Fix loss of tree node state when switching views

This commit fixes an issue where the check state of categories was lost
when toggling between card and tree views. This is solved by immediately
emitting node state changes for all nodes. This ensures consistent view
transitions without any loss of node state information.

Furthermore, this commit includes added unit tests for the modified code
sections.

tests/unit/presentation/components/Scripts/View/Tree/TreeView/Rendering/TimeoutDelayScheduler.spec.ts

@@ -0,0 +1,83 @@
+import { describe, it, expect } from 'vitest';
+import { TimeFunctions, TimeoutDelayScheduler } from '@/presentation/components/Scripts/View/Tree/TreeView/Rendering/TimeoutDelayScheduler';
+import { StubWithObservableMethodCalls } from '@tests/unit/shared/Stubs/StubWithObservableMethodCalls';
+
+describe('TimeoutDelayScheduler', () => {
+  describe('scheduleNext', () => {
+    describe('when setting a new timeout', () => {
+      it('sets callback correctly', () => {
+        // arrange
+        const timerStub = new TimeFunctionsStub();
+        const scheduler = new TimeoutDelayScheduler(timerStub);
+        const expectedCallback = () => { /* NO OP */ };
+        // act
+        scheduler.scheduleNext(expectedCallback, 3131);
+        // assert
+        const setTimeoutCalls = timerStub.callHistory.filter((c) => c.methodName === 'setTimeout');
+        expect(setTimeoutCalls).to.have.lengthOf(1);
+        const [actualCallback] = setTimeoutCalls[0].args;
+        expect(actualCallback).toBe(expectedCallback);
+      });
+      it('sets delay correctly', () => {
+        // arrange
+        const timerStub = new TimeFunctionsStub();
+        const scheduler = new TimeoutDelayScheduler(timerStub);
+        const expectedDelay = 100;
+        // act
+        scheduler.scheduleNext(() => {}, expectedDelay);
+        // assert
+        const setTimeoutCalls = timerStub.callHistory.filter((c) => c.methodName === 'setTimeout');
+        expect(setTimeoutCalls).to.have.lengthOf(1);
+        const [,actualDelay] = setTimeoutCalls[0].args;
+        expect(actualDelay).toBe(expectedDelay);
+      });
+      it('does not clear any timeout if none was previously set', () => {
+        // arrange
+        const timerStub = new TimeFunctionsStub();
+        const scheduler = new TimeoutDelayScheduler(timerStub);
+        // act
+        scheduler.scheduleNext(() => {}, 100);
+        // assert
+        const clearTimeoutCalls = timerStub.callHistory.filter((c) => c.methodName === 'clearTimeout');
+        expect(clearTimeoutCalls.length).toBe(0);
+      });
+    });
+    describe('when rescheduling a timeout', () => {
+      it('clears the previous timeout', () => {
+        // arrange
+        const timerStub = new TimeFunctionsStub();
+        const scheduler = new TimeoutDelayScheduler(timerStub);
+        const idOfFirstSetTimeoutCall = 1;
+        // act
+        scheduler.scheduleNext(() => {}, 100);
+        scheduler.scheduleNext(() => {}, 200);
+        // assert
+        const setTimeoutCalls = timerStub.callHistory.filter((c) => c.methodName === 'setTimeout');
+        expect(setTimeoutCalls.length).toBe(2);
+        const clearTimeoutCalls = timerStub.callHistory.filter((c) => c.methodName === 'clearTimeout');
+        expect(clearTimeoutCalls.length).toBe(1);
+        const [actualId] = clearTimeoutCalls[0].args;
+        expect(actualId).toBe(idOfFirstSetTimeoutCall);
+      });
+    });
+  });
+});
+
+class TimeFunctionsStub
+  extends StubWithObservableMethodCalls<TimeFunctions>
+  implements TimeFunctions {
+  public clearTimeout(id: ReturnType<typeof setTimeout>): void {
+    this.registerMethodCall({
+      methodName: 'clearTimeout',
+      args: [id],
+    });
+  }
+
+  public setTimeout(callback: () => void, delayInMs: number): ReturnType<typeof setTimeout> {
+    this.registerMethodCall({
+      methodName: 'setTimeout',
+      args: [callback, delayInMs],
+    });
+    return this.callHistory.filter((c) => c.methodName === 'setTimeout').length as unknown as ReturnType<typeof setTimeout>;
+  }
+}

tests/unit/presentation/components/Scripts/View/Tree/TreeView/Rendering/UseGradualNodeRendering.spec.ts

@@ -0,0 +1,284 @@
+import { describe, it, expect } from 'vitest';
+import { WatchSource } from 'vue';
+import { useGradualNodeRendering } from '@/presentation/components/Scripts/View/Tree/TreeView/Rendering/UseGradualNodeRendering';
+import { TreeRoot } from '@/presentation/components/Scripts/View/Tree/TreeView/TreeRoot/TreeRoot';
+import { TreeRootStub } from '@tests/unit/shared/Stubs/TreeRootStub';
+import { UseNodeStateChangeAggregatorStub } from '@tests/unit/shared/Stubs/UseNodeStateChangeAggregatorStub';
+import { UseCurrentTreeNodesStub } from '@tests/unit/shared/Stubs/UseCurrentTreeNodesStub';
+import { TreeNodeStub } from '@tests/unit/shared/Stubs/TreeNodeStub';
+import { TreeNodeStateAccessStub } from '@tests/unit/shared/Stubs/TreeNodeStateAccessStub';
+import { QueryableNodesStub } from '@tests/unit/shared/Stubs/QueryableNodesStub';
+import { NodeStateChangeEventArgsStub } from '@tests/unit/shared/Stubs/NodeStateChangeEventArgsStub';
+import { TreeNodeStateDescriptorStub } from '@tests/unit/shared/Stubs/TreeNodeStateDescriptorStub';
+import { DelaySchedulerStub } from '@tests/unit/shared/Stubs/DelaySchedulerStub';
+import { DelayScheduler } from '@/presentation/components/Scripts/View/Tree/TreeView/Rendering/DelayScheduler';
+import { TreeNode } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/TreeNode';
+
+describe('useGradualNodeRendering', () => {
+  it('watches nodes on specified tree', () => {
+    // arrange
+    const expectedWatcher = () => new TreeRootStub();
+    const currentTreeNodesStub = new UseCurrentTreeNodesStub();
+    const builder = new UseGradualNodeRenderingBuilder()
+      .withCurrentTreeNodes(currentTreeNodesStub)
+      .withTreeWatcher(expectedWatcher);
+    // act
+    builder.call();
+    // assert
+    const actualWatcher = currentTreeNodesStub.treeWatcher;
+    expect(actualWatcher).to.equal(expectedWatcher);
+  });
+  describe('shouldRender', () => {
+    describe('on visibility toggle', () => {
+      const scenarios: ReadonlyArray<{
+        readonly description: string;
+        readonly oldVisibilityState: boolean;
+        readonly newVisibilityState: boolean;
+        readonly expectedRenderStatus: boolean;
+      }> = [
+        {
+          description: 'renders node when made visible',
+          oldVisibilityState: false,
+          newVisibilityState: true,
+          expectedRenderStatus: true,
+        },
+        {
+          description: 'does not render node when hidden',
+          oldVisibilityState: true,
+          newVisibilityState: false,
+          expectedRenderStatus: false,
+        },
+      ];
+      scenarios.forEach(({
+        description, newVisibilityState, oldVisibilityState, expectedRenderStatus,
+      }) => {
+        it(description, () => {
+          // arrange
+          const node = createNodeWithVisibility(oldVisibilityState);
+          const nodesStub = new UseCurrentTreeNodesStub()
+            .withQueryableNodes(new QueryableNodesStub().withFlattenedNodes([node]));
+          const aggregatorStub = new UseNodeStateChangeAggregatorStub();
+          const delaySchedulerStub = new DelaySchedulerStub();
+          const builder = new UseGradualNodeRenderingBuilder()
+            .withCurrentTreeNodes(nodesStub)
+            .withChangeAggregator(aggregatorStub)
+            .withDelayScheduler(delaySchedulerStub);
+          const change = new NodeStateChangeEventArgsStub()
+            .withNode(node)
+            .withOldState(new TreeNodeStateDescriptorStub().withVisibility(oldVisibilityState))
+            .withNewState(new TreeNodeStateDescriptorStub().withVisibility(newVisibilityState));
+          // act
+          const strategy = builder.call();
+          aggregatorStub.notifyChange(change);
+          const actualRenderStatus = strategy.shouldRender(node);
+          // assert
+          expect(actualRenderStatus).to.equal(expectedRenderStatus);
+        });
+      });
+    });
+    describe('on initial nodes', () => {
+      const scenarios: ReadonlyArray<{
+        readonly description: string;
+        readonly schedulerTicks: number;
+        readonly initialBatchSize: number;
+        readonly subsequentBatchSize: number;
+        readonly nodes: readonly TreeNode[];
+        readonly expectedRenderStatuses: readonly number[],
+      }> = [
+        (() => {
+          const totalNodes = 10;
+          return {
+            description: 'does not render if all nodes are hidden',
+            schedulerTicks: 0,
+            initialBatchSize: 5,
+            subsequentBatchSize: 2,
+            nodes: createNodesWithVisibility(false, totalNodes),
+            expectedRenderStatuses: new Array(totalNodes).fill(false),
+          };
+        })(),
+        (() => {
+          const expectedRenderStatuses = [
+            false, false, true, true, false,
+          ];
+          const nodes = expectedRenderStatuses.map((status) => createNodeWithVisibility(status));
+          return {
+            description: 'renders only visible nodes',
+            schedulerTicks: 0,
+            initialBatchSize: nodes.length,
+            subsequentBatchSize: 2,
+            nodes,
+            expectedRenderStatuses,
+          };
+        })(),
+        (() => {
+          const initialBatchSize = 5;
+          return {
+            description: 'renders initial nodes immediately',
+            schedulerTicks: 0,
+            initialBatchSize,
+            subsequentBatchSize: 2,
+            nodes: createNodesWithVisibility(true, initialBatchSize),
+            expectedRenderStatuses: new Array(initialBatchSize).fill(true),
+          };
+        })(),
+        (() => {
+          const initialBatchSize = 5;
+          const subsequentBatchSize = 2;
+          const totalNodes = initialBatchSize + subsequentBatchSize * 2;
+          return {
+            description: 'does not render subsequent node batches immediately',
+            schedulerTicks: 0,
+            initialBatchSize,
+            subsequentBatchSize,
+            nodes: createNodesWithVisibility(true, totalNodes),
+            expectedRenderStatuses: [
+              ...new Array(initialBatchSize).fill(true),
+              ...new Array(totalNodes - initialBatchSize).fill(false),
+            ],
+          };
+        })(),
+        (() => {
+          const initialBatchSize = 5;
+          const subsequentBatchSize = 2;
+          const totalNodes = initialBatchSize + subsequentBatchSize * 2;
+          return {
+            description: 'eventually renders next subsequent node batch',
+            schedulerTicks: 1,
+            initialBatchSize,
+            subsequentBatchSize,
+            nodes: createNodesWithVisibility(true, totalNodes),
+            expectedRenderStatuses: [
+              ...new Array(initialBatchSize).fill(true),
+              ...new Array(subsequentBatchSize).fill(true), // first batch
+              ...new Array(subsequentBatchSize).fill(false), // second batch
+            ],
+          };
+        })(),
+        (() => {
+          const initialBatchSize = 5;
+          const totalSubsequentBatches = 2;
+          const subsequentBatchSize = 2;
+          const totalNodes = initialBatchSize + subsequentBatchSize * totalSubsequentBatches;
+          return {
+            description: 'eventually renders all subsequent node batches',
+            schedulerTicks: subsequentBatchSize,
+            initialBatchSize,
+            subsequentBatchSize,
+            nodes: createNodesWithVisibility(true, totalNodes),
+            expectedRenderStatuses: new Array(totalNodes).fill(true),
+          };
+        })(),
+      ];
+      scenarios.forEach(({
+        description, nodes, schedulerTicks, initialBatchSize,
+        subsequentBatchSize, expectedRenderStatuses,
+      }) => {
+        it(description, () => {
+          // arrange
+          const delaySchedulerStub = new DelaySchedulerStub();
+          const nodesStub = new UseCurrentTreeNodesStub()
+            .withQueryableNodes(new QueryableNodesStub().withFlattenedNodes(nodes));
+          const builder = new UseGradualNodeRenderingBuilder()
+            .withCurrentTreeNodes(nodesStub)
+            .withInitialBatchSize(initialBatchSize)
+            .withSubsequentBatchSize(subsequentBatchSize)
+            .withDelayScheduler(delaySchedulerStub);
+          // act
+          const strategy = builder.call();
+          Array.from({ length: schedulerTicks }).forEach(
+            () => delaySchedulerStub.runNextScheduled(),
+          );
+          const actualRenderStatuses = nodes.map((node) => strategy.shouldRender(node));
+          // expect
+          expect(actualRenderStatuses).to.deep.equal(expectedRenderStatuses);
+        });
+      });
+    });
+  });
+  it('skips scheduling when no nodes to render', () => {
+    // arrange
+    const nodes = [];
+    const nodesStub = new UseCurrentTreeNodesStub()
+      .withQueryableNodes(new QueryableNodesStub().withFlattenedNodes(nodes));
+    const delaySchedulerStub = new DelaySchedulerStub();
+    const builder = new UseGradualNodeRenderingBuilder()
+      .withCurrentTreeNodes(nodesStub)
+      .withDelayScheduler(delaySchedulerStub);
+    // act
+    builder.call();
+    // assert
+    expect(delaySchedulerStub.nextCallback).toBeUndefined();
+  });
+});
+
+function createNodesWithVisibility(
+  isVisible: boolean,
+  count: number,
+): readonly TreeNodeStub[] {
+  return Array.from({ length: count })
+    .map(() => createNodeWithVisibility(isVisible));
+}
+
+function createNodeWithVisibility(
+  isVisible: boolean,
+): TreeNodeStub {
+  return new TreeNodeStub()
+    .withState(
+      new TreeNodeStateAccessStub().withCurrentVisibility(isVisible),
+    );
+}
+
+class UseGradualNodeRenderingBuilder {
+  private changeAggregator = new UseNodeStateChangeAggregatorStub();
+
+  private treeWatcher: WatchSource<TreeRoot | undefined> = () => new TreeRootStub();
+
+  private currentTreeNodes = new UseCurrentTreeNodesStub();
+
+  private delayScheduler: DelayScheduler = new DelaySchedulerStub();
+
+  private initialBatchSize = 5;
+
+  private subsequentBatchSize = 3;
+
+  public withChangeAggregator(changeAggregator: UseNodeStateChangeAggregatorStub): this {
+    this.changeAggregator = changeAggregator;
+    return this;
+  }
+
+  public withCurrentTreeNodes(treeNodes: UseCurrentTreeNodesStub): this {
+    this.currentTreeNodes = treeNodes;
+    return this;
+  }
+
+  public withTreeWatcher(treeWatcher: WatchSource<TreeRoot | undefined>): this {
+    this.treeWatcher = treeWatcher;
+    return this;
+  }
+
+  public withDelayScheduler(delayScheduler: DelayScheduler): this {
+    this.delayScheduler = delayScheduler;
+    return this;
+  }
+
+  public withInitialBatchSize(initialBatchSize: number): this {
+    this.initialBatchSize = initialBatchSize;
+    return this;
+  }
+
+  public withSubsequentBatchSize(subsequentBatchSize: number): this {
+    this.subsequentBatchSize = subsequentBatchSize;
+    return this;
+  }
+
+  public call(): ReturnType<typeof useGradualNodeRendering> {
+    return useGradualNodeRendering(
+      this.treeWatcher,
+      this.changeAggregator.get(),
+      this.currentTreeNodes.get(),
+      this.delayScheduler,
+      this.initialBatchSize,
+      this.subsequentBatchSize,
+    );
+  }
+}

tests/unit/presentation/components/Scripts/View/Tree/TreeView/TreeRoot/Focus/SingleNodeCollectionFocusManager.spec.ts

@@ -87,6 +87,6 @@ describe('SingleNodeCollectionFocusManager', () => {
 function getNodeWithFocusState(isFocused: boolean): TreeNodeStub {
   return new TreeNodeStub()
     .withState(new TreeNodeStateAccessStub().withCurrent(
-      new TreeNodeStateDescriptorStub().withFocusState(isFocused),
+      new TreeNodeStateDescriptorStub().withFocus(isFocused),
     ));
 }

tests/unit/presentation/components/Scripts/View/Tree/TreeView/UseAutoUpdateChildrenCheckState.spec.ts

@@ -0,0 +1,218 @@
+import { describe, it, expect } from 'vitest';
+import { WatchSource } from 'vue';
+import { TreeRoot } from '@/presentation/components/Scripts/View/Tree/TreeView/TreeRoot/TreeRoot';
+import { useAutoUpdateChildrenCheckState } from '@/presentation/components/Scripts/View/Tree/TreeView/UseAutoUpdateChildrenCheckState';
+import { TreeNodeCheckState } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/State/CheckState';
+import { UseNodeStateChangeAggregatorStub } from '@tests/unit/shared/Stubs/UseNodeStateChangeAggregatorStub';
+import { getAbsentObjectTestCases } from '@tests/unit/shared/TestCases/AbsentTests';
+import { TreeRootStub } from '@tests/unit/shared/Stubs/TreeRootStub';
+import { TreeNodeStateDescriptorStub } from '@tests/unit/shared/Stubs/TreeNodeStateDescriptorStub';
+import { TreeNodeStateAccessStub, createAccessStubsFromCheckStates } from '@tests/unit/shared/Stubs/TreeNodeStateAccessStub';
+import { TreeNodeStateDescriptor } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/State/StateDescriptor';
+import { createChangeEvent } from '@tests/unit/shared/Stubs/NodeStateChangeEventArgsStub';
+import { TreeNodeStub } from '@tests/unit/shared/Stubs/TreeNodeStub';
+
+describe('useAutoUpdateChildrenCheckState', () => {
+  it('registers change handler', () => {
+    // arrange
+    const aggregatorStub = new UseNodeStateChangeAggregatorStub();
+    const builder = new UseAutoUpdateChildrenCheckStateBuilder()
+      .withChangeAggregator(aggregatorStub);
+    // act
+    builder.call();
+    // assert
+    expect(aggregatorStub.callback).toBeTruthy();
+  });
+  it('aggregate changes on specified tree', () => {
+    // arrange
+    const expectedWatcher = () => new TreeRootStub();
+    const aggregatorStub = new UseNodeStateChangeAggregatorStub();
+    const builder = new UseAutoUpdateChildrenCheckStateBuilder()
+      .withChangeAggregator(aggregatorStub)
+      .withTreeWatcher(expectedWatcher);
+    // act
+    builder.call();
+    // assert
+    const actualWatcher = aggregatorStub.treeWatcher;
+    expect(actualWatcher).to.equal(expectedWatcher);
+  });
+  describe('skips event handling', () => {
+    const scenarios: ReadonlyArray<{
+      readonly description: string,
+      readonly oldState: TreeNodeCheckState,
+      readonly newState: TreeNodeCheckState,
+      readonly childrenStates: readonly TreeNodeStateAccessStub[],
+      readonly isLeafNode: boolean,
+    }> = [
+      {
+        description: 'remains same: unchecked → unchecked',
+        oldState: TreeNodeCheckState.Unchecked,
+        newState: TreeNodeCheckState.Unchecked,
+        childrenStates: getAllPossibleCheckStates(),
+        isLeafNode: false,
+      },
+      {
+        description: 'remains same: checked → checked',
+        oldState: TreeNodeCheckState.Checked,
+        newState: TreeNodeCheckState.Checked,
+        childrenStates: getAllPossibleCheckStates(),
+        isLeafNode: false,
+      },
+      {
+        description: 'to indeterminate: checked → indeterminate',
+        oldState: TreeNodeCheckState.Checked,
+        newState: TreeNodeCheckState.Indeterminate,
+        childrenStates: getAllPossibleCheckStates(),
+        isLeafNode: false,
+      },
+      {
+        description: 'to indeterminate: unchecked → indeterminate',
+        oldState: TreeNodeCheckState.Unchecked,
+        newState: TreeNodeCheckState.Indeterminate,
+        childrenStates: getAllPossibleCheckStates(),
+        isLeafNode: false,
+      },
+      {
+        description: 'parent is leaf node: checked → unchecked',
+        oldState: TreeNodeCheckState.Checked,
+        newState: TreeNodeCheckState.Indeterminate,
+        childrenStates: getAllPossibleCheckStates(),
+        isLeafNode: true,
+      },
+      {
+        description: 'child node\'s state remains unchanged: unchecked → checked',
+        oldState: TreeNodeCheckState.Unchecked,
+        newState: TreeNodeCheckState.Checked,
+        childrenStates: createAccessStubsFromCheckStates([
+          TreeNodeCheckState.Checked,
+          TreeNodeCheckState.Checked,
+        ]),
+        isLeafNode: false,
+      },
+      {
+        description: 'child node\'s state remains unchanged: checked → unchecked',
+        oldState: TreeNodeCheckState.Checked,
+        newState: TreeNodeCheckState.Unchecked,
+        childrenStates: createAccessStubsFromCheckStates([
+          TreeNodeCheckState.Unchecked,
+          TreeNodeCheckState.Unchecked,
+        ]),
+        isLeafNode: false,
+      },
+    ];
+    scenarios.forEach(({
+      description, newState, oldState, childrenStates, isLeafNode,
+    }) => {
+      it(description, () => {
+        // arrange
+        const aggregatorStub = new UseNodeStateChangeAggregatorStub();
+        const builder = new UseAutoUpdateChildrenCheckStateBuilder()
+          .withChangeAggregator(aggregatorStub);
+        const changeEvent = createChangeEvent({
+          oldState: new TreeNodeStateDescriptorStub().withCheckState(oldState),
+          newState: new TreeNodeStateDescriptorStub().withCheckState(newState),
+          hierarchyBuilder: (hierarchy) => hierarchy
+            .withIsLeafNode(isLeafNode)
+            .withChildren(TreeNodeStub.fromStates(childrenStates)),
+        });
+        // act
+        builder.call();
+        aggregatorStub.notifyChange(changeEvent);
+        // assert
+        const changedStates = childrenStates
+          .filter((stub) => stub.isStateModificationRequested);
+        expect(changedStates).to.have.lengthOf(0);
+      });
+    });
+  });
+  describe('updates children as expected', () => {
+    const scenarios: ReadonlyArray<{
+      readonly description: string;
+      readonly oldState?: TreeNodeStateDescriptor;
+      readonly newState: TreeNodeStateDescriptor;
+    }> = [
+      {
+        description: 'unchecked → checked',
+        oldState: new TreeNodeStateDescriptorStub().withCheckState(TreeNodeCheckState.Unchecked),
+        newState: new TreeNodeStateDescriptorStub().withCheckState(TreeNodeCheckState.Checked),
+      },
+      {
+        description: 'checked → unchecked',
+        oldState: new TreeNodeStateDescriptorStub().withCheckState(TreeNodeCheckState.Checked),
+        newState: new TreeNodeStateDescriptorStub().withCheckState(TreeNodeCheckState.Unchecked),
+      },
+      {
+        description: 'indeterminate → unchecked',
+        oldState: new TreeNodeStateDescriptorStub()
+          .withCheckState(TreeNodeCheckState.Indeterminate),
+        newState: new TreeNodeStateDescriptorStub().withCheckState(TreeNodeCheckState.Unchecked),
+      },
+      {
+        description: 'indeterminate → checked',
+        oldState: new TreeNodeStateDescriptorStub()
+          .withCheckState(TreeNodeCheckState.Indeterminate),
+        newState: new TreeNodeStateDescriptorStub().withCheckState(TreeNodeCheckState.Checked),
+      },
+      ...getAbsentObjectTestCases().map((testCase) => ({
+        description: `absent old state: "${testCase.valueName}"`,
+        oldState: testCase.absentValue,
+        newState: new TreeNodeStateDescriptorStub().withCheckState(TreeNodeCheckState.Unchecked),
+      })),
+    ];
+    scenarios.forEach(({ description, newState, oldState }) => {
+      it(description, () => {
+        // arrange
+        const aggregatorStub = new UseNodeStateChangeAggregatorStub();
+        const childrenStates = getAllPossibleCheckStates();
+        const expectedChildrenStates = childrenStates.map(() => newState.checkState);
+        const builder = new UseAutoUpdateChildrenCheckStateBuilder()
+          .withChangeAggregator(aggregatorStub);
+        const changeEvent = createChangeEvent({
+          oldState,
+          newState,
+          hierarchyBuilder: (hierarchy) => hierarchy
+            .withIsLeafNode(false)
+            .withChildren(TreeNodeStub.fromStates(childrenStates)),
+        });
+        // act
+        builder.call();
+        aggregatorStub.notifyChange(changeEvent);
+        // assert
+        const actualStates = childrenStates.map((state) => state.current.checkState);
+        expect(actualStates).to.have.lengthOf(expectedChildrenStates.length);
+        expect(actualStates).to.have.members(expectedChildrenStates);
+      });
+    });
+  });
+});
+
+function getAllPossibleCheckStates() {
+  return createAccessStubsFromCheckStates([
+    TreeNodeCheckState.Checked,
+    TreeNodeCheckState.Unchecked,
+    TreeNodeCheckState.Indeterminate,
+  ]);
+}
+
+class UseAutoUpdateChildrenCheckStateBuilder {
+  private changeAggregator = new UseNodeStateChangeAggregatorStub();
+
+  private treeWatcher: WatchSource<TreeRoot | undefined> = () => new TreeRootStub();
+
+  public withChangeAggregator(changeAggregator: UseNodeStateChangeAggregatorStub): this {
+    this.changeAggregator = changeAggregator;
+    return this;
+  }
+
+  public withTreeWatcher(treeWatcher: WatchSource<TreeRoot | undefined>): this {
+    this.treeWatcher = treeWatcher;
+    return this;
+  }
+
+  public call(): ReturnType<typeof useAutoUpdateChildrenCheckState> {
+    return useAutoUpdateChildrenCheckState(
+      this.treeWatcher,
+      this.changeAggregator.get(),
+    );
+  }
+}

tests/unit/presentation/components/Scripts/View/Tree/TreeView/UseAutoUpdateParentCheckState.spec.ts

@@ -0,0 +1,206 @@
+import { describe, it, expect } from 'vitest';
+import { WatchSource } from 'vue';
+import { UseNodeStateChangeAggregatorStub } from '@tests/unit/shared/Stubs/UseNodeStateChangeAggregatorStub';
+import { TreeRootStub } from '@tests/unit/shared/Stubs/TreeRootStub';
+import { useAutoUpdateParentCheckState } from '@/presentation/components/Scripts/View/Tree/TreeView/UseAutoUpdateParentCheckState';
+import { TreeNodeStateDescriptorStub } from '@tests/unit/shared/Stubs/TreeNodeStateDescriptorStub';
+import { TreeNodeCheckState } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/State/CheckState';
+import { TreeNodeStub } from '@tests/unit/shared/Stubs/TreeNodeStub';
+import { HierarchyAccessStub } from '@tests/unit/shared/Stubs/HierarchyAccessStub';
+import { NodeStateChangeEventArgsStub, createChangeEvent } from '@tests/unit/shared/Stubs/NodeStateChangeEventArgsStub';
+import { TreeRoot } from '@/presentation/components/Scripts/View/Tree/TreeView/TreeRoot/TreeRoot';
+import { TreeNodeStateAccessStub, createAccessStubsFromCheckStates } from '@tests/unit/shared/Stubs/TreeNodeStateAccessStub';
+
+describe('useAutoUpdateParentCheckState', () => {
+  it('registers change handler', () => {
+    // arrange
+    const aggregatorStub = new UseNodeStateChangeAggregatorStub();
+    const builder = new UseAutoUpdateParentCheckStateBuilder()
+      .withChangeAggregator(aggregatorStub);
+    // act
+    builder.call();
+    // assert
+    expect(aggregatorStub.callback).toBeTruthy();
+  });
+  it('aggregate changes on specified tree', () => {
+    // arrange
+    const expectedWatcher = () => new TreeRootStub();
+    const aggregatorStub = new UseNodeStateChangeAggregatorStub();
+    const builder = new UseAutoUpdateParentCheckStateBuilder()
+      .withChangeAggregator(aggregatorStub)
+      .withTreeWatcher(expectedWatcher);
+    // act
+    builder.call();
+    // assert
+    const actualWatcher = aggregatorStub.treeWatcher;
+    expect(actualWatcher).to.equal(expectedWatcher);
+  });
+  it('does not throw if node has no parent', () => {
+    // arrange
+    const aggregatorStub = new UseNodeStateChangeAggregatorStub();
+    const changeEvent = new NodeStateChangeEventArgsStub()
+      .withNode(
+        new TreeNodeStub().withHierarchy(
+          new HierarchyAccessStub().withParent(undefined),
+        ),
+      );
+    const builder = new UseAutoUpdateParentCheckStateBuilder()
+      .withChangeAggregator(aggregatorStub);
+    // act
+    builder.call();
+    const act = () => aggregatorStub.notifyChange(changeEvent);
+    // assert
+    expect(act).to.not.throw();
+  });
+  describe('skips event handling', () => {
+    const scenarios: ReadonlyArray<{
+      readonly description: string,
+      readonly parentState: TreeNodeCheckState,
+      readonly newChildState: TreeNodeCheckState,
+      readonly oldChildState: TreeNodeCheckState,
+      readonly parentNodeChildrenStates: readonly TreeNodeCheckState[],
+    }> = [
+      {
+        description: 'check state remains the same',
+        parentState: TreeNodeCheckState.Checked,
+        newChildState: TreeNodeCheckState.Checked,
+        oldChildState: TreeNodeCheckState.Checked,
+        parentNodeChildrenStates: [TreeNodeCheckState.Checked], // these states do not matter
+      },
+      {
+        description: 'if parent node has same target state as children: Unchecked',
+        parentState: TreeNodeCheckState.Unchecked,
+        newChildState: TreeNodeCheckState.Unchecked,
+        oldChildState: TreeNodeCheckState.Checked,
+        parentNodeChildrenStates: [
+          TreeNodeCheckState.Unchecked,
+          TreeNodeCheckState.Unchecked,
+        ],
+      },
+      {
+        description: 'if parent node has same target state as children: Checked',
+        parentState: TreeNodeCheckState.Checked,
+        newChildState: TreeNodeCheckState.Checked,
+        oldChildState: TreeNodeCheckState.Unchecked,
+        parentNodeChildrenStates: [
+          TreeNodeCheckState.Checked,
+          TreeNodeCheckState.Checked,
+        ],
+      },
+      {
+        description: 'if parent node has same target state as children: Indeterminate',
+        parentState: TreeNodeCheckState.Indeterminate,
+        newChildState: TreeNodeCheckState.Indeterminate,
+        oldChildState: TreeNodeCheckState.Unchecked,
+        parentNodeChildrenStates: [
+          TreeNodeCheckState.Indeterminate,
+          TreeNodeCheckState.Indeterminate,
+        ],
+      },
+    ];
+    scenarios.forEach(({
+      description, newChildState, oldChildState, parentState, parentNodeChildrenStates,
+    }) => {
+      it(description, () => {
+        // arrange
+        const parentStateStub = new TreeNodeStateAccessStub()
+          .withCurrentCheckState(parentState);
+        const aggregatorStub = new UseNodeStateChangeAggregatorStub();
+        const builder = new UseAutoUpdateParentCheckStateBuilder()
+          .withChangeAggregator(aggregatorStub);
+        const changeEvent = createChangeEvent({
+          oldState: new TreeNodeStateDescriptorStub().withCheckState(oldChildState),
+          newState: new TreeNodeStateDescriptorStub().withCheckState(newChildState),
+          hierarchyBuilder: (hierarchy) => hierarchy.withParent(
+            new TreeNodeStub()
+              .withState(parentStateStub)
+              .withHierarchy(
+                new HierarchyAccessStub().withChildren(TreeNodeStub.fromStates(
+                  createAccessStubsFromCheckStates(parentNodeChildrenStates),
+                )),
+              ),
+          ),
+        });
+        // act
+        builder.call();
+        aggregatorStub.notifyChange(changeEvent);
+        // assert
+        expect(parentStateStub.isStateModificationRequested).to.equal(false);
+      });
+    });
+  });
+  describe('updates parent check state based on children', () => {
+    const scenarios: ReadonlyArray<{
+      readonly description: string;
+      readonly parentNodeChildrenStates: readonly TreeNodeCheckState[];
+      readonly expectedParentState: TreeNodeCheckState;
+    }> = [
+      {
+        description: 'all children checked → parent checked',
+        parentNodeChildrenStates: [TreeNodeCheckState.Checked, TreeNodeCheckState.Checked],
+        expectedParentState: TreeNodeCheckState.Checked,
+      },
+      {
+        description: 'all children unchecked → parent unchecked',
+        parentNodeChildrenStates: [TreeNodeCheckState.Unchecked, TreeNodeCheckState.Unchecked],
+        expectedParentState: TreeNodeCheckState.Unchecked,
+      },
+      {
+        description: 'mixed children states → parent indeterminate',
+        parentNodeChildrenStates: [TreeNodeCheckState.Checked, TreeNodeCheckState.Unchecked],
+        expectedParentState: TreeNodeCheckState.Indeterminate,
+      },
+    ];
+    scenarios.forEach(({ description, parentNodeChildrenStates, expectedParentState }) => {
+      it(description, () => {
+        // arrange
+        const aggregatorStub = new UseNodeStateChangeAggregatorStub();
+        const parentStateStub = new TreeNodeStateAccessStub()
+          .withCurrentCheckState(TreeNodeCheckState.Unchecked);
+        const changeEvent = createChangeEvent({
+          oldState: new TreeNodeStateDescriptorStub().withCheckState(TreeNodeCheckState.Unchecked),
+          newState: new TreeNodeStateDescriptorStub().withCheckState(TreeNodeCheckState.Checked),
+          hierarchyBuilder: (hierarchy) => hierarchy.withParent(
+            new TreeNodeStub()
+              .withState(parentStateStub)
+              .withHierarchy(
+                new HierarchyAccessStub().withChildren(TreeNodeStub.fromStates(
+                  createAccessStubsFromCheckStates(parentNodeChildrenStates),
+                )),
+              ),
+          ),
+        });
+        const builder = new UseAutoUpdateParentCheckStateBuilder()
+          .withChangeAggregator(aggregatorStub);
+        // act
+        builder.call();
+        aggregatorStub.notifyChange(changeEvent);
+        // assert
+        expect(parentStateStub.current.checkState).to.equal(expectedParentState);
+      });
+    });
+  });
+});
+
+class UseAutoUpdateParentCheckStateBuilder {
+  private changeAggregator = new UseNodeStateChangeAggregatorStub();
+
+  private treeWatcher: WatchSource<TreeRoot | undefined> = () => new TreeRootStub();
+
+  public withChangeAggregator(changeAggregator: UseNodeStateChangeAggregatorStub): this {
+    this.changeAggregator = changeAggregator;
+    return this;
+  }
+
+  public withTreeWatcher(treeWatcher: WatchSource<TreeRoot | undefined>): this {
+    this.treeWatcher = treeWatcher;
+    return this;
+  }
+
+  public call(): ReturnType<typeof useAutoUpdateParentCheckState> {
+    return useAutoUpdateParentCheckState(
+      this.treeWatcher,
+      this.changeAggregator.get(),
+    );
+  }
+}

tests/unit/presentation/components/Scripts/View/Tree/TreeView/UseNodeStateChangeAggregator.spec.ts

@@ -0,0 +1,348 @@
+import { describe, it, expect } from 'vitest';
+import { WatchSource, defineComponent, nextTick } from 'vue';
+import { shallowMount } from '@vue/test-utils';
+import { TreeRoot } from '@/presentation/components/Scripts/View/Tree/TreeView/TreeRoot/TreeRoot';
+import { useCurrentTreeNodes } from '@/presentation/components/Scripts/View/Tree/TreeView/UseCurrentTreeNodes';
+import { NodeStateChangeEventArgs, NodeStateChangeEventCallback, useNodeStateChangeAggregator } from '@/presentation/components/Scripts/View/Tree/TreeView/UseNodeStateChangeAggregator';
+import { TreeRootStub } from '@tests/unit/shared/Stubs/TreeRootStub';
+import { UseCurrentTreeNodesStub } from '@tests/unit/shared/Stubs/UseCurrentTreeNodesStub';
+import { itEachAbsentObjectValue } from '@tests/unit/shared/TestCases/AbsentTests';
+import { UseAutoUnsubscribedEventsStub } from '@tests/unit/shared/Stubs/UseAutoUnsubscribedEventsStub';
+import { InjectionKeys } from '@/presentation/injectionSymbols';
+import { TreeNodeStub } from '@tests/unit/shared/Stubs/TreeNodeStub';
+import { QueryableNodesStub } from '@tests/unit/shared/Stubs/QueryableNodesStub';
+import { TreeNode } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/TreeNode';
+import { TreeNodeStateDescriptor } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/State/StateDescriptor';
+import { TreeNodeStateDescriptorStub } from '@tests/unit/shared/Stubs/TreeNodeStateDescriptorStub';
+import { TreeNodeStateAccessStub } from '@tests/unit/shared/Stubs/TreeNodeStateAccessStub';
+import { IEventSubscriptionCollection } from '@/infrastructure/Events/IEventSubscriptionCollection';
+import { FunctionKeys } from '@/TypeHelpers';
+
+describe('useNodeStateChangeAggregator', () => {
+  it('watches nodes on specified tree', () => {
+    // arrange
+    const expectedWatcher = () => new TreeRootStub();
+    const currentTreeNodesStub = new UseCurrentTreeNodesStub();
+    const builder = new UseNodeStateChangeAggregatorBuilder()
+      .withCurrentTreeNodes(currentTreeNodesStub.get())
+      .withTreeWatcher(expectedWatcher);
+    // act
+    builder.mountWrapperComponent();
+    // assert
+    const actualWatcher = currentTreeNodesStub.treeWatcher;
+    expect(actualWatcher).to.equal(expectedWatcher);
+  });
+  describe('onNodeStateChange', () => {
+    describe('throws if callback is absent', () => {
+      itEachAbsentObjectValue((absentValue) => {
+        // arrange
+        const expectedError = 'missing callback';
+        const { returnObject } = new UseNodeStateChangeAggregatorBuilder()
+          .mountWrapperComponent();
+        // act
+        const act = () => returnObject.onNodeStateChange(absentValue);
+        // assert
+        expect(act).to.throw(expectedError);
+      });
+    });
+    describe('notifies current node states', () => {
+      const scenarios: ReadonlyArray<{
+        readonly description: string;
+        readonly expectedNodes: readonly TreeNode[];
+      }> = [
+        {
+          description: 'given single node',
+          expectedNodes: [
+            new TreeNodeStub().withId('expected-single-node'),
+          ],
+        },
+        {
+          description: 'given multiple nodes',
+          expectedNodes: [
+            new TreeNodeStub().withId('expected-first-node'),
+            new TreeNodeStub().withId('expected-second-node'),
+          ],
+        },
+      ];
+      scenarios.forEach(({
+        description, expectedNodes,
+      }) => {
+        describe('initially', () => {
+          it(description, async () => {
+            // arrange
+            const nodesStub = new UseCurrentTreeNodesStub()
+              .withQueryableNodes(createFlatCollection(expectedNodes));
+            const { returnObject } = new UseNodeStateChangeAggregatorBuilder()
+              .withCurrentTreeNodes(nodesStub.get())
+              .mountWrapperComponent();
+            const { callback, calledArgs } = createSpyingCallback();
+            // act
+            returnObject.onNodeStateChange(callback);
+            await nextTick();
+            // assert
+            assertCurrentNodeCalls({
+              actualArgs: calledArgs,
+              expectedNodes,
+              expectedNewStates: expectedNodes.map((n) => n.state.current),
+              expectedOldStates: new Array(expectedNodes.length).fill(undefined),
+            });
+          });
+        });
+        describe('when the tree changes', () => {
+          it(description, async () => {
+            // arrange
+            const nodesStub = new UseCurrentTreeNodesStub();
+            const { returnObject } = new UseNodeStateChangeAggregatorBuilder()
+              .withCurrentTreeNodes(nodesStub.get())
+              .mountWrapperComponent();
+            const { callback, calledArgs } = createSpyingCallback();
+            // act
+            returnObject.onNodeStateChange(callback);
+            calledArgs.length = 0;
+            nodesStub.triggerNewNodes(createFlatCollection(expectedNodes));
+            await nextTick();
+            // assert
+            assertCurrentNodeCalls({
+              actualArgs: calledArgs,
+              expectedNodes,
+              expectedNewStates: expectedNodes.map((n) => n.state.current),
+              expectedOldStates: new Array(expectedNodes.length).fill(undefined),
+            });
+          });
+        });
+        describe('when the callback changes', () => {
+          it(description, async () => {
+            // arrange
+            const nodesStub = new UseCurrentTreeNodesStub()
+              .withQueryableNodes(createFlatCollection(expectedNodes));
+            const { returnObject } = new UseNodeStateChangeAggregatorBuilder()
+              .withCurrentTreeNodes(nodesStub.get())
+              .mountWrapperComponent();
+            const { callback, calledArgs } = createSpyingCallback();
+            // act
+            returnObject.onNodeStateChange(() => { /* NOOP */ });
+            await nextTick();
+            returnObject.onNodeStateChange(callback);
+            await nextTick();
+            // assert
+            assertCurrentNodeCalls({
+              actualArgs: calledArgs,
+              expectedNodes,
+              expectedNewStates: expectedNodes.map((n) => n.state.current),
+              expectedOldStates: new Array(expectedNodes.length).fill(undefined),
+            });
+          });
+        });
+      });
+    });
+    describe('notifies future node states', () => {
+      const scenarios: ReadonlyArray<{
+        readonly description: string;
+        readonly initialNodes: readonly TreeNode[];
+        readonly changedNode: TreeNodeStub;
+        readonly expectedOldState: TreeNodeStateDescriptor;
+        readonly expectedNewState: TreeNodeStateDescriptor;
+      }> = [
+        (() => {
+          const changedNode = new TreeNodeStub().withId('expected-single-node');
+          return {
+            description: 'given single node state change',
+            initialNodes: [changedNode],
+            changedNode,
+            expectedOldState: new TreeNodeStateDescriptorStub().withFocus(false),
+            expectedNewState: new TreeNodeStateDescriptorStub().withFocus(true),
+          };
+        })(),
+        (() => {
+          const changedNode = new TreeNodeStub().withId('changed-second-node');
+          return {
+            description: 'given multiple nodes with a state change in one of them',
+            initialNodes: [
+              new TreeNodeStub().withId('unchanged-first-node'),
+              changedNode,
+            ],
+            changedNode,
+            expectedOldState: new TreeNodeStateDescriptorStub().withFocus(false),
+            expectedNewState: new TreeNodeStateDescriptorStub().withFocus(true),
+          };
+        })(),
+      ];
+
+      scenarios.forEach(({
+        description, initialNodes, changedNode, expectedOldState, expectedNewState,
+      }) => {
+        describe('when the state change event is triggered', () => {
+          it(description, async () => {
+            // arrange
+            const nodesStub = new UseCurrentTreeNodesStub()
+              .withQueryableNodes(createFlatCollection(initialNodes));
+            const nodeState = new TreeNodeStateAccessStub();
+            changedNode.withState(nodeState);
+            const { returnObject } = new UseNodeStateChangeAggregatorBuilder()
+              .withCurrentTreeNodes(nodesStub.get())
+              .mountWrapperComponent();
+            const { callback, calledArgs } = createSpyingCallback();
+            returnObject.onNodeStateChange(callback);
+            // act
+            await nextTick();
+            calledArgs.length = 0;
+            nodeState.triggerStateChangedEvent({
+              oldState: expectedOldState,
+              newState: expectedNewState,
+            });
+            await nextTick();
+            // assert
+            assertCurrentNodeCalls({
+              actualArgs: calledArgs,
+              expectedNodes: [changedNode],
+              expectedNewStates: [expectedNewState],
+              expectedOldStates: [expectedOldState],
+            });
+          });
+        });
+      });
+    });
+  });
+  describe('unsubscribes correctly', () => {
+    const scenarios: ReadonlyArray<{
+      readonly description: string;
+      readonly newNodes: readonly TreeNode[];
+      readonly expectedMethodName: FunctionKeys<IEventSubscriptionCollection>;
+    }> = [
+      {
+        description: 'unsubscribe and re-register events when nodes change',
+        newNodes: [new TreeNodeStub().withId('subsequent-node')],
+        expectedMethodName: 'unsubscribeAllAndRegister',
+      },
+      {
+        description: 'unsubscribes all when nodes change to empty',
+        newNodes: [],
+        expectedMethodName: 'unsubscribeAll',
+      },
+    ];
+    scenarios.forEach(({ description, expectedMethodName, newNodes }) => {
+      it(description, async () => {
+        // arrange
+        const initialNodes = [new TreeNodeStub().withId('initial-node')];
+        const nodesStub = new UseCurrentTreeNodesStub()
+          .withQueryableNodes(createFlatCollection(initialNodes));
+        const eventsStub = new UseAutoUnsubscribedEventsStub();
+        const { returnObject } = new UseNodeStateChangeAggregatorBuilder()
+          .withCurrentTreeNodes(nodesStub.get())
+          .withEventsStub(eventsStub)
+          .mountWrapperComponent();
+        // act
+        returnObject.onNodeStateChange(() => { /* NOOP */ });
+        await nextTick();
+        eventsStub.events.callHistory.length = 0;
+        nodesStub.triggerNewNodes(createFlatCollection(newNodes));
+        await nextTick();
+        // assert
+        const calls = eventsStub.events.callHistory;
+        expect(eventsStub.events.callHistory).has.lengthOf(1, calls.map((call) => call.methodName).join(', '));
+        const actualMethodName = calls[0].methodName;
+        expect(actualMethodName).to.equal(expectedMethodName);
+      });
+    });
+  });
+});
+
+function createSpyingCallback() {
+  const calledArgs = new Array<NodeStateChangeEventArgs>();
+  const callback: NodeStateChangeEventCallback = (args: NodeStateChangeEventArgs) => {
+    calledArgs.push(args);
+  };
+  return {
+    calledArgs,
+    callback,
+  };
+}
+
+function assertCurrentNodeCalls(context: {
+  readonly actualArgs: readonly NodeStateChangeEventArgs[];
+  readonly expectedNodes: readonly TreeNode[];
+  readonly expectedOldStates: readonly TreeNodeStateDescriptor[];
+  readonly expectedNewStates: readonly TreeNodeStateDescriptor[];
+}) {
+  const assertionMessage = buildAssertionMessage(
+    context.actualArgs,
+    context.expectedNodes,
+  );
+
+  expect(context.actualArgs).to.have.lengthOf(context.expectedNodes.length, assertionMessage);
+
+  const actualNodeIds = context.actualArgs.map((c) => c.node.id);
+  const expectedNodeIds = context.expectedNodes.map((node) => node.id);
+  expect(actualNodeIds).to.have.members(expectedNodeIds, assertionMessage);
+
+  const actualOldStates = context.actualArgs.map((c) => c.oldState);
+  expect(actualOldStates).to.have.deep.members(context.expectedOldStates, assertionMessage);
+
+  const actualNewStates = context.actualArgs.map((c) => c.newState);
+  expect(actualNewStates).to.have.deep.members(context.expectedNewStates, assertionMessage);
+}
+
+function buildAssertionMessage(
+  calledArgs: readonly NodeStateChangeEventArgs[],
+  nodes: readonly TreeNode[],
+): string {
+  return [
+    '\n',
+    `Expected nodes (${nodes.length}):`,
+    nodes.map((node) => `\tid: ${node.id}\n\tstate: ${JSON.stringify(node.state.current)}`).join('\n-\n'),
+    '\n',
+    `Actual called args (${calledArgs.length}):`,
+    calledArgs.map((args) => `\tid: ${args.node.id}\n\tnewState: ${JSON.stringify(args.newState)}`).join('\n-\n'),
+    '\n',
+  ].join('\n');
+}
+
+function createFlatCollection(nodes: readonly TreeNode[]): QueryableNodesStub {
+  return new QueryableNodesStub().withFlattenedNodes(nodes);
+}
+
+class UseNodeStateChangeAggregatorBuilder {
+  private treeWatcher: WatchSource<TreeRoot | undefined> = () => new TreeRootStub();
+
+  private currentTreeNodes: typeof useCurrentTreeNodes = new UseCurrentTreeNodesStub().get();
+
+  private events: UseAutoUnsubscribedEventsStub = new UseAutoUnsubscribedEventsStub();
+
+  public withTreeWatcher(treeWatcher: WatchSource<TreeRoot | undefined>): this {
+    this.treeWatcher = treeWatcher;
+    return this;
+  }
+
+  public withCurrentTreeNodes(treeNodes: typeof useCurrentTreeNodes): this {
+    this.currentTreeNodes = treeNodes;
+    return this;
+  }
+
+  public withEventsStub(events: UseAutoUnsubscribedEventsStub): this {
+    this.events = events;
+    return this;
+  }
+
+  public mountWrapperComponent() {
+    let returnObject: ReturnType<typeof useNodeStateChangeAggregator>;
+    const { treeWatcher, currentTreeNodes } = this;
+    const wrapper = shallowMount(
+      defineComponent({
+        setup() {
+          returnObject = useNodeStateChangeAggregator(treeWatcher, currentTreeNodes);
+        },
+        template: '<div></div>',
+      }),
+      {
+        provide: {
+          [InjectionKeys.useAutoUnsubscribedEvents as symbol]:
+            () => this.events.get(),
+        },
+      },
+    );
+    return {
+      wrapper,
+      returnObject,
+    };
+  }
+}

tests/unit/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseCollectionSelectionStateUpdater.spec.ts

@@ -1,17 +1,15 @@
-import { shallowMount } from '@vue/test-utils';
 import { describe, it, expect } from 'vitest';
-import { TreeNodeStateChangedEmittedEvent } from '@/presentation/components/Scripts/View/Tree/TreeView/Bindings/TreeNodeStateChangedEmittedEvent';
+import { shallowMount } from '@vue/test-utils';
 import { useCollectionSelectionStateUpdater } from '@/presentation/components/Scripts/View/Tree/TreeViewAdapter/UseCollectionSelectionStateUpdater';
 import { InjectionKeys } from '@/presentation/injectionSymbols';
 import { HierarchyAccessStub } from '@tests/unit/shared/Stubs/HierarchyAccessStub';
 import { TreeNodeStateAccessStub } from '@tests/unit/shared/Stubs/TreeNodeStateAccessStub';
 import { TreeNodeStub } from '@tests/unit/shared/Stubs/TreeNodeStub';
 import { UseCollectionStateStub } from '@tests/unit/shared/Stubs/UseCollectionStateStub';
-import { TreeNodeStateDescriptorStub } from '@tests/unit/shared/Stubs/TreeNodeStateDescriptorStub';
 import { TreeNodeCheckState } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/State/CheckState';
-import { NodeStateChangedEventStub } from '@tests/unit/shared/Stubs/NodeStateChangedEventStub';
 import { CategoryCollectionStateStub } from '@tests/unit/shared/Stubs/CategoryCollectionStateStub';
 import { UserSelectionStub } from '@tests/unit/shared/Stubs/UserSelectionStub';
+import { TreeNodeStateChangedEmittedEventStub } from '@tests/unit/shared/Stubs/TreeNodeStateChangedEmittedEventStub';
 
 describe('useCollectionSelectionStateUpdater', () => {
   describe('updateNodeSelection', () => {
@@ -19,16 +17,17 @@ describe('useCollectionSelectionStateUpdater', () => {
       it('does nothing', () => {
         // arrange
         const { returnObject, useStateStub } = mountWrapperComponent();
-        const mockEvent: TreeNodeStateChangedEmittedEvent = {
-          node: createTreeNodeStub({
-            isBranch: true,
-            currentState: TreeNodeCheckState.Checked,
-          }),
-          change: new NodeStateChangedEventStub().withCheckStateChange({
+        const mockEvent = new TreeNodeStateChangedEmittedEventStub()
+          .withNode(
+            createTreeNodeStub({
+              isBranch: true,
+              currentState: TreeNodeCheckState.Checked,
+            }),
+          )
+          .withCheckStateChange({
             oldState: TreeNodeCheckState.Checked,
             newState: TreeNodeCheckState.Unchecked,
-          }),
-        };
+          });
         // act
         returnObject.updateNodeSelection(mockEvent);
         // assert
@@ -40,16 +39,17 @@ describe('useCollectionSelectionStateUpdater', () => {
       it('does nothing', () => {
         // arrange
         const { returnObject, useStateStub } = mountWrapperComponent();
-        const mockEvent: TreeNodeStateChangedEmittedEvent = {
-          node: createTreeNodeStub({
-            isBranch: false,
-            currentState: TreeNodeCheckState.Checked,
-          }),
-          change: new NodeStateChangedEventStub().withCheckStateChange({
+        const mockEvent = new TreeNodeStateChangedEmittedEventStub()
+          .withNode(
+            createTreeNodeStub({
+              isBranch: false,
+              currentState: TreeNodeCheckState.Checked,
+            }),
+          )
+          .withCheckStateChange({
             oldState: TreeNodeCheckState.Checked,
             newState: TreeNodeCheckState.Checked,
-          }),
-        };
+          });
         // act
         returnObject.updateNodeSelection(mockEvent);
         // assert
@@ -64,19 +64,17 @@ describe('useCollectionSelectionStateUpdater', () => {
         const selectionStub = new UserSelectionStub([]);
         selectionStub.isSelected = () => false;
         useStateStub.withState(new CategoryCollectionStateStub().withSelection(selectionStub));
-        const mockEvent: TreeNodeStateChangedEmittedEvent = {
-          node: new TreeNodeStub()
-            .withHierarchy(new HierarchyAccessStub().withIsBranchNode(false))
-            .withState(new TreeNodeStateAccessStub().withCurrent(
-              new TreeNodeStateDescriptorStub().withCheckState(
-                TreeNodeCheckState.Checked,
-              ),
-            )),
-          change: new NodeStateChangedEventStub().withCheckStateChange({
+        const mockEvent = new TreeNodeStateChangedEmittedEventStub()
+          .withNode(
+            createTreeNodeStub({
+              isBranch: false,
+              currentState: TreeNodeCheckState.Checked,
+            }),
+          )
+          .withCheckStateChange({
             oldState: TreeNodeCheckState.Unchecked,
             newState: TreeNodeCheckState.Checked,
-          }),
-        };
+          });
         // act
         returnObject.updateNodeSelection(mockEvent);
         // assert
@@ -91,16 +89,17 @@ describe('useCollectionSelectionStateUpdater', () => {
         const selectionStub = new UserSelectionStub([]);
         selectionStub.isSelected = () => true;
         useStateStub.withState(new CategoryCollectionStateStub().withSelection(selectionStub));
-        const mockEvent: TreeNodeStateChangedEmittedEvent = {
-          node: createTreeNodeStub({
-            isBranch: false,
-            currentState: TreeNodeCheckState.Checked,
-          }),
-          change: new NodeStateChangedEventStub().withCheckStateChange({
+        const mockEvent = new TreeNodeStateChangedEmittedEventStub()
+          .withNode(
+            createTreeNodeStub({
+              isBranch: false,
+              currentState: TreeNodeCheckState.Checked,
+            }),
+          )
+          .withCheckStateChange({
             oldState: TreeNodeCheckState.Unchecked,
             newState: TreeNodeCheckState.Checked,
-          }),
-        };
+          });
         // act
         returnObject.updateNodeSelection(mockEvent);
         // assert
@@ -115,16 +114,17 @@ describe('useCollectionSelectionStateUpdater', () => {
         const selectionStub = new UserSelectionStub([]);
         selectionStub.isSelected = () => true;
         useStateStub.withState(new CategoryCollectionStateStub().withSelection(selectionStub));
-        const mockEvent: TreeNodeStateChangedEmittedEvent = {
-          node: createTreeNodeStub({
-            isBranch: false,
-            currentState: TreeNodeCheckState.Unchecked,
-          }),
-          change: new NodeStateChangedEventStub().withCheckStateChange({
+        const mockEvent = new TreeNodeStateChangedEmittedEventStub()
+          .withNode(
+            createTreeNodeStub({
+              isBranch: false,
+              currentState: TreeNodeCheckState.Unchecked,
+            }),
+          )
+          .withCheckStateChange({
             oldState: TreeNodeCheckState.Checked,
             newState: TreeNodeCheckState.Unchecked,
-          }),
-        };
+          });
         // act
         returnObject.updateNodeSelection(mockEvent);
         // assert
@@ -139,16 +139,17 @@ describe('useCollectionSelectionStateUpdater', () => {
         const selectionStub = new UserSelectionStub([]);
         selectionStub.isSelected = () => false;
         useStateStub.withState(new CategoryCollectionStateStub().withSelection(selectionStub));
-        const mockEvent: TreeNodeStateChangedEmittedEvent = {
-          node: createTreeNodeStub({
-            isBranch: false,
-            currentState: TreeNodeCheckState.Unchecked,
-          }),
-          change: new NodeStateChangedEventStub().withCheckStateChange({
+        const mockEvent = new TreeNodeStateChangedEmittedEventStub()
+          .withNode(
+            createTreeNodeStub({
+              isBranch: false,
+              currentState: TreeNodeCheckState.Unchecked,
+            }),
+          )
+          .withCheckStateChange({
             oldState: TreeNodeCheckState.Checked,
             newState: TreeNodeCheckState.Unchecked,
-          }),
-        };
+          });
         // act
         returnObject.updateNodeSelection(mockEvent);
         // assert
@@ -186,9 +187,5 @@ function createTreeNodeStub(scenario: {
 }) {
   return new TreeNodeStub()
     .withHierarchy(new HierarchyAccessStub().withIsBranchNode(scenario.isBranch))
-    .withState(new TreeNodeStateAccessStub().withCurrent(
-      new TreeNodeStateDescriptorStub().withCheckState(
-        scenario.currentState,
-      ),
-    ));
+    .withState(new TreeNodeStateAccessStub().withCurrentCheckState(scenario.currentState));
 }

tests/unit/shared/Stubs/DelaySchedulerStub.ts

@@ -0,0 +1,19 @@
+import { DelayScheduler } from '@/presentation/components/Scripts/View/Tree/TreeView/Rendering/DelayScheduler';
+
+export class DelaySchedulerStub implements DelayScheduler {
+  public nextCallback: () => void | undefined = undefined;
+
+  public scheduleNext(callback: () => void): void {
+    this.nextCallback = callback;
+  }
+
+  public runNextScheduled(): void {
+    if (!this.nextCallback) {
+      throw new Error('no callback is scheduled');
+    }
+    // Store the callback to prevent changes to this.nextCallback during execution
+    const callback = this.nextCallback;
+    this.nextCallback = undefined;
+    callback();
+  }
+}

tests/unit/shared/Stubs/EventSubscriptionCollectionStub.ts

@@ -44,7 +44,7 @@ export class EventSubscriptionCollectionStub
       methodName: 'unsubscribeAllAndRegister',
       args: [subscriptions],
     });
-    this.unsubscribeAll();
-    this.register(subscriptions);
+    // Not calling other methods to avoid registering method calls.
+    this.subscriptions.splice(0, this.subscriptions.length, ...subscriptions);
   }
 }

tests/unit/shared/Stubs/HierarchyAccessStub.ts

@@ -39,4 +39,9 @@ export class HierarchyAccessStub implements HierarchyAccess {
     this.isBranchNode = value;
     return this;
   }
+
+  public withIsLeafNode(value: boolean): this {
+    this.isLeafNode = value;
+    return this;
+  }
 }

tests/unit/shared/Stubs/NodeStateChangeEventArgsStub.ts

@@ -0,0 +1,48 @@
+import { NodeStateChangeEventArgs } from '@/presentation/components/Scripts/View/Tree/TreeView/UseNodeStateChangeAggregator';
+import { TreeNode } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/TreeNode';
+import { TreeNodeStateDescriptor } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/State/StateDescriptor';
+import { TreeNodeStub } from './TreeNodeStub';
+import { TreeNodeStateDescriptorStub } from './TreeNodeStateDescriptorStub';
+import { HierarchyAccessStub } from './HierarchyAccessStub';
+
+export class NodeStateChangeEventArgsStub implements NodeStateChangeEventArgs {
+  public node: TreeNode = new TreeNodeStub()
+    .withId(`[${NodeStateChangeEventArgsStub.name}] node-stub`);
+
+  public newState: TreeNodeStateDescriptor = new TreeNodeStateDescriptorStub();
+
+  public oldState?: TreeNodeStateDescriptor = new TreeNodeStateDescriptorStub();
+
+  public withNode(node: TreeNode): this {
+    this.node = node;
+    return this;
+  }
+
+  public withNewState(newState: TreeNodeStateDescriptor): this {
+    this.newState = newState;
+    return this;
+  }
+
+  public withOldState(oldState: TreeNodeStateDescriptor): this {
+    this.oldState = oldState;
+    return this;
+  }
+}
+
+export function createChangeEvent(scenario: {
+  readonly oldState?: TreeNodeStateDescriptor;
+  readonly newState: TreeNodeStateDescriptor;
+  readonly hierarchyBuilder?: (hierarchy: HierarchyAccessStub) => HierarchyAccessStub;
+}) {
+  let nodeHierarchy = new HierarchyAccessStub();
+  if (scenario.hierarchyBuilder) {
+    nodeHierarchy = scenario.hierarchyBuilder(nodeHierarchy);
+  }
+  const changeEvent = new NodeStateChangeEventArgsStub()
+    .withOldState(scenario.oldState)
+    .withNewState(scenario.newState)
+    .withNode(new TreeNodeStub()
+      .withId(`[${createChangeEvent.name}] node-stub`)
+      .withHierarchy(nodeHierarchy));
+  return changeEvent;
+}

tests/unit/shared/Stubs/NodeStateChangedEventStub.ts

@@ -1,4 +1,3 @@
-import { TreeNodeCheckState } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/State/CheckState';
 import { NodeStateChangedEvent } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/State/StateAccess';
 import { TreeNodeStateDescriptor } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/State/StateDescriptor';
 import { TreeNodeStateDescriptorStub } from '@tests/unit/shared/Stubs/TreeNodeStateDescriptorStub';
@@ -17,17 +16,4 @@ export class NodeStateChangedEventStub implements NodeStateChangedEvent {
     this.oldState = oldState;
     return this;
   }
-
-  public withCheckStateChange(change: {
-    readonly oldState: TreeNodeCheckState,
-    readonly newState: TreeNodeCheckState,
-  }) {
-    return this
-      .withOldState(
-        new TreeNodeStateDescriptorStub().withCheckState(change.oldState),
-      )
-      .withNewState(
-        new TreeNodeStateDescriptorStub().withCheckState(change.newState),
-      );
-  }
 }

tests/unit/shared/Stubs/QueryableNodesStub.ts

@@ -1,10 +1,16 @@
 import { TreeNode } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/TreeNode';
 import { QueryableNodes } from '@/presentation/components/Scripts/View/Tree/TreeView/TreeRoot/NodeCollection/Query/QueryableNodes';
+import { TreeNodeStub } from './TreeNodeStub';
 
 export class QueryableNodesStub implements QueryableNodes {
-  public rootNodes: readonly TreeNode[];
+  public rootNodes: readonly TreeNode[] = [
+    new TreeNodeStub().withId(`[${QueryableNodesStub.name}] root-node-stub`),
+  ];
 
-  public flattenedNodes: readonly TreeNode[];
+  public flattenedNodes: readonly TreeNode[] = [
+    new TreeNodeStub().withId(`[${QueryableNodesStub.name}] flattened-node-stub-1`),
+    new TreeNodeStub().withId(`[${QueryableNodesStub.name}] flattened-node-stub-2`),
+  ];
 
   public getNodeById(): TreeNode {
     throw new Error('Method not implemented.');

tests/unit/shared/Stubs/SingleNodeFocusManagerStub.ts

@@ -3,7 +3,8 @@ import { SingleNodeFocusManager } from '@/presentation/components/Scripts/View/T
 import { TreeNodeStub } from './TreeNodeStub';
 
 export class SingleNodeFocusManagerStub implements SingleNodeFocusManager {
-  public currentSingleFocusedNode: TreeNode = new TreeNodeStub();
+  public currentSingleFocusedNode: TreeNode = new TreeNodeStub()
+    .withId(`[${SingleNodeFocusManagerStub.name}] focused-node-stub`);
 
   setSingleFocus(): void { /* NOOP */ }
 }

tests/unit/shared/Stubs/TreeNodeCollectionStub.ts

@@ -1,9 +1,10 @@
 import { QueryableNodes } from '@/presentation/components/Scripts/View/Tree/TreeView/TreeRoot/NodeCollection/Query/QueryableNodes';
 import { TreeNodeCollection } from '@/presentation/components/Scripts/View/Tree/TreeView/TreeRoot/NodeCollection/TreeNodeCollection';
 import { EventSourceStub } from './EventSourceStub';
+import { QueryableNodesStub } from './QueryableNodesStub';
 
 export class TreeNodeCollectionStub implements TreeNodeCollection {
-  public nodes: QueryableNodes;
+  public nodes: QueryableNodes = new QueryableNodesStub();
 
   public nodesUpdated = new EventSourceStub<QueryableNodes>();
 

tests/unit/shared/Stubs/TreeNodeParserStub.ts

@@ -20,7 +20,8 @@ export function createTreeNodeParserStub() {
     if (result !== undefined) {
       return result.result;
     }
-    return data.map(() => new TreeNodeStub());
+    return data.map(() => new TreeNodeStub()
+      .withId(`[${createTreeNodeParserStub.name}] parsed-node-stub`));
   };
   return {
     registerScenario,

tests/unit/shared/Stubs/TreeNodeStateAccessStub.ts

@@ -1,10 +1,13 @@
 import { NodeStateChangedEvent, TreeNodeStateAccess, TreeNodeStateTransaction } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/State/StateAccess';
 import { TreeNodeStateDescriptor } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/State/StateDescriptor';
+import { TreeNodeCheckState } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/State/CheckState';
 import { TreeNodeStateDescriptorStub } from './TreeNodeStateDescriptorStub';
 import { EventSourceStub } from './EventSourceStub';
 import { TreeNodeStateTransactionStub } from './TreeNodeStateTransactionStub';
 
 export class TreeNodeStateAccessStub implements TreeNodeStateAccess {
+  public isStateModificationRequested = false;
+
   public current: TreeNodeStateDescriptor = new TreeNodeStateDescriptorStub();
 
   public changed: EventSourceStub<NodeStateChangedEvent> = new EventSourceStub();
@@ -32,6 +35,7 @@ export class TreeNodeStateAccessStub implements TreeNodeStateAccess {
       oldState,
       newState,
     });
+    this.isStateModificationRequested = true;
   }
 
   public triggerStateChangedEvent(event: NodeStateChangedEvent) {
@@ -42,4 +46,26 @@ export class TreeNodeStateAccessStub implements TreeNodeStateAccess {
     this.current = state;
     return this;
   }
+
+  public withCurrentCheckState(checkState: TreeNodeCheckState): this {
+    return this.withCurrent(
+      new TreeNodeStateDescriptorStub()
+        .withCheckState(checkState),
+    );
+  }
+
+  public withCurrentVisibility(isVisible: boolean): this {
+    return this.withCurrent(
+      new TreeNodeStateDescriptorStub()
+        .withVisibility(isVisible),
+    );
+  }
+}
+
+export function createAccessStubsFromCheckStates(
+  states: readonly TreeNodeCheckState[],
+): TreeNodeStateAccessStub[] {
+  return states.map(
+    (checkState) => new TreeNodeStateAccessStub().withCurrentCheckState(checkState),
+  );
 }

tests/unit/shared/Stubs/TreeNodeStateChangedEmittedEventStub.ts

@@ -0,0 +1,41 @@
+import { TreeNodeStateChangedEmittedEvent } from '@/presentation/components/Scripts/View/Tree/TreeView/Bindings/TreeNodeStateChangedEmittedEvent';
+import { TreeNodeCheckState } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/State/CheckState';
+import { TreeNodeStateDescriptor } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/State/StateDescriptor';
+import { ReadOnlyTreeNode } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/TreeNode';
+import { TreeNodeStateDescriptorStub } from './TreeNodeStateDescriptorStub';
+
+export class TreeNodeStateChangedEmittedEventStub implements TreeNodeStateChangedEmittedEvent {
+  public node: ReadOnlyTreeNode;
+
+  public oldState?: TreeNodeStateDescriptor;
+
+  public newState: TreeNodeStateDescriptor;
+
+  public withNode(node: ReadOnlyTreeNode): this {
+    this.node = node;
+    return this;
+  }
+
+  public withNewState(newState: TreeNodeStateDescriptor): this {
+    this.newState = newState;
+    return this;
+  }
+
+  public withOldState(oldState: TreeNodeStateDescriptor): this {
+    this.oldState = oldState;
+    return this;
+  }
+
+  public withCheckStateChange(change: {
+    readonly oldState: TreeNodeCheckState,
+    readonly newState: TreeNodeCheckState,
+  }) {
+    return this
+      .withOldState(
+        new TreeNodeStateDescriptorStub().withCheckState(change.oldState),
+      )
+      .withNewState(
+        new TreeNodeStateDescriptorStub().withCheckState(change.newState),
+      );
+  }
+}

tests/unit/shared/Stubs/TreeNodeStateDescriptorStub.ts

@@ -12,7 +12,7 @@ export class TreeNodeStateDescriptorStub implements TreeNodeStateDescriptor {
 
   public isFocused = false;
 
-  public withFocusState(isFocused: boolean): this {
+  public withFocus(isFocused: boolean): this {
     this.isFocused = isFocused;
     return this;
   }
@@ -21,4 +21,9 @@ export class TreeNodeStateDescriptorStub implements TreeNodeStateDescriptor {
     this.checkState = checkState;
     return this;
   }
+
+  public withVisibility(isVisible: boolean): this {
+    this.isVisible = isVisible;
+    return this;
+  }
 }

tests/unit/shared/Stubs/TreeNodeStub.ts

@@ -3,13 +3,24 @@ import { TreeNodeStateAccess } from '@/presentation/components/Scripts/View/Tree
 import { TreeNode } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/TreeNode';
 import { NodeMetadataStub } from './NodeMetadataStub';
 import { HierarchyAccessStub } from './HierarchyAccessStub';
+import { TreeNodeStateAccessStub } from './TreeNodeStateAccessStub';
 
 export class TreeNodeStub implements TreeNode {
-  public state: TreeNodeStateAccess;
+  public static fromStates(
+    states: readonly TreeNodeStateAccess[],
+  ): TreeNodeStub[] {
+    return states.map(
+      (state) => new TreeNodeStub()
+        .withId(`[${TreeNodeStub.fromStates.name}] node-stub`)
+        .withState(state),
+    );
+  }
+
+  public state: TreeNodeStateAccess = new TreeNodeStateAccessStub();
 
   public hierarchy: HierarchyAccess = new HierarchyAccessStub();
 
-  public id: string;
+  public id = 'tree-node-stub-id';
 
   public metadata?: object = new NodeMetadataStub();
 

tests/unit/shared/Stubs/UseAutoUnsubscribedEventsStub.ts

@@ -2,9 +2,11 @@ import { useAutoUnsubscribedEvents } from '@/presentation/components/Shared/Hook
 import { EventSubscriptionCollectionStub } from './EventSubscriptionCollectionStub';
 
 export class UseAutoUnsubscribedEventsStub {
+  public readonly events = new EventSubscriptionCollectionStub();
+
   public get(): ReturnType<typeof useAutoUnsubscribedEvents> {
     return {
-      events: new EventSubscriptionCollectionStub(),
+      events: this.events,
     };
   }
 }

tests/unit/shared/Stubs/UseCurrentTreeNodesStub.ts

@@ -0,0 +1,32 @@
+import {
+  WatchSource, readonly, shallowRef, triggerRef,
+} from 'vue';
+import { TreeRoot } from '@/presentation/components/Scripts/View/Tree/TreeView/TreeRoot/TreeRoot';
+import { useCurrentTreeNodes } from '@/presentation/components/Scripts/View/Tree/TreeView/UseCurrentTreeNodes';
+import { QueryableNodes } from '@/presentation/components/Scripts/View/Tree/TreeView/TreeRoot/NodeCollection/Query/QueryableNodes';
+import { QueryableNodesStub } from './QueryableNodesStub';
+
+export class UseCurrentTreeNodesStub {
+  public treeWatcher: WatchSource<TreeRoot> | undefined;
+
+  private nodes = shallowRef<QueryableNodes>(new QueryableNodesStub());
+
+  public withQueryableNodes(nodes: QueryableNodes): this {
+    this.nodes.value = nodes;
+    return this;
+  }
+
+  public triggerNewNodes(nodes: QueryableNodes) {
+    this.nodes.value = nodes;
+    triggerRef(this.nodes);
+  }
+
+  public get(): typeof useCurrentTreeNodes {
+    return (treeWatcher: WatchSource<TreeRoot>) => {
+      this.treeWatcher = treeWatcher;
+      return {
+        nodes: readonly(this.nodes),
+      };
+    };
+  }
+}

tests/unit/shared/Stubs/UseNodeStateChangeAggregatorStub.ts

@@ -0,0 +1,33 @@
+import { WatchSource } from 'vue';
+import { TreeRoot } from '@/presentation/components/Scripts/View/Tree/TreeView/TreeRoot/TreeRoot';
+import {
+  NodeStateChangeEventArgs,
+  NodeStateChangeEventCallback,
+  useNodeStateChangeAggregator,
+} from '@/presentation/components/Scripts/View/Tree/TreeView/UseNodeStateChangeAggregator';
+
+export class UseNodeStateChangeAggregatorStub {
+  public callback: NodeStateChangeEventCallback | undefined;
+
+  public treeWatcher: WatchSource<TreeRoot> | undefined;
+
+  public onNodeStateChange(callback: NodeStateChangeEventCallback) {
+    this.callback = callback;
+  }
+
+  public notifyChange(change: NodeStateChangeEventArgs) {
+    if (!this.callback) {
+      throw new Error('callback is not set');
+    }
+    this.callback(change);
+  }
+
+  public get(): typeof useNodeStateChangeAggregator {
+    return (treeWatcher: WatchSource<TreeRoot>) => {
+      this.treeWatcher = treeWatcher;
+      return {
+        onNodeStateChange: this.onNodeStateChange.bind(this),
+      };
+    };
+  }
+}