
-        useSelectionStateStub.withUserSelection(selectionStub);
+        const isScriptInitiallySelected = true;
+        const scriptSelectionStub = new ScriptSelectionStub()
+          .withIsSelectedResult(isScriptInitiallySelected);
+        useSelectionStateStub.withUserSelection(
+          new UserSelectionStub().withScripts(scriptSelectionStub),
+        );
         const mockEvent = new TreeNodeStateChangedEmittedEventStub()
           .withNode(
             createTreeNodeStub({
@@ -102,9 +109,12 @@ describe('useCollectionSelectionStateUpdater', () => {
       it('removes from selection if already selected', () => {
         // arrange
         const { returnObject, useSelectionStateStub } = runHook();
-        const selectionStub = new UserSelectionStub([]);
-        selectionStub.isSelected = () => true;
-        useSelectionStateStub.withUserSelection(selectionStub);
+        const isScriptInitiallySelected = true;
+        const scriptSelectionStub = new ScriptSelectionStub()
+          .withIsSelectedResult(isScriptInitiallySelected);
+        useSelectionStateStub.withUserSelection(
+          new UserSelectionStub().withScripts(scriptSelectionStub),
+        );
         const node = createTreeNodeStub({
           isBranch: false,
           currentState: TreeNodeCheckState.Unchecked,
@@ -119,14 +129,17 @@ describe('useCollectionSelectionStateUpdater', () => {
         returnObject.updateNodeSelection(mockEvent);
         // assert
         expect(useSelectionStateStub.isSelectionModified()).to.equal(true);
-        expect(selectionStub.isScriptRemoved(node.id)).to.equal(true);
+        expect(scriptSelectionStub.isScriptDeselected(node.id)).to.equal(true);
       });
       it('does nothing if not already selected', () => {
         // arrange
         const { returnObject, useSelectionStateStub } = runHook();
-        const selectionStub = new UserSelectionStub([]);
-        selectionStub.isSelected = () => false;
-        useSelectionStateStub.withUserSelection(selectionStub);
+        const isScriptInitiallySelected = false;
+        const scriptSelectionStub = new ScriptSelectionStub()
+          .withIsSelectedResult(isScriptInitiallySelected);
+        useSelectionStateStub.withUserSelection(
+          new UserSelectionStub().withScripts(scriptSelectionStub),
+        );
         const mockEvent = new TreeNodeStateChangedEmittedEventStub()
           .withNode(
             createTreeNodeStub({
diff --git a/tests/unit/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseSelectedScriptNodeIds.spec.ts b/tests/unit/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseSelectedScriptNodeIds.spec.ts
index f8e483b4..bac33b49 100644
--- a/tests/unit/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseSelectedScriptNodeIds.spec.ts
+++ b/tests/unit/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseSelectedScriptNodeIds.spec.ts
@@ -4,6 +4,7 @@ import { SelectedScriptStub } from '@tests/unit/shared/Stubs/SelectedScriptStub'
 import { getScriptNodeId } from '@/presentation/components/Scripts/View/Tree/TreeViewAdapter/CategoryNodeMetadataConverter';
 import { IScript } from '@/domain/IScript';
 import { UseUserSelectionStateStub } from '@tests/unit/shared/Stubs/UseUserSelectionStateStub';
+import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
 
 describe('useSelectedScriptNodeIds', () => {
   it('returns an empty array when no scripts are selected', () => {
@@ -19,8 +20,8 @@ describe('useSelectedScriptNodeIds', () => {
     it('immediately', () => {
       // arrange
       const selectedScripts = [
-        new SelectedScriptStub('id-1'),
-        new SelectedScriptStub('id-2'),
+        new SelectedScriptStub(new ScriptStub('id-1')),
+        new SelectedScriptStub(new ScriptStub('id-2')),
       ];
       const parsedNodeIds = new Map<IScript, string>([
         [selectedScripts[0].script, 'expected-id-1'],
@@ -43,8 +44,8 @@ describe('useSelectedScriptNodeIds', () => {
       // arrange
       const initialScripts = [];
       const changedScripts = [
-        new SelectedScriptStub('id-1'),
-        new SelectedScriptStub('id-2'),
+        new SelectedScriptStub(new ScriptStub('id-1')),
+        new SelectedScriptStub(new ScriptStub('id-2')),
       ];
       const parsedNodeIds = new Map<IScript, string>([
         [changedScripts[0].script, 'expected-id-1'],
diff --git a/tests/unit/presentation/components/Shared/Hooks/UseUserSelectionState.spec.ts b/tests/unit/presentation/components/Shared/Hooks/UseUserSelectionState.spec.ts
index 3323b54f..d6f20296 100644
--- a/tests/unit/presentation/components/Shared/Hooks/UseUserSelectionState.spec.ts
+++ b/tests/unit/presentation/components/Shared/Hooks/UseUserSelectionState.spec.ts
@@ -1,19 +1,20 @@
 import { describe, it, expect } from 'vitest';
 import { nextTick, watch } from 'vue';
 import { SelectionModifier, useUserSelectionState } from '@/presentation/components/Shared/Hooks/UseUserSelectionState';
+import { UserSelection } from '@/application/Context/State/Selection/UserSelection';
 import { UseCollectionStateStub } from '@tests/unit/shared/Stubs/UseCollectionStateStub';
 import { UseAutoUnsubscribedEventsStub } from '@tests/unit/shared/Stubs/UseAutoUnsubscribedEventsStub';
 import { UserSelectionStub } from '@tests/unit/shared/Stubs/UserSelectionStub';
 import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
 import { CategoryCollectionStateStub } from '@tests/unit/shared/Stubs/CategoryCollectionStateStub';
-import { IUserSelection } from '@/application/Context/State/Selection/IUserSelection';
 import { SelectedScriptStub } from '@tests/unit/shared/Stubs/SelectedScriptStub';
+import { ScriptSelectionStub } from '@tests/unit/shared/Stubs/ScriptSelectionStub';
 
 describe('useUserSelectionState', () => {
   describe('currentSelection', () => {
     it('initializes with correct selection', () => {
       // arrange
-      const expectedSelection = new UserSelectionStub([new ScriptStub('initialSelectedScript')]);
+      const expectedSelection = new UserSelectionStub();
       const collectionStateStub = new UseCollectionStateStub()
         .withState(new CategoryCollectionStateStub().withSelection(expectedSelection));
       // act
@@ -27,8 +28,8 @@ describe('useUserSelectionState', () => {
     describe('once collection state is changed', () => {
       it('updated', () => {
         // arrange
-        const initialSelection = new UserSelectionStub([new ScriptStub('initialSelectedScript')]);
-        const changedSelection = new UserSelectionStub([new ScriptStub('changedSelectedScript')]);
+        const initialSelection = new UserSelectionStub();
+        const changedSelection = new UserSelectionStub();
         const collectionStateStub = new UseCollectionStateStub()
           .withState(new CategoryCollectionStateStub().withSelection(initialSelection));
         const { returnObject } = runHook({
@@ -45,8 +46,9 @@ describe('useUserSelectionState', () => {
       });
       it('not updated when old state changes', async () => {
         // arrange
-        const oldSelectionState = new UserSelectionStub([new ScriptStub('inOldState')]);
-        const newSelectionState = new UserSelectionStub([new ScriptStub('inNewState')]);
+        const oldScriptSelection = new ScriptSelectionStub();
+        const oldSelectionState = new UserSelectionStub().withScripts(oldScriptSelection);
+        const newSelectionState = new UserSelectionStub();
         const collectionStateStub = new UseCollectionStateStub()
           .withState(new CategoryCollectionStateStub().withSelection(oldSelectionState));
         const { returnObject } = runHook({
@@ -61,7 +63,9 @@ describe('useUserSelectionState', () => {
           totalUpdates++;
         });
         // act
-        oldSelectionState.triggerSelectionChangedEvent([new SelectedScriptStub('newInOldState')]);
+        oldScriptSelection.triggerSelectionChangedEvent([
+          new SelectedScriptStub(new ScriptStub('newInOldState')),
+        ]);
         await nextTick();
         // assert
         expect(totalUpdates).to.equal(0);
@@ -69,8 +73,8 @@ describe('useUserSelectionState', () => {
       describe('triggers change', () => {
         it('with new selection reference', async () => {
           // arrange
-          const oldSelection = new UserSelectionStub([]);
-          const newSelection = new UserSelectionStub([]);
+          const oldSelection = new UserSelectionStub();
+          const newSelection = new UserSelectionStub();
           const initialCollectionState = new CategoryCollectionStateStub()
             .withSelection(oldSelection);
           const changedCollectionState = new CategoryCollectionStateStub()
@@ -93,7 +97,7 @@ describe('useUserSelectionState', () => {
         });
         it('with the same selection reference', async () => {
           // arrange
-          const userSelection = new UserSelectionStub([new ScriptStub('sameScriptInSameReference')]);
+          const userSelection = new UserSelectionStub();
           const initialCollectionState = new CategoryCollectionStateStub()
             .withSelection(userSelection);
           const changedCollectionState = new CategoryCollectionStateStub()
@@ -119,26 +123,38 @@ describe('useUserSelectionState', () => {
     describe('once selection state is changed', () => {
       it('updated with same collection state', async () => {
         // arrange
-        const initialScripts = [new ScriptStub('initialSelectedScript')];
-        const changedScripts = [new SelectedScriptStub('changedSelectedScript')];
-        const selectionState = new UserSelectionStub(initialScripts);
-        const collectionState = new CategoryCollectionStateStub().withSelection(selectionState);
+        const initialScripts = [
+          new SelectedScriptStub(new ScriptStub('initialSelectedScript')),
+        ];
+        const changedScripts = [
+          new SelectedScriptStub(new ScriptStub('changedSelectedScript')),
+        ];
+        const scriptSelectionStub = new ScriptSelectionStub()
+          .withSelectedScripts(initialScripts);
+        const expectedSelectionState = new UserSelectionStub().withScripts(scriptSelectionStub);
+        const collectionState = new CategoryCollectionStateStub()
+          .withSelection(expectedSelectionState);
         const collectionStateStub = new UseCollectionStateStub().withState(collectionState);
         const { returnObject } = runHook({
           useCollectionState: collectionStateStub,
         });
         // act
-        selectionState.triggerSelectionChangedEvent(changedScripts);
+        scriptSelectionStub.triggerSelectionChangedEvent(changedScripts);
         await nextTick();
         // assert
         const actualSelection = returnObject.currentSelection.value;
-        expect(actualSelection).to.equal(selectionState);
+        expect(actualSelection).to.equal(expectedSelectionState);
       });
       it('updated once collection state is changed', async () => {
         // arrange
-        const changedScripts = [new SelectedScriptStub('changedSelectedScript')];
-        const newSelectionState = new UserSelectionStub([new ScriptStub('initialSelectedScriptInNewCollection')]);
-        const initialCollectionState = new CategoryCollectionStateStub().withSelectedScripts([new SelectedScriptStub('initialSelectedScriptInInitialCollection')]);
+        const changedScripts = [
+          new SelectedScriptStub(new ScriptStub('changedSelectedScript')),
+        ];
+        const scriptSelectionStub = new ScriptSelectionStub();
+        const newSelectionState = new UserSelectionStub().withScripts(scriptSelectionStub);
+        const initialCollectionState = new CategoryCollectionStateStub().withSelectedScripts([
+          new SelectedScriptStub(new ScriptStub('initialSelectedScriptInInitialCollection')),
+        ]);
         const collectionStateStub = new UseCollectionStateStub().withState(initialCollectionState);
         const { returnObject } = runHook({ useCollectionState: collectionStateStub });
         // act
@@ -146,7 +162,7 @@ describe('useUserSelectionState', () => {
           newState: new CategoryCollectionStateStub().withSelection(newSelectionState),
           immediateOnly: false,
         });
-        newSelectionState.triggerSelectionChangedEvent(changedScripts);
+        scriptSelectionStub.triggerSelectionChangedEvent(changedScripts);
         // assert
         const actualSelection = returnObject.currentSelection.value;
         expect(actualSelection).to.equal(newSelectionState);
@@ -156,17 +172,19 @@ describe('useUserSelectionState', () => {
           // arrange
           const oldSelectedScriptsArrayReference = [];
           const newSelectedScriptsArrayReference = [];
-          const userSelection = new UserSelectionStub(oldSelectedScriptsArrayReference)
+          const scriptSelectionStub = new ScriptSelectionStub()
             .withSelectedScripts(oldSelectedScriptsArrayReference);
           const collectionStateStub = new UseCollectionStateStub()
-            .withState(new CategoryCollectionStateStub().withSelection(userSelection));
+            .withState(new CategoryCollectionStateStub().withSelection(
+              new UserSelectionStub().withScripts(scriptSelectionStub),
+            ));
           const { returnObject } = runHook({ useCollectionState: collectionStateStub });
           let isChangeTriggered = false;
           watch(returnObject.currentSelection, () => {
             isChangeTriggered = true;
           });
           // act
-          userSelection.triggerSelectionChangedEvent(newSelectedScriptsArrayReference);
+          scriptSelectionStub.triggerSelectionChangedEvent(newSelectedScriptsArrayReference);
           await nextTick();
           // assert
           expect(isChangeTriggered).to.equal(true);
@@ -174,17 +192,19 @@ describe('useUserSelectionState', () => {
         it('with same selected scripts array reference', async () => {
           // arrange
           const sharedSelectedScriptsReference = [];
-          const userSelection = new UserSelectionStub([])
+          const scriptSelectionStub = new ScriptSelectionStub()
             .withSelectedScripts(sharedSelectedScriptsReference);
           const collectionStateStub = new UseCollectionStateStub()
-            .withState(new CategoryCollectionStateStub().withSelection(userSelection));
+            .withState(new CategoryCollectionStateStub().withSelection(
+              new UserSelectionStub().withScripts(scriptSelectionStub),
+            ));
           const { returnObject } = runHook({ useCollectionState: collectionStateStub });
           let isChangeTriggered = false;
           watch(returnObject.currentSelection, () => {
             isChangeTriggered = true;
           });
           // act
-          userSelection.triggerSelectionChangedEvent(sharedSelectedScriptsReference);
+          scriptSelectionStub.triggerSelectionChangedEvent(sharedSelectedScriptsReference);
           await nextTick();
           // assert
           expect(isChangeTriggered).to.equal(true);
@@ -197,7 +217,7 @@ describe('useUserSelectionState', () => {
       // arrange
       const { returnObject, collectionStateStub } = runHook();
       const expectedSelection = collectionStateStub.state.selection;
-      let mutatedSelection: IUserSelection | undefined;
+      let mutatedSelection: UserSelection | undefined;
       const mutator: SelectionModifier = (selection) => {
         mutatedSelection = selection;
       };
@@ -210,10 +230,10 @@ describe('useUserSelectionState', () => {
     it('new state is modified once collection state is changed', async () => {
       // arrange
       const { returnObject, collectionStateStub } = runHook();
-      const expectedSelection = new UserSelectionStub([]);
+      const expectedSelection = new UserSelectionStub();
       const newCollectionState = new CategoryCollectionStateStub()
         .withSelection(expectedSelection);
-      let mutatedSelection: IUserSelection | undefined;
+      let mutatedSelection: UserSelection | undefined;
       const mutator: SelectionModifier = (selection) => {
         mutatedSelection = selection;
       };
@@ -231,12 +251,12 @@ describe('useUserSelectionState', () => {
     it('old state is not modified once collection state is changed', async () => {
       // arrange
       const oldState = new CategoryCollectionStateStub().withSelectedScripts([
-        new SelectedScriptStub('scriptFromOldState'),
+        new SelectedScriptStub(new ScriptStub('scriptFromOldState')),
       ]);
       const collectionStateStub = new UseCollectionStateStub()
         .withState(oldState);
       const { returnObject } = runHook({ useCollectionState: collectionStateStub });
-      const expectedSelection = new UserSelectionStub([]);
+      const expectedSelection = new UserSelectionStub();
       const newCollectionState = new CategoryCollectionStateStub()
         .withSelection(expectedSelection);
       let totalMutations = 0;
diff --git a/tests/unit/shared/Stubs/BatchedDebounceStub.ts b/tests/unit/shared/Stubs/BatchedDebounceStub.ts
new file mode 100644
index 00000000..3a557f2d
--- /dev/null
+++ b/tests/unit/shared/Stubs/BatchedDebounceStub.ts
@@ -0,0 +1,33 @@
+import { batchedDebounce } from '@/application/Common/Timing/BatchedDebounce';
+
+export class BatchedDebounceStub<T> {
+  public readonly callHistory = new Array<Parameters<typeof batchedDebounce>>();
+
+  public readonly collectedArgs = new Array<T>();
+
+  private executeImmediately = false;
+
+  public func = (
+    callback: (batches: readonly T[]) => void,
+    waitInMs: number,
+  ): (arg: T) => void => {
+    this.callHistory.push([callback, waitInMs]);
+    return (arg: T) => {
+      this.collectedArgs.push(arg);
+      if (this.executeImmediately) {
+        callback([arg]);
+      }
+    };
+  };
+
+  public withImmediateDebouncing(executeImmediately: boolean): this {
+    this.executeImmediately = executeImmediately;
+    return this;
+  }
+
+  public execute() {
+    this.callHistory
+      .map((call) => call[0])
+      .forEach((callback) => callback(this.collectedArgs));
+  }
+}
diff --git a/tests/unit/shared/Stubs/CategoryCollectionStateStub.ts b/tests/unit/shared/Stubs/CategoryCollectionStateStub.ts
index dce3aff4..986c0e79 100644
--- a/tests/unit/shared/Stubs/CategoryCollectionStateStub.ts
+++ b/tests/unit/shared/Stubs/CategoryCollectionStateStub.ts
@@ -2,16 +2,17 @@ import { IApplicationCode } from '@/application/Context/State/Code/IApplicationC
 import { IUserFilter } from '@/application/Context/State/Filter/IUserFilter';
 import { ICategoryCollectionState } from '@/application/Context/State/ICategoryCollectionState';
 import { OperatingSystem } from '@/domain/OperatingSystem';
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
 import { IScript } from '@/domain/IScript';
 import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
 import { ICategoryCollection } from '@/domain/ICategoryCollection';
-import { IUserSelection } from '@/application/Context/State/Selection/IUserSelection';
+import { UserSelection } from '@/application/Context/State/Selection/UserSelection';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
 import { CategoryCollectionStub } from './CategoryCollectionStub';
 import { UserSelectionStub } from './UserSelectionStub';
 import { UserFilterStub } from './UserFilterStub';
 import { ApplicationCodeStub } from './ApplicationCodeStub';
 import { CategoryStub } from './CategoryStub';
+import { ScriptSelectionStub } from './ScriptSelectionStub';
 
 export class CategoryCollectionStateStub implements ICategoryCollectionState {
   public code: IApplicationCode = new ApplicationCodeStub();
@@ -24,10 +25,11 @@ export class CategoryCollectionStateStub implements ICategoryCollectionState {
 
   public collection: ICategoryCollection = new CategoryCollectionStub().withSomeActions();
 
-  public selection: IUserSelection = new UserSelectionStub([]);
+  public selection: UserSelection = new UserSelectionStub();
 
   constructor(readonly allScripts: IScript[] = [new ScriptStub('script-id')]) {
-    this.selection = new UserSelectionStub(allScripts);
+    this.selection = new UserSelectionStub()
+      .withScripts(new ScriptSelectionStub());
     this.collection = new CategoryCollectionStub()
       .withOs(this.os)
       .withTotalScripts(this.allScripts.length)
@@ -60,11 +62,14 @@ export class CategoryCollectionStateStub implements ICategoryCollectionState {
 
   public withSelectedScripts(initialScripts: readonly SelectedScript[]): this {
     return this.withSelection(
-      new UserSelectionStub([]).withSelectedScripts(initialScripts),
+      new UserSelectionStub().withScripts(
+        new ScriptSelectionStub()
+          .withSelectedScripts(initialScripts),
+      ),
     );
   }
 
-  public withSelection(selection: IUserSelection) {
+  public withSelection(selection: UserSelection) {
     this.selection = selection;
     return this;
   }
diff --git a/tests/unit/shared/Stubs/CategoryCollectionStub.ts b/tests/unit/shared/Stubs/CategoryCollectionStub.ts
index a14f11c1..aa5c7222 100644
--- a/tests/unit/shared/Stubs/CategoryCollectionStub.ts
+++ b/tests/unit/shared/Stubs/CategoryCollectionStub.ts
@@ -33,6 +33,13 @@ export class CategoryCollectionStub implements ICategoryCollection {
     return this;
   }
 
+  public withActions(...actions: readonly ICategory[]): this {
+    for (const action of actions) {
+      this.withAction(action);
+    }
+    return this;
+  }
+
   public withOs(os: OperatingSystem): this {
     this.os = os;
     return this;
diff --git a/tests/unit/shared/Stubs/CategorySelectionStub.ts b/tests/unit/shared/Stubs/CategorySelectionStub.ts
new file mode 100644
index 00000000..20af8f3b
--- /dev/null
+++ b/tests/unit/shared/Stubs/CategorySelectionStub.ts
@@ -0,0 +1,33 @@
+import { CategorySelection } from '@/application/Context/State/Selection/Category/CategorySelection';
+import { CategorySelectionChangeCommand } from '@/application/Context/State/Selection/Category/CategorySelectionChange';
+import { StubWithObservableMethodCalls } from './StubWithObservableMethodCalls';
+
+export class CategorySelectionStub
+  extends StubWithObservableMethodCalls<CategorySelection>
+  implements CategorySelection {
+  public isCategorySelected(categoryId: number, revert: boolean): boolean {
+    const call = this.callHistory.find(
+      (c) => c.methodName === 'processChanges'
+      && c.args[0].changes.some((change) => (
+        change.newStatus.isSelected === true
+        && change.newStatus.isReverted === revert
+        && change.categoryId === categoryId)),
+    );
+    return call !== undefined;
+  }
+
+  public areAllScriptsSelected(): boolean {
+    throw new Error('Method not implemented.');
+  }
+
+  public isAnyScriptSelected(): boolean {
+    throw new Error('Method not implemented.');
+  }
+
+  public processChanges(action: CategorySelectionChangeCommand): void {
+    this.registerMethodCall({
+      methodName: 'processChanges',
+      args: [action],
+    });
+  }
+}
diff --git a/tests/unit/shared/Stubs/CategoryStub.ts b/tests/unit/shared/Stubs/CategoryStub.ts
index 6ed4151f..95fe0af6 100644
--- a/tests/unit/shared/Stubs/CategoryStub.ts
+++ b/tests/unit/shared/Stubs/CategoryStub.ts
@@ -12,6 +12,8 @@ export class CategoryStub extends BaseEntity<number> implements ICategory {
 
   public readonly docs = new Array<string>();
 
+  private allScriptsRecursively: (readonly IScript[]) | undefined;
+
   public constructor(id: number) {
     super(id);
   }
@@ -21,13 +23,16 @@ export class CategoryStub extends BaseEntity<number> implements ICategory {
   }
 
   public getAllScriptsRecursively(): readonly IScript[] {
-    return [
-      ...this.scripts,
-      ...this.subCategories.flatMap((c) => c.getAllScriptsRecursively()),
-    ];
+    if (this.allScriptsRecursively === undefined) {
+      return [
+        ...this.scripts,
+        ...this.subCategories.flatMap((c) => c.getAllScriptsRecursively()),
+      ];
+    }
+    return this.allScriptsRecursively;
   }
 
-  public withScriptIds(...scriptIds: string[]): this {
+  public withScriptIds(...scriptIds: readonly string[]): this {
     return this.withScripts(
       ...scriptIds.map((id) => new ScriptStub(id)),
     );
@@ -40,6 +45,15 @@ export class CategoryStub extends BaseEntity<number> implements ICategory {
     return this;
   }
 
+  public withAllScriptIdsRecursively(...scriptIds: readonly string[]): this {
+    return this.withAllScriptsRecursively(...scriptIds.map((id) => new ScriptStub(id)));
+  }
+
+  public withAllScriptsRecursively(...scripts: IScript[]): this {
+    this.allScriptsRecursively = [...scripts];
+    return this;
+  }
+
   public withMandatoryScripts(): this {
     return this
       .withScript(new ScriptStub(`[${CategoryStub.name}] script-1`).withLevel(RecommendationLevel.Standard))
diff --git a/tests/unit/shared/Stubs/ScriptSelectionStub.ts b/tests/unit/shared/Stubs/ScriptSelectionStub.ts
new file mode 100644
index 00000000..20125413
--- /dev/null
+++ b/tests/unit/shared/Stubs/ScriptSelectionStub.ts
@@ -0,0 +1,89 @@
+import { ScriptSelection } from '@/application/Context/State/Selection/Script/ScriptSelection';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
+import { IScript } from '@/domain/IScript';
+import { ScriptSelectionChangeCommand } from '@/application/Context/State/Selection/Script/ScriptSelectionChange';
+import { StubWithObservableMethodCalls } from './StubWithObservableMethodCalls';
+import { EventSourceStub } from './EventSourceStub';
+import { SelectedScriptStub } from './SelectedScriptStub';
+
+export class ScriptSelectionStub
+  extends StubWithObservableMethodCalls<ScriptSelection>
+  implements ScriptSelection {
+  public readonly changed = new EventSourceStub<readonly SelectedScript[]>();
+
+  public selectedScripts: readonly SelectedScript[] = [];
+
+  public isSelectedResult: boolean | undefined;
+
+  public withSelectedScripts(selectedScripts: readonly SelectedScript[]): this {
+    this.selectedScripts = selectedScripts;
+    return this;
+  }
+
+  public triggerSelectionChangedEvent(scripts: readonly SelectedScript[]): this {
+    this.changed.notify(scripts);
+    return this;
+  }
+
+  public withIsSelectedResult(isSelected: boolean): this {
+    this.isSelectedResult = isSelected;
+    return this;
+  }
+
+  public isScriptSelected(scriptId: string, revert: boolean): boolean {
+    const call = this.callHistory.find(
+      (c) => c.methodName === 'processChanges'
+      && c.args[0].changes.some((change) => (
+        change.newStatus.isSelected === true
+        && change.newStatus.isReverted === revert
+        && change.scriptId === scriptId)),
+    );
+    return call !== undefined;
+  }
+
+  public isScriptDeselected(scriptId: string): boolean {
+    const call = this.callHistory.find(
+      (c) => c.methodName === 'processChanges'
+      && c.args[0].changes.some((change) => (
+        change.newStatus.isSelected === false
+        && change.scriptId === scriptId)),
+    );
+    return call !== undefined;
+  }
+
+  public processChanges(action: ScriptSelectionChangeCommand): void {
+    this.registerMethodCall({
+      methodName: 'processChanges',
+      args: [action],
+    });
+  }
+
+  public selectOnly(scripts: ReadonlyArray<IScript>): void {
+    this.registerMethodCall({
+      methodName: 'selectOnly',
+      args: [scripts],
+    });
+    this.selectedScripts = scripts.map((s) => new SelectedScriptStub(s));
+  }
+
+  public selectAll(): void {
+    this.registerMethodCall({
+      methodName: 'selectAll',
+      args: [],
+    });
+  }
+
+  public deselectAll(): void {
+    this.registerMethodCall({
+      methodName: 'deselectAll',
+      args: [],
+    });
+  }
+
+  public isSelected(): boolean {
+    if (this.isSelectedResult === undefined) {
+      throw new Error('Method not configured.');
+    }
+    return this.isSelectedResult;
+  }
+}
diff --git a/tests/unit/shared/Stubs/ScriptStub.ts b/tests/unit/shared/Stubs/ScriptStub.ts
index 80336cc0..fa6ba4aa 100644
--- a/tests/unit/shared/Stubs/ScriptStub.ts
+++ b/tests/unit/shared/Stubs/ScriptStub.ts
@@ -1,8 +1,8 @@
 import { BaseEntity } from '@/infrastructure/Entity/BaseEntity';
 import { IScript } from '@/domain/IScript';
 import { RecommendationLevel } from '@/domain/RecommendationLevel';
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
 import { IScriptCode } from '@/domain/IScriptCode';
+import { SelectedScriptStub } from './SelectedScriptStub';
 
 export class ScriptStub extends BaseEntity<string> implements IScript {
   public name = `name${this.id}`;
@@ -50,7 +50,7 @@ export class ScriptStub extends BaseEntity<string> implements IScript {
     return this;
   }
 
-  public toSelectedScript(isReverted = false): SelectedScript {
-    return new SelectedScript(this, isReverted);
+  public toSelectedScript(): SelectedScriptStub {
+    return new SelectedScriptStub(this);
   }
 }
diff --git a/tests/unit/shared/Stubs/SelectedScriptStub.ts b/tests/unit/shared/Stubs/SelectedScriptStub.ts
index 9a6153cd..aec73213 100644
--- a/tests/unit/shared/Stubs/SelectedScriptStub.ts
+++ b/tests/unit/shared/Stubs/SelectedScriptStub.ts
@@ -1,8 +1,26 @@
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
-import { ScriptStub } from './ScriptStub';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
+import { IScript } from '@/domain/IScript';
 
-export class SelectedScriptStub extends SelectedScript {
-  constructor(id: string, revert = false) {
-    super(new ScriptStub(id), revert);
+export class SelectedScriptStub implements SelectedScript {
+  public readonly script: IScript;
+
+  public readonly id: string;
+
+  public revert: boolean;
+
+  constructor(
+    script: IScript,
+  ) {
+    this.id = script.id;
+    this.script = script;
+  }
+
+  public withRevert(revert: boolean): this {
+    this.revert = revert;
+    return this;
+  }
+
+  public equals(): boolean {
+    throw new Error('Method not implemented.');
   }
 }
diff --git a/tests/unit/shared/Stubs/StubWithObservableMethodCalls.ts b/tests/unit/shared/Stubs/StubWithObservableMethodCalls.ts
index 37260f4d..270686e6 100644
--- a/tests/unit/shared/Stubs/StubWithObservableMethodCalls.ts
+++ b/tests/unit/shared/Stubs/StubWithObservableMethodCalls.ts
@@ -17,7 +17,7 @@ export abstract class StubWithObservableMethodCalls<T> {
   }
 }
 
-type MethodCall<T> = {
+export type MethodCall<T> = {
   [K in FunctionKeys<T>]: {
     readonly methodName: K;
     readonly args: T[K] extends (...args: infer A) => unknown ? A : never;
diff --git a/tests/unit/shared/Stubs/TimerStub.ts b/tests/unit/shared/Stubs/TimerStub.ts
new file mode 100644
index 00000000..606fd34d
--- /dev/null
+++ b/tests/unit/shared/Stubs/TimerStub.ts
@@ -0,0 +1,42 @@
+import { IEventSubscription } from '@/infrastructure/Events/IEventSource';
+import { EventSource } from '@/infrastructure/Events/EventSource';
+import { TimeoutType, Timer } from '@/application/Common/Timing/Timer';
+import { createMockTimeout } from './TimeoutStub';
+
+export class TimerStub implements Timer {
+  private timeChanged = new EventSource<number>();
+
+  private subscriptions = new Array<IEventSubscription>();
+
+  private currentTime = 0;
+
+  public setTimeout(callback: () => void, ms: number): TimeoutType {
+    const runTime = this.currentTime + ms;
+    const subscription = this.timeChanged.on((time) => {
+      if (time >= runTime) {
+        callback();
+        subscription.unsubscribe();
+      }
+    });
+    this.subscriptions.push(subscription);
+    const id = this.subscriptions.length - 1;
+    return createMockTimeout(id);
+  }
+
+  public clearTimeout(timeoutId: TimeoutType): void {
+    this.subscriptions[+timeoutId].unsubscribe();
+  }
+
+  public dateNow(): number {
+    return this.currentTime;
+  }
+
+  public tickNext(ms: number): void {
+    this.setCurrentTime(this.currentTime + ms);
+  }
+
+  public setCurrentTime(ms: number): void {
+    this.currentTime = ms;
+    this.timeChanged.notify(this.currentTime);
+  }
+}
diff --git a/tests/unit/shared/Stubs/UseUserSelectionStateStub.ts b/tests/unit/shared/Stubs/UseUserSelectionStateStub.ts
index a83faa4b..2ace7ba9 100644
--- a/tests/unit/shared/Stubs/UseUserSelectionStateStub.ts
+++ b/tests/unit/shared/Stubs/UseUserSelectionStateStub.ts
@@ -1,14 +1,15 @@
 import { shallowRef } from 'vue';
 import type { SelectionModifier, useUserSelectionState } from '@/presentation/components/Shared/Hooks/UseUserSelectionState';
-import { IUserSelection } from '@/application/Context/State/Selection/IUserSelection';
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
+import { UserSelection } from '@/application/Context/State/Selection/UserSelection';
+import { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
 import { StubWithObservableMethodCalls } from './StubWithObservableMethodCalls';
 import { UserSelectionStub } from './UserSelectionStub';
+import { ScriptSelectionStub } from './ScriptSelectionStub';
 
 export class UseUserSelectionStateStub
   extends StubWithObservableMethodCalls<ReturnType<typeof useUserSelectionState>> {
-  private readonly currentSelection = shallowRef<IUserSelection>(
-    new UserSelectionStub([]),
+  private readonly currentSelection = shallowRef<UserSelection>(
+    new UserSelectionStub(),
   );
 
   private modifyCurrentSelection(mutator: SelectionModifier) {
@@ -19,19 +20,21 @@ export class UseUserSelectionStateStub
     });
   }
 
-  public withUserSelection(userSelection: IUserSelection): this {
+  public withUserSelection(userSelection: UserSelection): this {
     this.currentSelection.value = userSelection;
     return this;
   }
 
   public withSelectedScripts(selectedScripts: readonly SelectedScript[]): this {
     return this.withUserSelection(
-      new UserSelectionStub(selectedScripts.map((s) => s.script))
-        .withSelectedScripts(selectedScripts),
+      new UserSelectionStub()
+        .withScripts(
+          new ScriptSelectionStub().withSelectedScripts(selectedScripts),
+        ),
     );
   }
 
-  public get selection(): IUserSelection {
+  public get selection(): UserSelection {
     return this.currentSelection.value;
   }
 
diff --git a/tests/unit/shared/Stubs/UserSelectionStub.ts b/tests/unit/shared/Stubs/UserSelectionStub.ts
index d21fcbc2..5ba8add6 100644
--- a/tests/unit/shared/Stubs/UserSelectionStub.ts
+++ b/tests/unit/shared/Stubs/UserSelectionStub.ts
@@ -1,91 +1,21 @@
-import { IUserSelection } from '@/application/Context/State/Selection/IUserSelection';
-import { SelectedScript } from '@/application/Context/State/Selection/SelectedScript';
-import { IScript } from '@/domain/IScript';
-import { StubWithObservableMethodCalls } from './StubWithObservableMethodCalls';
-import { EventSourceStub } from './EventSourceStub';
+import { CategorySelection } from '@/application/Context/State/Selection/Category/CategorySelection';
+import { ScriptSelection } from '@/application/Context/State/Selection/Script/ScriptSelection';
+import { UserSelection } from '@/application/Context/State/Selection/UserSelection';
+import { CategorySelectionStub } from './CategorySelectionStub';
+import { ScriptSelectionStub } from './ScriptSelectionStub';
 
-export class UserSelectionStub
-  extends StubWithObservableMethodCalls<IUserSelection>
-  implements IUserSelection {
-  public readonly changed = new EventSourceStub<readonly SelectedScript[]>();
+export class UserSelectionStub implements UserSelection {
+  public categories: CategorySelection = new CategorySelectionStub();
 
-  public selectedScripts: readonly SelectedScript[] = [];
+  public scripts: ScriptSelection = new ScriptSelectionStub();
 
-  constructor(private readonly allScripts: readonly IScript[]) {
-    super();
-  }
-
-  public withSelectedScripts(selectedScripts: readonly SelectedScript[]): this {
-    this.selectedScripts = selectedScripts;
+  public withCategories(categories: CategorySelection): this {
+    this.categories = categories;
     return this;
   }
 
-  public triggerSelectionChangedEvent(scripts: readonly SelectedScript[]): this {
-    this.changed.notify(scripts);
+  public withScripts(scripts: ScriptSelection): this {
+    this.scripts = scripts;
     return this;
   }
-
-  public isScriptAdded(scriptId: string): boolean {
-    const call = this.callHistory.find(
-      (c) => c.methodName === 'addSelectedScript' && c.args[0] === scriptId,
-    );
-    return call !== undefined;
-  }
-
-  public isScriptRemoved(scriptId: string): boolean {
-    const call = this.callHistory.find(
-      (c) => c.methodName === 'removeSelectedScript' && c.args[0] === scriptId,
-    );
-    return call !== undefined;
-  }
-
-  public areAllSelected(): boolean {
-    throw new Error('Method not implemented.');
-  }
-
-  public isAnySelected(): boolean {
-    throw new Error('Method not implemented.');
-  }
-
-  public removeAllInCategory(): void {
-    throw new Error('Method not implemented.');
-  }
-
-  public addOrUpdateAllInCategory(): void {
-    throw new Error('Method not implemented.');
-  }
-
-  public addSelectedScript(scriptId: string, revert: boolean): void {
-    this.registerMethodCall({
-      methodName: 'addSelectedScript',
-      args: [scriptId, revert],
-    });
-  }
-
-  public addOrUpdateSelectedScript(): void {
-    throw new Error('Method not implemented.');
-  }
-
-  public removeSelectedScript(scriptId: string): void {
-    this.registerMethodCall({
-      methodName: 'removeSelectedScript',
-      args: [scriptId],
-    });
-  }
-
-  public selectOnly(scripts: ReadonlyArray<IScript>): void {
-    this.selectedScripts = scripts.map((s) => new SelectedScript(s, false));
-  }
-
-  public isSelected(): boolean {
-    throw new Error('Method not implemented.');
-  }
-
-  public selectAll(): void {
-    this.selectOnly(this.allScripts);
-  }
-
-  public deselectAll(): void {
-    this.selectedScripts = [];
-  }
 }