diff --git a/src/application/Common/Enum.ts b/src/application/Common/Enum.ts
index 74f42218..81b9384a 100644
--- a/src/application/Common/Enum.ts
+++ b/src/application/Common/Enum.ts
@@ -5,13 +5,13 @@ export type EnumType = number | string;
 export type EnumVariable<T extends EnumType, TEnumValue extends EnumType>
   = { [key in T]: TEnumValue };
 
-export interface IEnumParser<TEnum> {
+export interface EnumParser<TEnum> {
   parseEnum(value: string, propertyName: string): TEnum;
 }
 
 export function createEnumParser<T extends EnumType, TEnumValue extends EnumType>(
   enumVariable: EnumVariable<T, TEnumValue>,
-): IEnumParser<TEnumValue> {
+): EnumParser<TEnumValue> {
   return {
     parseEnum: (value, propertyName) => parseEnumValue(value, propertyName, enumVariable),
   };
diff --git a/src/application/Parser/ApplicationParser.ts b/src/application/Parser/ApplicationParser.ts
index 5a9d0e60..612c5b9d 100644
--- a/src/application/Parser/ApplicationParser.ts
+++ b/src/application/Parser/ApplicationParser.ts
@@ -1,40 +1,48 @@
 import type { CollectionData } from '@/application/collections/';
 import type { IApplication } from '@/domain/IApplication';
-import type { ProjectDetails } from '@/domain/Project/ProjectDetails';
-import type { ICategoryCollection } from '@/domain/ICategoryCollection';
 import WindowsData from '@/application/collections/windows.yaml';
 import MacOsData from '@/application/collections/macos.yaml';
 import LinuxData from '@/application/collections/linux.yaml';
-import { parseProjectDetails } from '@/application/Parser/ProjectDetailsParser';
+import { parseProjectDetails, type ProjectDetailsParser } from '@/application/Parser/ProjectDetailsParser';
 import { Application } from '@/domain/Application';
-import type { IAppMetadata } from '@/infrastructure/EnvironmentVariables/IAppMetadata';
-import { EnvironmentVariablesFactory } from '@/infrastructure/EnvironmentVariables/EnvironmentVariablesFactory';
-import { parseCategoryCollection } from './CategoryCollectionParser';
+import { parseCategoryCollection, type CategoryCollectionParser } from './CategoryCollectionParser';
+import { createTypeValidator, type TypeValidator } from './Common/TypeValidator';
 
 export function parseApplication(
-  categoryParser = parseCategoryCollection,
-  projectDetailsParser = parseProjectDetails,
-  metadata: IAppMetadata = EnvironmentVariablesFactory.Current.instance,
-  collectionsData = PreParsedCollections,
+  collectionsData: readonly CollectionData[] = PreParsedCollections,
+  utilities: ApplicationParserUtilities = DefaultUtilities,
 ): IApplication {
-  validateCollectionsData(collectionsData);
-  const projectDetails = projectDetailsParser(metadata);
+  validateCollectionsData(collectionsData, utilities.validator);
+  const projectDetails = utilities.parseProjectDetails();
   const collections = collectionsData.map(
-    (collection) => categoryParser(collection, projectDetails),
+    (collection) => utilities.parseCategoryCollection(collection, projectDetails),
   );
   const app = new Application(projectDetails, collections);
   return app;
 }
 
-export type CategoryCollectionParserType
-    = (file: CollectionData, projectDetails: ProjectDetails) => ICategoryCollection;
-
-const PreParsedCollections: readonly CollectionData [] = [
+const PreParsedCollections: readonly CollectionData[] = [
   WindowsData, MacOsData, LinuxData,
 ];
 
-function validateCollectionsData(collections: readonly CollectionData[]) {
-  if (!collections.length) {
-    throw new Error('missing collections');
-  }
+function validateCollectionsData(
+  collections: readonly CollectionData[],
+  validator: TypeValidator,
+) {
+  validator.assertNonEmptyCollection({
+    value: collections,
+    valueName: 'collections',
+  });
 }
+
+interface ApplicationParserUtilities {
+  readonly parseCategoryCollection: CategoryCollectionParser;
+  readonly validator: TypeValidator;
+  readonly parseProjectDetails: ProjectDetailsParser;
+}
+
+const DefaultUtilities: ApplicationParserUtilities = {
+  parseCategoryCollection,
+  parseProjectDetails,
+  validator: createTypeValidator(),
+};
diff --git a/src/application/Parser/CategoryCollectionParser.ts b/src/application/Parser/CategoryCollectionParser.ts
index 8aef0a80..7c92c7d3 100644
--- a/src/application/Parser/CategoryCollectionParser.ts
+++ b/src/application/Parser/CategoryCollectionParser.ts
@@ -3,33 +3,73 @@ import { OperatingSystem } from '@/domain/OperatingSystem';
 import type { ICategoryCollection } from '@/domain/ICategoryCollection';
 import { CategoryCollection } from '@/domain/CategoryCollection';
 import type { ProjectDetails } from '@/domain/Project/ProjectDetails';
-import { createEnumParser } from '../Common/Enum';
-import { parseCategory } from './Executable/CategoryParser';
-import { ScriptingDefinitionParser } from './ScriptingDefinition/ScriptingDefinitionParser';
+import { createEnumParser, type EnumParser } from '../Common/Enum';
+import { parseCategory, type CategoryParser } from './Executable/CategoryParser';
+import { parseScriptingDefinition, type ScriptingDefinitionParser } from './ScriptingDefinition/ScriptingDefinitionParser';
+import { createTypeValidator, type TypeValidator } from './Common/TypeValidator';
 import { createCollectionUtilities, type CategoryCollectionSpecificUtilitiesFactory } from './Executable/CategoryCollectionSpecificUtilities';
 
-export function parseCategoryCollection(
-  content: CollectionData,
-  projectDetails: ProjectDetails,
-  osParser = createEnumParser(OperatingSystem),
-  createUtilities: CategoryCollectionSpecificUtilitiesFactory = createCollectionUtilities,
-): ICategoryCollection {
-  validate(content);
-  const scripting = new ScriptingDefinitionParser()
-    .parse(content.scripting, projectDetails);
-  const utilities = createUtilities(content.functions, scripting);
-  const categories = content.actions.map((action) => parseCategory(action, utilities));
-  const os = osParser.parseEnum(content.os, 'os');
-  const collection = new CategoryCollection(
-    os,
-    categories,
-    scripting,
+export const parseCategoryCollection: CategoryCollectionParser = (
+  content,
+  projectDetails,
+  utilities: CategoryCollectionParserUtilities = DefaultUtilities,
+) => {
+  validateCollection(content, utilities.validator);
+  const scripting = utilities.parseScriptingDefinition(content.scripting, projectDetails);
+  const collectionUtilities = utilities.createUtilities(content.functions, scripting);
+  const categories = content.actions.map(
+    (action) => utilities.parseCategory(action, collectionUtilities),
   );
+  const os = utilities.osParser.parseEnum(content.os, 'os');
+  const collection = utilities.createCategoryCollection({
+    os, actions: categories, scripting,
+  });
   return collection;
+};
+
+export type CategoryCollectionFactory = (
+  ...parameters: ConstructorParameters<typeof CategoryCollection>
+) => ICategoryCollection;
+
+export interface CategoryCollectionParser {
+  (
+    content: CollectionData,
+    projectDetails: ProjectDetails,
+    utilities?: CategoryCollectionParserUtilities,
+  ): ICategoryCollection;
 }
 
-function validate(content: CollectionData): void {
-  if (!content.actions.length) {
-    throw new Error('content does not define any action');
-  }
+function validateCollection(
+  content: CollectionData,
+  validator: TypeValidator,
+): void {
+  validator.assertObject({
+    value: content,
+    valueName: 'collection',
+    allowedProperties: [
+      'os', 'scripting', 'actions', 'functions',
+    ],
+  });
+  validator.assertNonEmptyCollection({
+    value: content.actions,
+    valueName: '"actions" in collection',
+  });
 }
+
+interface CategoryCollectionParserUtilities {
+  readonly osParser: EnumParser<OperatingSystem>;
+  readonly validator: TypeValidator;
+  readonly parseScriptingDefinition: ScriptingDefinitionParser;
+  readonly createUtilities: CategoryCollectionSpecificUtilitiesFactory;
+  readonly parseCategory: CategoryParser;
+  readonly createCategoryCollection: CategoryCollectionFactory;
+}
+
+const DefaultUtilities: CategoryCollectionParserUtilities = {
+  osParser: createEnumParser(OperatingSystem),
+  validator: createTypeValidator(),
+  parseScriptingDefinition,
+  createUtilities: createCollectionUtilities,
+  parseCategory,
+  createCategoryCollection: (...args) => new CategoryCollection(...args),
+};
diff --git a/src/application/Parser/ContextualError.ts b/src/application/Parser/Common/ContextualError.ts
similarity index 100%
rename from src/application/Parser/ContextualError.ts
rename to src/application/Parser/Common/ContextualError.ts
diff --git a/src/application/Parser/Common/TypeValidator.ts b/src/application/Parser/Common/TypeValidator.ts
new file mode 100644
index 00000000..05d13efa
--- /dev/null
+++ b/src/application/Parser/Common/TypeValidator.ts
@@ -0,0 +1,96 @@
+import type { PropertyKeys } from '@/TypeHelpers';
+import { isNullOrUndefined, isArray, isPlainObject } from '@/TypeHelpers';
+
+export interface TypeValidator {
+  assertObject<T>(assertion: ObjectAssertion<T>): void;
+  assertNonEmptyCollection(assertion: NonEmptyCollectionAssertion): void;
+}
+
+export interface NonEmptyCollectionAssertion {
+  readonly value: unknown;
+  readonly valueName: string;
+}
+
+export interface ObjectAssertion<T> {
+  readonly value: T | unknown;
+  readonly valueName: string;
+  readonly allowedProperties?: readonly PropertyKeys<T>[];
+}
+
+export function createTypeValidator(): TypeValidator {
+  return {
+    assertObject: (assertion) => {
+      assertDefined(assertion.value, assertion.valueName);
+      assertPlainObject(assertion.value, assertion.valueName);
+      assertNoEmptyProperties(assertion.value, assertion.valueName);
+      if (assertion.allowedProperties !== undefined) {
+        const allowedProperties = assertion.allowedProperties.map((p) => p as string);
+        assertAllowedProperties(assertion.value, assertion.valueName, allowedProperties);
+      }
+    },
+    assertNonEmptyCollection: (assertion) => {
+      assertDefined(assertion.value, assertion.valueName);
+      assertArray(assertion.value, assertion.valueName);
+      assertNonEmpty(assertion.value, assertion.valueName);
+    },
+  };
+}
+
+function assertDefined<T>(
+  value: T,
+  valueName: string,
+): asserts value is NonNullable<T> {
+  if (isNullOrUndefined(value)) {
+    throw new Error(`'${valueName}' is missing.`);
+  }
+}
+
+function assertPlainObject(
+  value: unknown,
+  valueName: string,
+): asserts value is object {
+  if (!isPlainObject(value)) {
+    throw new Error(`'${valueName}' is not an object.`);
+  }
+}
+
+function assertNoEmptyProperties(
+  value: object,
+  valueName: string,
+): void {
+  if (Object.keys(value).length === 0) {
+    throw new Error(`'${valueName}' is an empty object without properties.`);
+  }
+}
+
+function assertAllowedProperties(
+  value: object,
+  valueName: string,
+  allowedProperties: readonly string[],
+): void {
+  const properties = Object.keys(value).map((p) => p as string);
+  const disallowedProperties = properties.filter(
+    (prop) => !allowedProperties.map((p) => p as string).includes(prop),
+  );
+  if (disallowedProperties.length > 0) {
+    throw new Error(`'${valueName}' has disallowed properties: ${disallowedProperties.join(', ')}.`);
+  }
+}
+
+function assertArray(
+  value: unknown,
+  valueName: string,
+): asserts value is Array<unknown> {
+  if (!isArray(value)) {
+    throw new Error(`'${valueName}' should be of type 'array', but is of type '${typeof value}'.`);
+  }
+}
+
+function assertNonEmpty(
+  value: Array<unknown>,
+  valueName: string,
+): void {
+  if (value.length === 0) {
+    throw new Error(`'${valueName}' cannot be an empty array.`);
+  }
+}
diff --git a/src/application/Parser/Executable/CategoryParser.ts b/src/application/Parser/Executable/CategoryParser.ts
index 30dd5eb0..39d77e51 100644
--- a/src/application/Parser/Executable/CategoryParser.ts
+++ b/src/application/Parser/Executable/CategoryParser.ts
@@ -1,7 +1,7 @@
 import type {
   CategoryData, ScriptData, ExecutableData,
 } from '@/application/collections/';
-import { wrapErrorWithAdditionalContext, type ErrorWithContextWrapper } from '@/application/Parser/ContextualError';
+import { wrapErrorWithAdditionalContext, type ErrorWithContextWrapper } from '@/application/Parser/Common/ContextualError';
 import type { Category } from '@/domain/Executables/Category/Category';
 import { CollectionCategory } from '@/domain/Executables/Category/CollectionCategory';
 import type { Script } from '@/domain/Executables/Script/Script';
@@ -13,16 +13,24 @@ import type { CategoryCollectionSpecificUtilities } from './CategoryCollectionSp
 
 let categoryIdCounter = 0;
 
-export function parseCategory(
+export const parseCategory: CategoryParser = (
   category: CategoryData,
   collectionUtilities: CategoryCollectionSpecificUtilities,
   categoryUtilities: CategoryParserUtilities = DefaultCategoryParserUtilities,
-): Category {
+) => {
   return parseCategoryRecursively({
     categoryData: category,
     collectionUtilities,
     categoryUtilities,
   });
+};
+
+export interface CategoryParser {
+  (
+    category: CategoryData,
+    collectionUtilities: CategoryCollectionSpecificUtilities,
+    categoryUtilities?: CategoryParserUtilities,
+  ): Category;
 }
 
 interface CategoryParseContext {
@@ -41,7 +49,7 @@ function parseCategoryRecursively(
     subscripts: new Array<Script>(),
   };
   for (const data of context.categoryData.children) {
-    parseExecutable({
+    parseUnknownExecutable({
       data,
       children,
       parent: context.categoryData,
@@ -74,12 +82,18 @@ function ensureValidCategory(
     self: context.categoryData,
     parentCategory: context.parentCategory,
   });
-  validator.assertDefined(category);
+  validator.assertType((v) => v.assertObject({
+    value: category,
+    valueName: category.category ?? 'category',
+    allowedProperties: [
+      'docs', 'children', 'category',
+    ],
+  }));
   validator.assertValidName(category.category);
-  validator.assert(
-    () => Boolean(category.children) && category.children.length > 0,
-    `"${category.category}" has no children.`,
-  );
+  validator.assertType((v) => v.assertNonEmptyCollection({
+    value: category.children,
+    valueName: category.category,
+  }));
   return validator;
 }
 
@@ -96,12 +110,15 @@ interface ExecutableParseContext {
   readonly categoryUtilities: CategoryParserUtilities;
 }
 
-function parseExecutable(context: ExecutableParseContext) {
+function parseUnknownExecutable(context: ExecutableParseContext) {
   const validator: ExecutableValidator = context.categoryUtilities.createValidator({
     self: context.data,
     parentCategory: context.parent,
   });
-  validator.assertDefined(context.data);
+  validator.assertType((v) => v.assertObject({
+    value: context.data,
+    valueName: 'Executable',
+  }));
   validator.assert(
     () => isCategory(context.data) || isScript(context.data),
     'Executable is neither a category or a script.',
diff --git a/src/application/Parser/Executable/DocumentationParser.ts b/src/application/Parser/Executable/DocumentationParser.ts
index 9ac70fcd..5d01938c 100644
--- a/src/application/Parser/Executable/DocumentationParser.ts
+++ b/src/application/Parser/Executable/DocumentationParser.ts
@@ -50,5 +50,5 @@ class DocumentationContainer {
 }
 
 function throwInvalidType(): never {
-  throw new Error('docs field (documentation) must be an array of strings');
+  throw new Error('docs field (documentation) must be a single string or an array of strings.');
 }
diff --git a/src/application/Parser/Executable/Script/Compiler/Expressions/Parser/Regex/RegexParser.ts b/src/application/Parser/Executable/Script/Compiler/Expressions/Parser/Regex/RegexParser.ts
index 6e8d0e7d..aeaa53c0 100644
--- a/src/application/Parser/Executable/Script/Compiler/Expressions/Parser/Regex/RegexParser.ts
+++ b/src/application/Parser/Executable/Script/Compiler/Expressions/Parser/Regex/RegexParser.ts
@@ -1,4 +1,4 @@
-import { wrapErrorWithAdditionalContext, type ErrorWithContextWrapper } from '@/application/Parser/ContextualError';
+import { wrapErrorWithAdditionalContext, type ErrorWithContextWrapper } from '@/application/Parser/Common/ContextualError';
 import { Expression, type ExpressionEvaluator } from '../../Expression/Expression';
 import { createPositionFromRegexFullMatch, type ExpressionPositionFactory } from '../../Expression/ExpressionPositionFactory';
 import { createFunctionParameterCollection, type FunctionParameterCollectionFactory } from '../../../Function/Parameter/FunctionParameterCollectionFactory';
diff --git a/src/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/SingleCall/Strategies/Argument/NestedFunctionArgumentCompiler.ts b/src/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/SingleCall/Strategies/Argument/NestedFunctionArgumentCompiler.ts
index 92ce998c..f1ba6c04 100644
--- a/src/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/SingleCall/Strategies/Argument/NestedFunctionArgumentCompiler.ts
+++ b/src/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/SingleCall/Strategies/Argument/NestedFunctionArgumentCompiler.ts
@@ -6,7 +6,7 @@ import type { IExpressionsCompiler } from '@/application/Parser/Executable/Scrip
 import type { FunctionCall } from '@/application/Parser/Executable/Script/Compiler/Function/Call/FunctionCall';
 import type { FunctionCallCompilationContext } from '@/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/FunctionCallCompilationContext';
 import { ParsedFunctionCall } from '@/application/Parser/Executable/Script/Compiler/Function/Call/ParsedFunctionCall';
-import { wrapErrorWithAdditionalContext, type ErrorWithContextWrapper } from '@/application/Parser/ContextualError';
+import { wrapErrorWithAdditionalContext, type ErrorWithContextWrapper } from '@/application/Parser/Common/ContextualError';
 import type { ArgumentCompiler } from './ArgumentCompiler';
 
 export class NestedFunctionArgumentCompiler implements ArgumentCompiler {
diff --git a/src/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/SingleCall/Strategies/NestedFunctionCallCompiler.ts b/src/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/SingleCall/Strategies/NestedFunctionCallCompiler.ts
index fd57418a..e9c9e2a6 100644
--- a/src/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/SingleCall/Strategies/NestedFunctionCallCompiler.ts
+++ b/src/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/SingleCall/Strategies/NestedFunctionCallCompiler.ts
@@ -5,7 +5,7 @@ import {
 import type { FunctionCall } from '@/application/Parser/Executable/Script/Compiler/Function/Call/FunctionCall';
 import type { FunctionCallCompilationContext } from '@/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/FunctionCallCompilationContext';
 import type { CompiledCode } from '@/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/CompiledCode';
-import { wrapErrorWithAdditionalContext, type ErrorWithContextWrapper } from '@/application/Parser/ContextualError';
+import { wrapErrorWithAdditionalContext, type ErrorWithContextWrapper } from '@/application/Parser/Common/ContextualError';
 import { NestedFunctionArgumentCompiler } from './Argument/NestedFunctionArgumentCompiler';
 import type { SingleCallCompilerStrategy } from '../SingleCallCompilerStrategy';
 import type { ArgumentCompiler } from './Argument/ArgumentCompiler';
diff --git a/src/application/Parser/Executable/Script/Compiler/Function/SharedFunctionsParser.ts b/src/application/Parser/Executable/Script/Compiler/Function/SharedFunctionsParser.ts
index a322fc64..f7d7f22e 100644
--- a/src/application/Parser/Executable/Script/Compiler/Function/SharedFunctionsParser.ts
+++ b/src/application/Parser/Executable/Script/Compiler/Function/SharedFunctionsParser.ts
@@ -8,7 +8,7 @@ import { NoEmptyLines } from '@/application/Parser/Executable/Script/Validation/
 import { NoDuplicatedLines } from '@/application/Parser/Executable/Script/Validation/Rules/NoDuplicatedLines';
 import type { ICodeValidator } from '@/application/Parser/Executable/Script/Validation/ICodeValidator';
 import { isArray, isNullOrUndefined, isPlainObject } from '@/TypeHelpers';
-import { wrapErrorWithAdditionalContext, type ErrorWithContextWrapper } from '@/application/Parser/ContextualError';
+import { wrapErrorWithAdditionalContext, type ErrorWithContextWrapper } from '@/application/Parser/Common/ContextualError';
 import { createFunctionWithInlineCode, createCallerFunction } from './SharedFunction';
 import { SharedFunctionCollection } from './SharedFunctionCollection';
 import { FunctionParameter } from './Parameter/FunctionParameter';
diff --git a/src/application/Parser/Executable/Script/Compiler/ScriptCompiler.ts b/src/application/Parser/Executable/Script/Compiler/ScriptCompiler.ts
index 02271774..68cf1fd0 100644
--- a/src/application/Parser/Executable/Script/Compiler/ScriptCompiler.ts
+++ b/src/application/Parser/Executable/Script/Compiler/ScriptCompiler.ts
@@ -4,7 +4,7 @@ import type { ILanguageSyntax } from '@/application/Parser/Executable/Script/Val
 import { CodeValidator } from '@/application/Parser/Executable/Script/Validation/CodeValidator';
 import { NoEmptyLines } from '@/application/Parser/Executable/Script/Validation/Rules/NoEmptyLines';
 import type { ICodeValidator } from '@/application/Parser/Executable/Script/Validation/ICodeValidator';
-import { wrapErrorWithAdditionalContext, type ErrorWithContextWrapper } from '@/application/Parser/ContextualError';
+import { wrapErrorWithAdditionalContext, type ErrorWithContextWrapper } from '@/application/Parser/Common/ContextualError';
 import { createScriptCode, type ScriptCodeFactory } from '@/domain/Executables/Script/Code/ScriptCodeFactory';
 import { SharedFunctionsParser } from './Function/SharedFunctionsParser';
 import { FunctionCallSequenceCompiler } from './Function/Call/Compiler/FunctionCallSequenceCompiler';
diff --git a/src/application/Parser/Executable/Script/ScriptParser.ts b/src/application/Parser/Executable/Script/ScriptParser.ts
index cc346622..e248bde1 100644
--- a/src/application/Parser/Executable/Script/ScriptParser.ts
+++ b/src/application/Parser/Executable/Script/ScriptParser.ts
@@ -5,11 +5,11 @@ import { CollectionScript } from '@/domain/Executables/Script/CollectionScript';
 import { RecommendationLevel } from '@/domain/Executables/Script/RecommendationLevel';
 import type { ScriptCode } from '@/domain/Executables/Script/Code/ScriptCode';
 import type { ICodeValidator } from '@/application/Parser/Executable/Script/Validation/ICodeValidator';
-import { wrapErrorWithAdditionalContext, type ErrorWithContextWrapper } from '@/application/Parser/ContextualError';
+import { wrapErrorWithAdditionalContext, type ErrorWithContextWrapper } from '@/application/Parser/Common/ContextualError';
 import type { ScriptCodeFactory } from '@/domain/Executables/Script/Code/ScriptCodeFactory';
 import { createScriptCode } from '@/domain/Executables/Script/Code/ScriptCodeFactory';
 import type { Script } from '@/domain/Executables/Script/Script';
-import { createEnumParser, type IEnumParser } from '@/application/Common/Enum';
+import { createEnumParser, type EnumParser } from '@/application/Common/Enum';
 import { parseDocs, type DocsParser } from '../DocumentationParser';
 import { ExecutableType } from '../Validation/ExecutableType';
 import { createExecutableDataValidator, type ExecutableValidator, type ExecutableValidatorFactory } from '../Validation/ExecutableValidator';
@@ -28,23 +28,28 @@ export interface ScriptParser {
 export const parseScript: ScriptParser = (
   data,
   collectionUtilities,
-  utilities = DefaultScriptParserUtilities,
+  scriptUtilities = DefaultUtilities,
 ) => {
-  const validator = utilities.createValidator({
+  const validator = scriptUtilities.createValidator({
     type: ExecutableType.Script,
     self: data,
   });
   validateScript(data, validator);
   try {
-    const script = utilities.createScript({
+    const script = scriptUtilities.createScript({
       name: data.name,
-      code: parseCode(data, collectionUtilities, utilities.codeValidator, utilities.createCode),
-      docs: utilities.parseDocs(data),
-      level: parseLevel(data.recommend, utilities.levelParser),
+      code: parseCode(
+        data,
+        collectionUtilities,
+        scriptUtilities.codeValidator,
+        scriptUtilities.createCode,
+      ),
+      docs: scriptUtilities.parseDocs(data),
+      level: parseLevel(data.recommend, scriptUtilities.levelParser),
     });
     return script;
   } catch (error) {
-    throw utilities.wrapError(
+    throw scriptUtilities.wrapError(
       error,
       validator.createContextualErrorMessage('Failed to parse script.'),
     );
@@ -53,7 +58,7 @@ export const parseScript: ScriptParser = (
 
 function parseLevel(
   level: string | undefined,
-  parser: IEnumParser<RecommendationLevel>,
+  parser: EnumParser<RecommendationLevel>,
 ): RecommendationLevel | undefined {
   if (!level) {
     return undefined;
@@ -95,7 +100,13 @@ function validateScript(
   script: ScriptData,
   validator: ExecutableValidator,
 ): asserts script is NonNullable<ScriptData> {
-  validator.assertDefined(script);
+  validator.assertType((v) => v.assertObject<CallScriptData & CodeScriptData>({
+    value: script,
+    valueName: script.name ?? 'script',
+    allowedProperties: [
+      'name', 'recommend', 'code', 'revertCode', 'call', 'docs',
+    ],
+  }));
   validator.assertValidName(script.name);
   validator.assert(
     () => Boolean((script as CodeScriptData).code || (script as CallScriptData).call),
@@ -112,7 +123,7 @@ function validateScript(
 }
 
 interface ScriptParserUtilities {
-  readonly levelParser: IEnumParser<RecommendationLevel>;
+  readonly levelParser: EnumParser<RecommendationLevel>;
   readonly createScript: ScriptFactory;
   readonly codeValidator: ICodeValidator;
   readonly wrapError: ErrorWithContextWrapper;
@@ -129,7 +140,7 @@ const createScript: ScriptFactory = (...parameters) => {
   return new CollectionScript(...parameters);
 };
 
-const DefaultScriptParserUtilities: ScriptParserUtilities = {
+const DefaultUtilities: ScriptParserUtilities = {
   levelParser: createEnumParser(RecommendationLevel),
   createScript,
   codeValidator: CodeValidator.instance,
diff --git a/src/application/Parser/Executable/Validation/ExecutableValidator.ts b/src/application/Parser/Executable/Validation/ExecutableValidator.ts
index c69f8afc..a5c96901 100644
--- a/src/application/Parser/Executable/Validation/ExecutableValidator.ts
+++ b/src/application/Parser/Executable/Validation/ExecutableValidator.ts
@@ -1,5 +1,5 @@
 import { isString } from '@/TypeHelpers';
-import type { ExecutableData } from '@/application/collections/';
+import { createTypeValidator, type TypeValidator } from '../../Common/TypeValidator';
 import { type ExecutableErrorContext } from './ExecutableErrorContext';
 import { createExecutableContextErrorMessage, type ExecutableContextErrorMessageCreator } from './ExecutableErrorContextMessage';
 
@@ -7,11 +7,11 @@ export interface ExecutableValidatorFactory {
   (context: ExecutableErrorContext): ExecutableValidator;
 }
 
+type AssertTypeFunction = (validator: TypeValidator) => void;
+
 export interface ExecutableValidator {
   assertValidName(nameValue: string): void;
-  assertDefined(
-    data: ExecutableData | undefined,
-  ): asserts data is NonNullable<ExecutableData> & void;
+  assertType(assert: AssertTypeFunction): void;
   assert(
     validationPredicate: () => boolean,
     errorMessage: string,
@@ -27,6 +27,7 @@ export class ContextualExecutableValidator implements ExecutableValidator {
     private readonly context: ExecutableErrorContext,
     private readonly createErrorMessage
     : ExecutableContextErrorMessageCreator = createExecutableContextErrorMessage,
+    private readonly validator: TypeValidator = createTypeValidator(),
   ) {
 
   }
@@ -39,13 +40,12 @@ export class ContextualExecutableValidator implements ExecutableValidator {
     );
   }
 
-  public assertDefined(
-    data: ExecutableData,
-  ): asserts data is NonNullable<ExecutableData> {
-    this.assert(
-      () => data !== undefined && data !== null && Object.keys(data).length > 0,
-      'missing executable data',
-    );
+  public assertType(assert: AssertTypeFunction): void {
+    try {
+      assert(this.validator);
+    } catch (error) {
+      this.throw(error.message);
+    }
   }
 
   public assert(
diff --git a/src/application/Parser/ProjectDetailsParser.ts b/src/application/Parser/ProjectDetailsParser.ts
index 7aa1fd55..97749b4e 100644
--- a/src/application/Parser/ProjectDetailsParser.ts
+++ b/src/application/Parser/ProjectDetailsParser.ts
@@ -24,6 +24,10 @@ parseProjectDetails(
   );
 }
 
+export interface ProjectDetailsParser {
+  (): ProjectDetails;
+}
+
 export type ProjectDetailsFactory = (
   ...args: ConstructorArguments<typeof GitHubProjectDetails>
 ) => ProjectDetails;
diff --git a/src/application/Parser/ScriptingDefinition/ScriptingDefinitionParser.ts b/src/application/Parser/ScriptingDefinition/ScriptingDefinitionParser.ts
index e8fb465b..49ccf9f6 100644
--- a/src/application/Parser/ScriptingDefinition/ScriptingDefinitionParser.ts
+++ b/src/application/Parser/ScriptingDefinition/ScriptingDefinitionParser.ts
@@ -3,28 +3,54 @@ import type { IScriptingDefinition } from '@/domain/IScriptingDefinition';
 import { ScriptingDefinition } from '@/domain/ScriptingDefinition';
 import { ScriptingLanguage } from '@/domain/ScriptingLanguage';
 import type { ProjectDetails } from '@/domain/Project/ProjectDetails';
-import { createEnumParser } from '../../Common/Enum';
+import { createEnumParser, type EnumParser } from '../../Common/Enum';
+import { createTypeValidator, type TypeValidator } from '../Common/TypeValidator';
 import { CodeSubstituter } from './CodeSubstituter';
 import type { ICodeSubstituter } from './ICodeSubstituter';
 
-export class ScriptingDefinitionParser {
-  constructor(
-    private readonly languageParser = createEnumParser(ScriptingLanguage),
-    private readonly codeSubstituter: ICodeSubstituter = new CodeSubstituter(),
-  ) {
-  }
+export const parseScriptingDefinition: ScriptingDefinitionParser = (
+  definition,
+  projectDetails,
+  utilities: ScriptingDefinitionParserUtilities = DefaultUtilities,
+) => {
+  validateData(definition, utilities.validator);
+  const language = utilities.languageParser.parseEnum(definition.language, 'language');
+  const startCode = utilities.codeSubstituter.substitute(definition.startCode, projectDetails);
+  const endCode = utilities.codeSubstituter.substitute(definition.endCode, projectDetails);
+  return new ScriptingDefinition(
+    language,
+    startCode,
+    endCode,
+  );
+};
 
-  public parse(
+export interface ScriptingDefinitionParser {
+  (
     definition: ScriptingDefinitionData,
     projectDetails: ProjectDetails,
-  ): IScriptingDefinition {
-    const language = this.languageParser.parseEnum(definition.language, 'language');
-    const startCode = this.codeSubstituter.substitute(definition.startCode, projectDetails);
-    const endCode = this.codeSubstituter.substitute(definition.endCode, projectDetails);
-    return new ScriptingDefinition(
-      language,
-      startCode,
-      endCode,
-    );
-  }
+    utilities?: ScriptingDefinitionParserUtilities,
+  ): IScriptingDefinition;
 }
+
+function validateData(
+  data: ScriptingDefinitionData,
+  validator: TypeValidator,
+): void {
+  validator.assertObject({
+    value: data,
+    valueName: 'scripting definition',
+    allowedProperties: ['language', 'fileExtension', 'startCode', 'endCode'],
+  });
+}
+
+interface ScriptingDefinitionParserUtilities {
+  readonly languageParser: EnumParser<ScriptingLanguage>;
+  readonly codeSubstituter: ICodeSubstituter;
+  readonly validator: TypeValidator;
+}
+
+const DefaultUtilities: ScriptingDefinitionParserUtilities = {
+  languageParser: createEnumParser(ScriptingLanguage),
+  codeSubstituter: new CodeSubstituter(),
+  validator: createTypeValidator(),
+};
diff --git a/src/domain/CategoryCollection.ts b/src/domain/CategoryCollection.ts
index 6ce9580d..71d8c61e 100644
--- a/src/domain/CategoryCollection.ts
+++ b/src/domain/CategoryCollection.ts
@@ -8,19 +8,27 @@ import type { IScriptingDefinition } from './IScriptingDefinition';
 import type { ICategoryCollection } from './ICategoryCollection';
 
 export class CategoryCollection implements ICategoryCollection {
+  public readonly os: OperatingSystem;
+
+  public readonly actions: ReadonlyArray<Category>;
+
+  public readonly scripting: IScriptingDefinition;
+
   public get totalScripts(): number { return this.queryable.allScripts.length; }
 
   public get totalCategories(): number { return this.queryable.allCategories.length; }
 
-  private readonly queryable: IQueryableCollection;
+  private readonly queryable: QueryableCollection;
 
   constructor(
-    public readonly os: OperatingSystem,
-    public readonly actions: ReadonlyArray<Category>,
-    public readonly scripting: IScriptingDefinition,
+    parameters: CategoryCollectionInitParameters,
   ) {
-    this.queryable = makeQueryable(actions);
-    assertInRange(os, OperatingSystem);
+    this.os = parameters.os;
+    this.actions = parameters.actions;
+    this.scripting = parameters.scripting;
+
+    this.queryable = makeQueryable(this.actions);
+    assertInRange(this.os, OperatingSystem);
     ensureValid(this.queryable);
     ensureNoDuplicates(this.queryable.allCategories);
     ensureNoDuplicates(this.queryable.allScripts);
@@ -72,13 +80,19 @@ function ensureNoDuplicates<TKey>(entities: ReadonlyArray<IEntity<TKey>>) {
   }
 }
 
-interface IQueryableCollection {
-  allCategories: Category[];
-  allScripts: Script[];
-  scriptsByLevel: Map<RecommendationLevel, readonly Script[]>;
+export interface CategoryCollectionInitParameters {
+  readonly os: OperatingSystem;
+  readonly actions: ReadonlyArray<Category>;
+  readonly scripting: IScriptingDefinition;
 }
 
-function ensureValid(application: IQueryableCollection) {
+interface QueryableCollection {
+  readonly allCategories: Category[];
+  readonly allScripts: Script[];
+  readonly scriptsByLevel: Map<RecommendationLevel, readonly Script[]>;
+}
+
+function ensureValid(application: QueryableCollection) {
   ensureValidCategories(application.allCategories);
   ensureValidScripts(application.allScripts);
 }
@@ -128,7 +142,7 @@ function flattenApplication(
 
 function makeQueryable(
   actions: ReadonlyArray<Category>,
-): IQueryableCollection {
+): QueryableCollection {
   const flattened = flattenApplication(actions);
   return {
     allCategories: flattened[0],
diff --git a/tests/shared/Assertions/ExpectDeepIncludes.ts b/tests/shared/Assertions/ExpectDeepIncludes.ts
new file mode 100644
index 00000000..f67774fc
--- /dev/null
+++ b/tests/shared/Assertions/ExpectDeepIncludes.ts
@@ -0,0 +1,47 @@
+import { formatAssertionMessage } from '@tests/shared/FormatAssertionMessage';
+import { indentText } from '@tests/shared/Text';
+
+/**
+ * Asserts that an array deeply includes a specified item by comparing JSON-serialized versions.
+ * Designed to be used as the Chai methods 'to.deep.include' and 'to.deep.contain' do not work.
+ */
+export function expectDeepIncludes<T>(
+  arrayToSearch: readonly T[],
+  expectedItem: T,
+) {
+  const serializedItemsFromArray = arrayToSearch.map((c) => jsonSerializeForComparison(c));
+  const serializedExpectedItem = jsonSerializeForComparison(expectedItem);
+  expect(serializedItemsFromArray).to.include(serializedExpectedItem, formatAssertionMessage([
+    'Mismatch in expected items.',
+    'The provided array does not include the expected item.',
+    'Expected item:',
+    indentText(serializeItemForDisplay(expectedItem)),
+    `Provided items (total: ${arrayToSearch.length}):`,
+    indentText(serializeArrayForDisplay(arrayToSearch)),
+  ]));
+}
+
+function jsonSerializeForComparison(obj: unknown): string {
+  return JSON.stringify(obj);
+}
+
+function serializeArrayForDisplay<T>(array: readonly T[]): string {
+  return array.map((item) => indentText(serializeItemForDisplay(item))).join('\n-\n');
+}
+
+function serializeItemForDisplay(item: unknown): string {
+  const typeDescription = getTypeDescription(item);
+  const jsonSerializedItem = JSON.stringify(item, null, 2);
+  return `${typeDescription}\n${jsonSerializedItem}`;
+}
+
+function getTypeDescription(item: unknown): string {
+  // Basic type detection using typeof
+  let type = typeof item;
+  // More specific type detection for object types using Object.prototype.toString
+  if (type === 'object') {
+    const preciseType = Object.prototype.toString.call(item);
+    type = preciseType.replace(/^\[object (\S+)\]$/, '$1');
+  }
+  return `Type: ${type}`;
+}
diff --git a/tests/unit/application/Parser/ApplicationParser.spec.ts b/tests/unit/application/Parser/ApplicationParser.spec.ts
index 0057444b..b5ad234e 100644
--- a/tests/unit/application/Parser/ApplicationParser.spec.ts
+++ b/tests/unit/application/Parser/ApplicationParser.spec.ts
@@ -1,20 +1,20 @@
 import { describe, it, expect } from 'vitest';
 import type { CollectionData } from '@/application/collections/';
 import { parseProjectDetails } from '@/application/Parser/ProjectDetailsParser';
-import { type CategoryCollectionParserType, parseApplication } from '@/application/Parser/ApplicationParser';
-import type { IAppMetadata } from '@/infrastructure/EnvironmentVariables/IAppMetadata';
+import { parseApplication } from '@/application/Parser/ApplicationParser';
 import WindowsData from '@/application/collections/windows.yaml';
 import MacOsData from '@/application/collections/macos.yaml';
 import LinuxData from '@/application/collections/linux.yaml';
 import { OperatingSystem } from '@/domain/OperatingSystem';
 import { CategoryCollectionStub } from '@tests/unit/shared/Stubs/CategoryCollectionStub';
 import { CollectionDataStub } from '@tests/unit/shared/Stubs/CollectionDataStub';
-import { getAbsentCollectionTestCases } from '@tests/unit/shared/TestCases/AbsentTests';
-import { AppMetadataStub } from '@tests/unit/shared/Stubs/AppMetadataStub';
-import { EnvironmentVariablesFactory } from '@/infrastructure/EnvironmentVariables/EnvironmentVariablesFactory';
 import { CategoryCollectionParserStub } from '@tests/unit/shared/Stubs/CategoryCollectionParserStub';
 import { ProjectDetailsParserStub } from '@tests/unit/shared/Stubs/ProjectDetailsParserStub';
 import { ProjectDetailsStub } from '@tests/unit/shared/Stubs/ProjectDetailsStub';
+import type { CategoryCollectionParser } from '@/application/Parser/CategoryCollectionParser';
+import type { NonEmptyCollectionAssertion, TypeValidator } from '@/application/Parser/Common/TypeValidator';
+import { TypeValidatorStub } from '@tests/unit/shared/Stubs/TypeValidatorStub';
+import type { ICategoryCollection } from '@/domain/ICategoryCollection';
 
 describe('ApplicationParser', () => {
   describe('parseApplication', () => {
@@ -71,45 +71,21 @@ describe('ApplicationParser', () => {
         )).to.equal(true);
       });
     });
-    describe('metadata', () => {
-      it('used to parse expected metadata', () => {
-        // arrange
-        const expectedMetadata = new AppMetadataStub();
-        const projectDetailsParser = new ProjectDetailsParserStub();
-        // act
-        new ApplicationParserBuilder()
-          .withMetadata(expectedMetadata)
-          .withProjectDetailsParser(projectDetailsParser.getStub())
-          .parseApplication();
-        // assert
-        expect(projectDetailsParser.arguments).to.have.lengthOf(1);
-        expect(projectDetailsParser.arguments[0]).to.equal(expectedMetadata);
-      });
-      it('defaults to metadata from factory', () => {
-        // arrange
-        const expectedMetadata: IAppMetadata = EnvironmentVariablesFactory.Current.instance;
-        const projectDetailsParser = new ProjectDetailsParserStub();
-        // act
-        new ApplicationParserBuilder()
-          .withMetadata(undefined) // force using default
-          .withProjectDetailsParser(projectDetailsParser.getStub())
-          .parseApplication();
-        // assert
-        expect(projectDetailsParser.arguments).to.have.lengthOf(1);
-        expect(projectDetailsParser.arguments[0]).to.equal(expectedMetadata);
-      });
-    });
     describe('collectionsData', () => {
       describe('set as expected', () => {
         // arrange
-        const testCases = [
+        const testScenarios: {
+          readonly description: string;
+          readonly input: readonly CollectionData[];
+          readonly output: readonly ICategoryCollection[];
+        }[] = [
           {
-            name: 'single collection',
+            description: 'single collection',
             input: [new CollectionDataStub()],
             output: [new CategoryCollectionStub().withOs(OperatingSystem.macOS)],
           },
           {
-            name: 'multiple collections',
+            description: 'multiple collections',
             input: [
               new CollectionDataStub().withOs('windows'),
               new CollectionDataStub().withOs('macos'),
@@ -121,22 +97,24 @@ describe('ApplicationParser', () => {
           },
         ];
         // act
-        for (const testCase of testCases) {
-          it(testCase.name, () => {
+        testScenarios.forEach(({
+          description, input, output,
+        }) => {
+          it(description, () => {
             let categoryParserStub = new CategoryCollectionParserStub();
-            for (let i = 0; i < testCase.input.length; i++) {
+            for (let i = 0; i < input.length; i++) {
               categoryParserStub = categoryParserStub
-                .withReturnValue(testCase.input[i], testCase.output[i]);
+                .withReturnValue(input[i], output[i]);
             }
             const sut = new ApplicationParserBuilder()
               .withCategoryCollectionParser(categoryParserStub.getStub())
-              .withCollectionsData(testCase.input);
+              .withCollectionsData(input);
             // act
             const app = sut.parseApplication();
             // assert
-            expect(app.collections).to.deep.equal(testCase.output);
+            expect(app.collections).to.deep.equal(output);
           });
-        }
+        });
       });
       it('defaults to expected data', () => {
         // arrange
@@ -151,30 +129,21 @@ describe('ApplicationParser', () => {
         const actual = categoryParserStub.arguments.map((args) => args.data);
         expect(actual).to.deep.equal(expected);
       });
-      describe('throws when data is invalid', () => {
+      it('validates non empty array', () => {
         // arrange
-        const testCases = [
-          ...getAbsentCollectionTestCases<CollectionData>(
-            {
-              excludeUndefined: true,
-              excludeNull: true,
-            },
-          ).map((testCase) => ({
-            name: `given absent collection "${testCase.valueName}"`,
-            value: testCase.absentValue,
-            expectedError: 'missing collections',
-          })),
-        ];
-        for (const testCase of testCases) {
-          it(testCase.name, () => {
-            const sut = new ApplicationParserBuilder()
-              .withCollectionsData(testCase.value);
-            // act
-            const act = () => sut.parseApplication();
-            // assert
-            expect(act).to.throw(testCase.expectedError);
-          });
-        }
+        const data = [new CollectionDataStub()];
+        const expectedAssertion: NonEmptyCollectionAssertion = {
+          value: data,
+          valueName: 'collections',
+        };
+        const validator = new TypeValidatorStub();
+        const sut = new ApplicationParserBuilder()
+          .withCollectionsData(data)
+          .withTypeValidator(validator);
+        // act
+        sut.parseApplication();
+        // assert
+        validator.expectNonEmptyCollectionAssertion(expectedAssertion);
       });
     });
   });
@@ -182,17 +151,17 @@ describe('ApplicationParser', () => {
 
 class ApplicationParserBuilder {
   private categoryCollectionParser
-  : CategoryCollectionParserType = new CategoryCollectionParserStub().getStub();
+  : CategoryCollectionParser = new CategoryCollectionParserStub().getStub();
 
   private projectDetailsParser
   : typeof parseProjectDetails = new ProjectDetailsParserStub().getStub();
 
-  private metadata: IAppMetadata | undefined = new AppMetadataStub();
+  private validator: TypeValidator = new TypeValidatorStub();
 
-  private collectionsData: CollectionData[] | undefined = [new CollectionDataStub()];
+  private collectionsData: readonly CollectionData[] | undefined = [new CollectionDataStub()];
 
   public withCategoryCollectionParser(
-    categoryCollectionParser: CategoryCollectionParserType,
+    categoryCollectionParser: CategoryCollectionParser,
   ): this {
     this.categoryCollectionParser = categoryCollectionParser;
     return this;
@@ -205,24 +174,24 @@ class ApplicationParserBuilder {
     return this;
   }
 
-  public withMetadata(
-    metadata: IAppMetadata | undefined,
-  ): this {
-    this.metadata = metadata;
+  public withCollectionsData(collectionsData: readonly CollectionData[] | undefined): this {
+    this.collectionsData = collectionsData;
     return this;
   }
 
-  public withCollectionsData(collectionsData: CollectionData[] | undefined): this {
-    this.collectionsData = collectionsData;
+  public withTypeValidator(validator: TypeValidator): this {
+    this.validator = validator;
     return this;
   }
 
   public parseApplication(): ReturnType<typeof parseApplication> {
     return parseApplication(
-      this.categoryCollectionParser,
-      this.projectDetailsParser,
-      this.metadata,
       this.collectionsData,
+      {
+        parseCategoryCollection: this.categoryCollectionParser,
+        parseProjectDetails: this.projectDetailsParser,
+        validator: this.validator,
+      },
     );
   }
 }
diff --git a/tests/unit/application/Parser/CategoryCollectionParser.spec.ts b/tests/unit/application/Parser/CategoryCollectionParser.spec.ts
index cec0dae2..c58419e2 100644
--- a/tests/unit/application/Parser/CategoryCollectionParser.spec.ts
+++ b/tests/unit/application/Parser/CategoryCollectionParser.spec.ts
@@ -1,119 +1,313 @@
 import { describe, it, expect } from 'vitest';
-import type { IEntity } from '@/infrastructure/Entity/IEntity';
-import { parseCategoryCollection } from '@/application/Parser/CategoryCollectionParser';
-import { parseCategory } from '@/application/Parser/Executable/CategoryParser';
+import { TypeValidatorStub } from '@tests/unit/shared/Stubs/TypeValidatorStub';
+import { parseCategoryCollection, type CategoryCollectionFactory } from '@/application/Parser/CategoryCollectionParser';
+import { type CategoryParser } from '@/application/Parser/Executable/CategoryParser';
 import { OperatingSystem } from '@/domain/OperatingSystem';
-import { RecommendationLevel } from '@/domain/Executables/Script/RecommendationLevel';
-import { ScriptingDefinitionParser } from '@/application/Parser/ScriptingDefinition/ScriptingDefinitionParser';
 import { EnumParserStub } from '@tests/unit/shared/Stubs/EnumParserStub';
 import { ProjectDetailsStub } from '@tests/unit/shared/Stubs/ProjectDetailsStub';
 import { getCategoryStub, CollectionDataStub } from '@tests/unit/shared/Stubs/CollectionDataStub';
 import { CategoryCollectionSpecificUtilitiesStub } from '@tests/unit/shared/Stubs/CategoryCollectionSpecificUtilitiesStub';
-import { CategoryDataStub } from '@tests/unit/shared/Stubs/CategoryDataStub';
-import { createScriptDataWithCall, createScriptDataWithCode } from '@tests/unit/shared/Stubs/ScriptDataStub';
 import { createFunctionDataWithCode } from '@tests/unit/shared/Stubs/FunctionDataStub';
-import { FunctionCallDataStub } from '@tests/unit/shared/Stubs/FunctionCallDataStub';
-import { itEachAbsentCollectionValue } from '@tests/unit/shared/TestCases/AbsentTests';
-import type { CategoryData } from '@/application/collections/';
+import type { CollectionData, ScriptingDefinitionData, FunctionData } from '@/application/collections/';
+import type { ProjectDetails } from '@/domain/Project/ProjectDetails';
+import type { NonEmptyCollectionAssertion, ObjectAssertion, TypeValidator } from '@/application/Parser/Common/TypeValidator';
+import type { EnumParser } from '@/application/Common/Enum';
+import type { ScriptingDefinitionParser } from '@/application/Parser/ScriptingDefinition/ScriptingDefinitionParser';
+import { ScriptingDefinitionStub } from '@tests/unit/shared/Stubs/ScriptingDefinitionStub';
+import type { CategoryCollectionSpecificUtilitiesFactory } from '@/application/Parser/Executable/CategoryCollectionSpecificUtilities';
+import { ScriptingDefinitionDataStub } from '@tests/unit/shared/Stubs/ScriptingDefinitionDataStub';
+import { CategoryParserStub } from '@tests/unit/shared/Stubs/CategoryParserStub';
+import { createCategoryCollectionFactorySpy } from '@tests/unit/shared/Stubs/CategoryCollectionFactoryStub';
+import { CategoryStub } from '@tests/unit/shared/Stubs/CategoryStub';
+import type { IScriptingDefinition } from '@/domain/IScriptingDefinition';
 
 describe('CategoryCollectionParser', () => {
   describe('parseCategoryCollection', () => {
+    it('validates object', () => {
+      // arrange
+      const data = new CollectionDataStub();
+      const expectedAssertion: ObjectAssertion<CollectionData> = {
+        value: data,
+        valueName: 'collection',
+        allowedProperties: [
+          'os', 'scripting', 'actions', 'functions',
+        ],
+      };
+      const validator = new TypeValidatorStub();
+      const context = new TestContext()
+        .withData(data)
+        .withTypeValidator(validator);
+      // act
+      context.parseCategoryCollection();
+      // assert
+      validator.expectObjectAssertion(expectedAssertion);
+    });
     describe('actions', () => {
-      describe('throws with absent actions', () => {
-        itEachAbsentCollectionValue<CategoryData>((absentValue) => {
-          // arrange
-          const expectedError = 'content does not define any action';
-          const collection = new CollectionDataStub()
-            .withActions(absentValue);
-          const projectDetails = new ProjectDetailsStub();
-          // act
-          const act = () => parseCategoryCollection(collection, projectDetails);
-          // assert
-          expect(act).to.throw(expectedError);
-        }, { excludeUndefined: true, excludeNull: true });
-      });
-      it('parses actions', () => {
+      it('validates non-empty collection', () => {
         // arrange
         const actions = [getCategoryStub('test1'), getCategoryStub('test2')];
-        const context = new CategoryCollectionSpecificUtilitiesStub();
-        const expected = [parseCategory(actions[0], context), parseCategory(actions[1], context)];
-        const collection = new CollectionDataStub()
-          .withActions(actions);
-        const projectDetails = new ProjectDetailsStub();
+        const expectedAssertion: NonEmptyCollectionAssertion = {
+          value: actions,
+          valueName: '"actions" in collection',
+        };
+        const validator = new TypeValidatorStub();
+        const context = new TestContext()
+          .withData(new CollectionDataStub().withActions(actions))
+          .withTypeValidator(validator);
         // act
-        const actual = parseCategoryCollection(collection, projectDetails).actions;
+        context.parseCategoryCollection();
         // assert
-        expect(excludingId(actual)).to.be.deep.equal(excludingId(expected));
-        function excludingId<TId>(array: ReadonlyArray<IEntity<TId>>) {
-          return array.map((obj) => {
-            // eslint-disable-next-line @typescript-eslint/no-unused-vars
-            const { id: omitted, ...rest } = obj;
-            return rest;
+        validator.expectNonEmptyCollectionAssertion(expectedAssertion);
+      });
+      it('parses actions correctly', () => {
+        // arrange
+        const {
+          categoryCollectionFactorySpy,
+          getInitParameters,
+        } = createCategoryCollectionFactorySpy();
+        const actionsData = [getCategoryStub('test1'), getCategoryStub('test2')];
+        const expectedActions = [new CategoryStub(1), new CategoryStub(2)];
+        const categoryParserStub = new CategoryParserStub()
+          .withConfiguredParseResult(actionsData[0], expectedActions[0])
+          .withConfiguredParseResult(actionsData[1], expectedActions[1]);
+        const collectionData = new CollectionDataStub()
+          .withActions(actionsData);
+        const context = new TestContext()
+          .withData(collectionData)
+          .withCategoryParser(categoryParserStub.get())
+          .withCategoryCollectionFactory(categoryCollectionFactorySpy);
+        // act
+        const actualCollection = context.parseCategoryCollection();
+        // assert
+        const actualActions = getInitParameters(actualCollection)?.actions;
+        expect(actualActions).to.have.lengthOf(expectedActions.length);
+        expect(actualActions).to.have.members(expectedActions);
+      });
+      describe('utilities', () => {
+        it('parses actions with correct utilities', () => {
+          // arrange
+          const expectedUtilities = new CategoryCollectionSpecificUtilitiesStub();
+          const utilitiesFactory: CategoryCollectionSpecificUtilitiesFactory = () => {
+            return expectedUtilities;
+          };
+          const actionsData = [getCategoryStub('test1'), getCategoryStub('test2')];
+          const collectionData = new CollectionDataStub()
+            .withActions(actionsData);
+          const categoryParserStub = new CategoryParserStub();
+          const context = new TestContext()
+            .withData(collectionData)
+            .withCollectionUtilitiesFactory(utilitiesFactory)
+            .withCategoryParser(categoryParserStub.get());
+          // act
+          context.parseCategoryCollection();
+          // assert
+          const usedUtilities = categoryParserStub.getUsedUtilities();
+          expect(usedUtilities).to.have.lengthOf(2);
+          expect(usedUtilities[0]).to.equal(expectedUtilities);
+          expect(usedUtilities[1]).to.equal(expectedUtilities);
+        });
+        describe('construction', () => {
+          it('creates utilities with correct functions data', () => {
+            // arrange
+            const expectedFunctionsData = [createFunctionDataWithCode()];
+            const collectionData = new CollectionDataStub()
+              .withFunctions(expectedFunctionsData);
+            let actualFunctionsData: ReadonlyArray<FunctionData> | undefined;
+            const utilitiesFactory: CategoryCollectionSpecificUtilitiesFactory = (data) => {
+              actualFunctionsData = data;
+              return new CategoryCollectionSpecificUtilitiesStub();
+            };
+            const context = new TestContext()
+              .withData(collectionData)
+              .withCollectionUtilitiesFactory(utilitiesFactory);
+            // act
+            context.parseCategoryCollection();
+            // assert
+            expect(actualFunctionsData).to.equal(expectedFunctionsData);
           });
-        }
+          it('creates utilities with correct scripting definition', () => {
+            // arrange
+            const expectedScripting = new ScriptingDefinitionStub();
+            const scriptingDefinitionParser: ScriptingDefinitionParser = () => {
+              return expectedScripting;
+            };
+            let actualScripting: IScriptingDefinition | undefined;
+            const utilitiesFactory: CategoryCollectionSpecificUtilitiesFactory = (_, scripting) => {
+              actualScripting = scripting;
+              return new CategoryCollectionSpecificUtilitiesStub();
+            };
+            const context = new TestContext()
+              .withCollectionUtilitiesFactory(utilitiesFactory)
+              .withScriptDefinitionParser(scriptingDefinitionParser);
+            // act
+            context.parseCategoryCollection();
+            // assert
+            expect(actualScripting).to.equal(expectedScripting);
+          });
+        });
       });
     });
     describe('scripting definition', () => {
-      it('parses scripting definition as expected', () => {
+      it('parses correctly', () => {
         // arrange
-        const collection = new CollectionDataStub();
-        const projectDetails = new ProjectDetailsStub();
-        const expected = new ScriptingDefinitionParser()
-          .parse(collection.scripting, projectDetails);
+        const {
+          categoryCollectionFactorySpy,
+          getInitParameters,
+        } = createCategoryCollectionFactorySpy();
+        const expected = new ScriptingDefinitionStub();
+        const scriptingDefinitionParser: ScriptingDefinitionParser = () => {
+          return expected;
+        };
+        const context = new TestContext()
+          .withCategoryCollectionFactory(categoryCollectionFactorySpy)
+          .withScriptDefinitionParser(scriptingDefinitionParser);
         // act
-        const actual = parseCategoryCollection(collection, projectDetails).scripting;
+        const actualCategoryCollection = context.parseCategoryCollection();
         // assert
-        expect(expected).to.deep.equal(actual);
+        const actualScripting = getInitParameters(actualCategoryCollection)?.scripting;
+        expect(expected).to.equal(actualScripting);
+      });
+      it('parses expected data', () => {
+        // arrange
+        const expectedData = new ScriptingDefinitionDataStub();
+        const collection = new CollectionDataStub()
+          .withScripting(expectedData);
+        let actualData: ScriptingDefinitionData | undefined;
+        const scriptingDefinitionParser
+        : ScriptingDefinitionParser = (data: ScriptingDefinitionData) => {
+          actualData = data;
+          return new ScriptingDefinitionStub();
+        };
+        const context = new TestContext()
+          .withScriptDefinitionParser(scriptingDefinitionParser)
+          .withData(collection);
+        // act
+        context.parseCategoryCollection();
+        // assert
+        expect(actualData).to.equal(expectedData);
+      });
+      it('parses with correct project details', () => {
+        // arrange
+        const expectedProjectDetails = new ProjectDetailsStub();
+        let actualDetails: ProjectDetails | undefined;
+        const scriptingDefinitionParser
+        : ScriptingDefinitionParser = (_, details: ProjectDetails) => {
+          actualDetails = details;
+          return new ScriptingDefinitionStub();
+        };
+        const context = new TestContext()
+          .withProjectDetails(expectedProjectDetails)
+          .withScriptDefinitionParser(scriptingDefinitionParser);
+        // act
+        context.parseCategoryCollection();
+        // assert
+        expect(actualDetails).to.equal(expectedProjectDetails);
       });
     });
     describe('os', () => {
-      it('parses as expected', () => {
+      it('parses correctly', () => {
         // arrange
+        const {
+          categoryCollectionFactorySpy,
+          getInitParameters,
+        } = createCategoryCollectionFactorySpy();
         const expectedOs = OperatingSystem.macOS;
         const osText = 'macos';
         const expectedName = 'os';
-        const collection = new CollectionDataStub()
+        const collectionData = new CollectionDataStub()
           .withOs(osText);
         const parserMock = new EnumParserStub<OperatingSystem>()
           .setup(expectedName, osText, expectedOs);
-        const projectDetails = new ProjectDetailsStub();
+        const context = new TestContext()
+          .withOsParser(parserMock)
+          .withCategoryCollectionFactory(categoryCollectionFactorySpy)
+          .withData(collectionData);
         // act
-        const actual = parseCategoryCollection(collection, projectDetails, parserMock);
+        const actualCollection = context.parseCategoryCollection();
         // assert
-        expect(actual.os).to.equal(expectedOs);
-      });
-    });
-    describe('functions', () => {
-      it('compiles script call with given function', () => {
-        // arrange
-        const expectedCode = 'code-from-the-function';
-        const functionName = 'function-name';
-        const scriptName = 'script-name';
-        const script = createScriptDataWithCall()
-          .withCall(new FunctionCallDataStub().withName(functionName).withParameters({}))
-          .withName(scriptName);
-        const func = createFunctionDataWithCode()
-          .withParametersObject([])
-          .withName(functionName)
-          .withCode(expectedCode);
-        const category = new CategoryDataStub()
-          .withChildren([script,
-            createScriptDataWithCode().withName('2')
-              .withRecommendationLevel(RecommendationLevel.Standard),
-            createScriptDataWithCode()
-              .withName('3').withRecommendationLevel(RecommendationLevel.Strict),
-          ]);
-        const collection = new CollectionDataStub()
-          .withActions([category])
-          .withFunctions([func]);
-        const projectDetails = new ProjectDetailsStub();
-        // act
-        const actual = parseCategoryCollection(collection, projectDetails);
-        // assert
-        const actualScript = actual.getScript(scriptName);
-        const actualCode = actualScript.code.execute;
-        expect(actualCode).to.equal(expectedCode);
+        const actualOs = getInitParameters(actualCollection)?.os;
+        expect(actualOs).to.equal(expectedOs);
       });
     });
   });
 });
+
+class TestContext {
+  private data: CollectionData = new CollectionDataStub();
+
+  private projectDetails: ProjectDetails = new ProjectDetailsStub();
+
+  private validator: TypeValidator = new TypeValidatorStub();
+
+  private osParser: EnumParser<OperatingSystem> = new EnumParserStub<OperatingSystem>()
+    .setupDefaultValue(OperatingSystem.Android);
+
+  private collectionUtilitiesFactory
+  : CategoryCollectionSpecificUtilitiesFactory = () => {
+      return new CategoryCollectionSpecificUtilitiesStub();
+    };
+
+  private scriptDefinitionParser: ScriptingDefinitionParser = () => new ScriptingDefinitionStub();
+
+  private categoryParser: CategoryParser = new CategoryParserStub().get();
+
+  private categoryCollectionFactory
+  : CategoryCollectionFactory = createCategoryCollectionFactorySpy().categoryCollectionFactorySpy;
+
+  public withData(data: CollectionData): this {
+    this.data = data;
+    return this;
+  }
+
+  public withCategoryParser(categoryParser: CategoryParser): this {
+    this.categoryParser = categoryParser;
+    return this;
+  }
+
+  public withCategoryCollectionFactory(categoryCollectionFactory: CategoryCollectionFactory): this {
+    this.categoryCollectionFactory = categoryCollectionFactory;
+    return this;
+  }
+
+  public withProjectDetails(projectDetails: ProjectDetails): this {
+    this.projectDetails = projectDetails;
+    return this;
+  }
+
+  public withOsParser(osParser: EnumParser<OperatingSystem>): this {
+    this.osParser = osParser;
+    return this;
+  }
+
+  public withScriptDefinitionParser(scriptDefinitionParser: ScriptingDefinitionParser): this {
+    this.scriptDefinitionParser = scriptDefinitionParser;
+    return this;
+  }
+
+  public withTypeValidator(typeValidator: TypeValidator): this {
+    this.validator = typeValidator;
+    return this;
+  }
+
+  public withCollectionUtilitiesFactory(
+    collectionUtilitiesFactory: CategoryCollectionSpecificUtilitiesFactory,
+  ): this {
+    this.collectionUtilitiesFactory = collectionUtilitiesFactory;
+    return this;
+  }
+
+  public parseCategoryCollection(): ReturnType<typeof parseCategoryCollection> {
+    return parseCategoryCollection(
+      this.data,
+      this.projectDetails,
+      {
+        osParser: this.osParser,
+        validator: this.validator,
+        parseScriptingDefinition: this.scriptDefinitionParser,
+        createUtilities: this.collectionUtilitiesFactory,
+        parseCategory: this.categoryParser,
+        createCategoryCollection: this.categoryCollectionFactory,
+      },
+    );
+  }
+}
diff --git a/tests/unit/application/Parser/ContextualError.spec.ts b/tests/unit/application/Parser/Common/ContextualError.spec.ts
similarity index 99%
rename from tests/unit/application/Parser/ContextualError.spec.ts
rename to tests/unit/application/Parser/Common/ContextualError.spec.ts
index b19da651..05ce0ab4 100644
--- a/tests/unit/application/Parser/ContextualError.spec.ts
+++ b/tests/unit/application/Parser/Common/ContextualError.spec.ts
@@ -1,6 +1,6 @@
 import { describe, it, expect } from 'vitest';
 import { CustomError } from '@/application/Common/CustomError';
-import { wrapErrorWithAdditionalContext } from '@/application/Parser/ContextualError';
+import { wrapErrorWithAdditionalContext } from '@/application/Parser/Common/ContextualError';
 
 describe('wrapErrorWithAdditionalContext', () => {
   it('preserves the original error when wrapped', () => {
diff --git a/tests/unit/application/Parser/ContextualErrorTester.ts b/tests/unit/application/Parser/Common/ContextualErrorTester.ts
similarity index 98%
rename from tests/unit/application/Parser/ContextualErrorTester.ts
rename to tests/unit/application/Parser/Common/ContextualErrorTester.ts
index 1c502c57..ef8ae353 100644
--- a/tests/unit/application/Parser/ContextualErrorTester.ts
+++ b/tests/unit/application/Parser/Common/ContextualErrorTester.ts
@@ -1,4 +1,4 @@
-import type { ErrorWithContextWrapper } from '@/application/Parser/ContextualError';
+import type { ErrorWithContextWrapper } from '@/application/Parser/Common/ContextualError';
 import { expectExists } from '@tests/shared/Assertions/ExpectExists';
 import { formatAssertionMessage } from '@tests/shared/FormatAssertionMessage';
 import { indentText } from '@tests/shared/Text';
diff --git a/tests/unit/application/Parser/Common/TypeValidator.spec.ts b/tests/unit/application/Parser/Common/TypeValidator.spec.ts
new file mode 100644
index 00000000..4b8a273a
--- /dev/null
+++ b/tests/unit/application/Parser/Common/TypeValidator.spec.ts
@@ -0,0 +1,157 @@
+import { describe, it, expect } from 'vitest';
+import { createTypeValidator } from '@/application/Parser/Common/TypeValidator';
+import { itEachAbsentObjectValue } from '@tests/unit/shared/TestCases/AbsentTests';
+
+describe('createTypeValidator', () => {
+  describe('assertObject', () => {
+    describe('with valid object', () => {
+      it('accepts object with allowed properties', () => {
+        // arrange
+        const expectedProperties = ['expected1', 'expected2'];
+        const validValue = createObjectWithProperties(expectedProperties);
+        const { assertObject } = createTypeValidator();
+        // act
+        const act = () => assertObject({
+          value: validValue,
+          valueName: 'unimportant name',
+          allowedProperties: expectedProperties,
+        });
+        // assert
+        expect(act).to.not.throw();
+      });
+      it('accepts object with extra unspecified properties', () => {
+        // arrange
+        const validValue = createObjectWithProperties(['unevaluated property']);
+        const { assertObject } = createTypeValidator();
+        // act
+        const act = () => assertObject({
+          value: validValue,
+          valueName: 'unimportant name',
+        });
+        // assert
+        expect(act).to.not.throw();
+      });
+    });
+    describe('with invalid object', () => {
+      describe('throws error for missing object', () => {
+        itEachAbsentObjectValue((absentValue) => {
+          // arrange
+          const valueName = 'absent object value';
+          const expectedMessage = `'${valueName}' is missing.`;
+          const { assertObject } = createTypeValidator();
+          // act
+          const act = () => assertObject({ value: absentValue, valueName });
+          // assert
+          expect(act).to.throw(expectedMessage);
+        });
+      });
+      it('throws error for object without properties', () => {
+        // arrange
+        const emptyObjectValue: object = {};
+        const valueName = 'empty object without properties.';
+        const expectedMessage = `'${valueName}' is an empty object without properties.`;
+        const { assertObject } = createTypeValidator();
+        // act
+        const act = () => assertObject({ value: emptyObjectValue, valueName });
+        // assert
+        expect(act).to.throw(expectedMessage);
+      });
+      describe('incorrect data type', () => {
+        // arrange
+        const testScenarios: readonly {
+          readonly value: unknown;
+          readonly valueName: string;
+        }[] = [
+          {
+            value: ['1', '2'],
+            valueName: 'array of strings',
+          },
+          {
+            value: true,
+            valueName: 'true boolean',
+          },
+          {
+            value: 35,
+            valueName: 'number',
+          },
+        ];
+        testScenarios.forEach(({ value, valueName }) => {
+          it(`throws error for ${valueName} passed as object`, () => {
+            // arrange
+            const expectedMessage = `'${valueName}' is not an object.`;
+            const { assertObject } = createTypeValidator();
+            // act
+            const act = () => assertObject({ value, valueName });
+            // assert
+            expect(act).to.throw(expectedMessage);
+          });
+        });
+      });
+      it('throws error for object with disallowed properties', () => {
+        // arrange
+        const valueName = 'value with unexpected properties';
+        const unexpectedProperties = ['unexpected-property-1', 'unexpected-property-2'];
+        const expectedError = `'${valueName}' has disallowed properties: ${unexpectedProperties.join(', ')}.`;
+        const expectedProperties = ['expected1', 'expected2'];
+        const value = createObjectWithProperties(
+          [...expectedProperties, ...unexpectedProperties],
+        );
+        const { assertObject } = createTypeValidator();
+        // act
+        const act = () => assertObject({
+          value,
+          valueName,
+          allowedProperties: expectedProperties,
+        });
+        // assert
+        expect(act).to.throw(expectedError);
+      });
+    });
+  });
+  describe('assertNonEmptyCollection', () => {
+    describe('with valid collection', () => {
+      it('accepts non-empty collection', () => {
+        // arrange
+        const validValue = ['array', 'of', 'strings'];
+        const { assertNonEmptyCollection } = createTypeValidator();
+        // act
+        const act = () => assertNonEmptyCollection({ value: validValue, valueName: 'unimportant name' });
+        // assert
+        expect(act).to.not.throw();
+      });
+    });
+    describe('with invalid collection', () => {
+      describe('throws error for missing collection', () => {
+        itEachAbsentObjectValue((absentValue) => {
+          // arrange
+          const valueName = 'absent collection value';
+          const expectedMessage = `'${valueName}' is missing.`;
+          const { assertNonEmptyCollection } = createTypeValidator();
+          // act
+          const act = () => assertNonEmptyCollection({ value: absentValue, valueName });
+          // assert
+          expect(act).to.throw(expectedMessage);
+        });
+      });
+      it('throws error for empty collection', () => {
+        // arrange
+        const emptyArrayValue = [];
+        const valueName = 'empty collection value';
+        const expectedMessage = `'${valueName}' cannot be an empty array.`;
+        const { assertNonEmptyCollection } = createTypeValidator();
+        // act
+        const act = () => assertNonEmptyCollection({ value: emptyArrayValue, valueName });
+        // assert
+        expect(act).to.throw(expectedMessage);
+      });
+    });
+  });
+});
+
+function createObjectWithProperties(properties: readonly string[]): object {
+  const object = {};
+  properties.forEach((propertyName) => {
+    object[propertyName] = 'arbitrary value';
+  });
+  return object;
+}
diff --git a/tests/unit/application/Parser/Executable/CategoryParser.spec.ts b/tests/unit/application/Parser/Executable/CategoryParser.spec.ts
index 7b668e78..a101c753 100644
--- a/tests/unit/application/Parser/Executable/CategoryParser.spec.ts
+++ b/tests/unit/application/Parser/Executable/CategoryParser.spec.ts
@@ -5,10 +5,9 @@ import { type ScriptParser } from '@/application/Parser/Executable/Script/Script
 import { type DocsParser } from '@/application/Parser/Executable/DocumentationParser';
 import { CategoryCollectionSpecificUtilitiesStub } from '@tests/unit/shared/Stubs/CategoryCollectionSpecificUtilitiesStub';
 import { CategoryDataStub } from '@tests/unit/shared/Stubs/CategoryDataStub';
-import { getAbsentCollectionTestCases } from '@tests/unit/shared/TestCases/AbsentTests';
 import { ExecutableType } from '@/application/Parser/Executable/Validation/ExecutableType';
 import { createScriptDataWithCall, createScriptDataWithCode } from '@tests/unit/shared/Stubs/ScriptDataStub';
-import type { ErrorWithContextWrapper } from '@/application/Parser/ContextualError';
+import type { ErrorWithContextWrapper } from '@/application/Parser/Common/ContextualError';
 import { ErrorWrapperStub } from '@tests/unit/shared/Stubs/ErrorWrapperStub';
 import type { ExecutableValidatorFactory } from '@/application/Parser/Executable/Validation/ExecutableValidator';
 import { ExecutableValidatorStub, createExecutableValidatorFactoryStub } from '@tests/unit/shared/Stubs/ExecutableValidatorStub';
@@ -20,8 +19,9 @@ import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
 import { ScriptParserStub } from '@tests/unit/shared/Stubs/ScriptParserStub';
 import { formatAssertionMessage } from '@tests/shared/FormatAssertionMessage';
 import { indentText } from '@tests/shared/Text';
-import { itThrowsContextualError } from '../ContextualErrorTester';
-import { itValidatesName, itValidatesDefinedData, itAsserts } from './Validation/ExecutableValidationTester';
+import type { NonEmptyCollectionAssertion, ObjectAssertion } from '@/application/Parser/Common/TypeValidator';
+import { itThrowsContextualError } from '../Common/ContextualErrorTester';
+import { itValidatesName, itValidatesType, itAsserts } from './Validation/ExecutableValidationTester';
 import { generateDataValidationTestScenarios } from './Validation/DataValidationTestScenarioGenerator';
 
 describe('CategoryParser', () => {
@@ -49,14 +49,18 @@ describe('CategoryParser', () => {
           };
         });
       });
-      describe('validates for defined data', () => {
+      describe('validates for unknown object', () => {
         // arrange
         const category = new CategoryDataStub();
         const expectedContext: CategoryErrorContext = {
           type: ExecutableType.Category,
           self: category,
         };
-        itValidatesDefinedData(
+        const expectedAssertion: ObjectAssertion<unknown> = {
+          value: category,
+          valueName: 'Executable',
+        };
+        itValidatesType(
           (validatorFactory) => {
             // act
             new TestBuilder()
@@ -65,58 +69,65 @@ describe('CategoryParser', () => {
               .parseCategory();
             // assert
             return {
-              expectedDataToValidate: category,
+              assertValidation: (validator) => validator.assertObject(expectedAssertion),
               expectedErrorContext: expectedContext,
             };
           },
         );
       });
-      describe('validates that category has some children', () => {
-        const categoryName = 'test';
-        const testScenarios = generateDataValidationTestScenarios<CategoryData>({
-          expectFail: getAbsentCollectionTestCases<ExecutableData>().map(({
-            valueName, absentValue: absentCollectionValue,
-          }) => ({
-            description: `with \`${valueName}\` value as children`,
-            data: new CategoryDataStub()
-              .withName(categoryName)
-              .withChildren(absentCollectionValue as unknown as ExecutableData[]),
-          })),
-          expectPass: [{
-            description: 'has single children',
-            data: new CategoryDataStub()
-              .withName(categoryName)
-              .withChildren([createScriptDataWithCode()]),
-          }],
-        });
-        testScenarios.forEach(({
-          description, expectedPass, data: categoryData,
-        }) => {
-          describe(description, () => {
-            itAsserts({
-              expectedConditionResult: expectedPass,
-              test: (validatorFactory) => {
-                const expectedMessage = `"${categoryName}" has no children.`;
-                const expectedContext: CategoryErrorContext = {
-                  type: ExecutableType.Category,
-                  self: categoryData,
-                };
-                // act
-                try {
-                  new TestBuilder()
-                    .withData(categoryData)
-                    .withValidatorFactory(validatorFactory)
-                    .parseCategory();
-                } catch { /* It may throw due to assertions not being evaluated */ }
-                // assert
-                return {
-                  expectedErrorMessage: expectedMessage,
-                  expectedErrorContext: expectedContext,
-                };
-              },
-            });
-          });
-        });
+      describe('validates for category', () => {
+        // arrange
+        const category = new CategoryDataStub();
+        const expectedContext: CategoryErrorContext = {
+          type: ExecutableType.Category,
+          self: category,
+        };
+        const expectedAssertion: ObjectAssertion<CategoryData> = {
+          value: category,
+          valueName: category.category,
+          allowedProperties: ['docs', 'children', 'category'],
+        };
+        itValidatesType(
+          (validatorFactory) => {
+            // act
+            new TestBuilder()
+              .withData(category)
+              .withValidatorFactory(validatorFactory)
+              .parseCategory();
+            // assert
+            return {
+              assertValidation: (validator) => validator.assertObject(expectedAssertion),
+              expectedErrorContext: expectedContext,
+            };
+          },
+        );
+      });
+      describe('validates children for non-empty collection', () => {
+        // arrange
+        const category = new CategoryDataStub()
+          .withChildren([createScriptDataWithCode()]);
+        const expectedContext: CategoryErrorContext = {
+          type: ExecutableType.Category,
+          self: category,
+        };
+        const expectedAssertion: NonEmptyCollectionAssertion = {
+          value: category.children,
+          valueName: category.category,
+        };
+        itValidatesType(
+          (validatorFactory) => {
+            // act
+            new TestBuilder()
+              .withData(category)
+              .withValidatorFactory(validatorFactory)
+              .parseCategory();
+            // assert
+            return {
+              assertValidation: (validator) => validator.assertObject(expectedAssertion),
+              expectedErrorContext: expectedContext,
+            };
+          },
+        );
       });
       describe('validates that a child is a category or a script', () => {
         // arrange
@@ -171,7 +182,7 @@ describe('CategoryParser', () => {
         });
       });
       describe('validates children recursively', () => {
-        describe('validates (1th-level) child data', () => {
+        describe('validates (1th-level) child type', () => {
           // arrange
           const expectedName = 'child category';
           const child = new CategoryDataStub()
@@ -183,7 +194,11 @@ describe('CategoryParser', () => {
             self: child,
             parentCategory: parent,
           };
-          itValidatesDefinedData(
+          const expectedAssertion: ObjectAssertion<unknown> = {
+            value: child,
+            valueName: 'Executable',
+          };
+          itValidatesType(
             (validatorFactory) => {
               // act
               new TestBuilder()
@@ -192,7 +207,7 @@ describe('CategoryParser', () => {
                 .parseCategory();
               // assert
               return {
-                expectedDataToValidate: child,
+                assertValidation: (validator) => validator.assertObject(expectedAssertion),
                 expectedErrorContext: expectedContext,
               };
             },
diff --git a/tests/unit/application/Parser/Executable/DocumentationParser.spec.ts b/tests/unit/application/Parser/Executable/DocumentationParser.spec.ts
index 507961b9..678d74b6 100644
--- a/tests/unit/application/Parser/Executable/DocumentationParser.spec.ts
+++ b/tests/unit/application/Parser/Executable/DocumentationParser.spec.ts
@@ -18,7 +18,7 @@ describe('DocumentationParser', () => {
     });
     describe('throws when type is unexpected', () => {
       // arrange
-      const expectedTypeError = 'docs field (documentation) must be an array of strings';
+      const expectedTypeError = 'docs field (documentation) must be a single string or an array of strings.';
       const wrongTypedValue = 22 as never;
       const testCases: ReadonlyArray<{
         readonly name: string;
diff --git a/tests/unit/application/Parser/Executable/Script/Compiler/Expressions/Parser/Regex/RegexParser.spec.ts b/tests/unit/application/Parser/Executable/Script/Compiler/Expressions/Parser/Regex/RegexParser.spec.ts
index 0283dae5..425bb304 100644
--- a/tests/unit/application/Parser/Executable/Script/Compiler/Expressions/Parser/Regex/RegexParser.spec.ts
+++ b/tests/unit/application/Parser/Executable/Script/Compiler/Expressions/Parser/Regex/RegexParser.spec.ts
@@ -8,7 +8,7 @@ import {
 import { ExpressionPosition } from '@/application/Parser/Executable/Script/Compiler/Expressions/Expression/ExpressionPosition';
 import { itEachAbsentStringValue } from '@tests/unit/shared/TestCases/AbsentTests';
 import { collectExceptionMessage } from '@tests/unit/shared/ExceptionCollector';
-import { itThrowsContextualError } from '@tests/unit/application/Parser/ContextualErrorTester';
+import { itThrowsContextualError } from '@tests/unit/application/Parser/Common/ContextualErrorTester';
 import { ExpressionStub } from '@tests/unit/shared/Stubs/ExpressionStub';
 import { FunctionParameterCollectionStub } from '@tests/unit/shared/Stubs/FunctionParameterCollectionStub';
 import type { IExpression } from '@/application/Parser/Executable/Script/Compiler/Expressions/Expression/IExpression';
diff --git a/tests/unit/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/SingleCall/NestedFunctionCallCompiler.spec.ts b/tests/unit/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/SingleCall/NestedFunctionCallCompiler.spec.ts
index 3063875f..ba5df9e3 100644
--- a/tests/unit/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/SingleCall/NestedFunctionCallCompiler.spec.ts
+++ b/tests/unit/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/SingleCall/NestedFunctionCallCompiler.spec.ts
@@ -9,8 +9,8 @@ import { SingleCallCompilerStub } from '@tests/unit/shared/Stubs/SingleCallCompi
 import { CompiledCodeStub } from '@tests/unit/shared/Stubs/CompiledCodeStub';
 import type { FunctionCall } from '@/application/Parser/Executable/Script/Compiler/Function/Call/FunctionCall';
 import type { CompiledCode } from '@/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/CompiledCode';
-import { itThrowsContextualError } from '@tests/unit/application/Parser/ContextualErrorTester';
-import type { ErrorWithContextWrapper } from '@/application/Parser/ContextualError';
+import { itThrowsContextualError } from '@tests/unit/application/Parser/Common/ContextualErrorTester';
+import type { ErrorWithContextWrapper } from '@/application/Parser/Common/ContextualError';
 import { errorWithContextWrapperStub } from '@tests/unit/shared/Stubs/ErrorWithContextWrapperStub';
 
 describe('NestedFunctionCallCompiler', () => {
diff --git a/tests/unit/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/SingleCall/Strategies/Argument/NestedFunctionArgumentCompiler.spec.ts b/tests/unit/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/SingleCall/Strategies/Argument/NestedFunctionArgumentCompiler.spec.ts
index 1d85c410..edac5c28 100644
--- a/tests/unit/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/SingleCall/Strategies/Argument/NestedFunctionArgumentCompiler.spec.ts
+++ b/tests/unit/application/Parser/Executable/Script/Compiler/Function/Call/Compiler/SingleCall/Strategies/Argument/NestedFunctionArgumentCompiler.spec.ts
@@ -11,8 +11,8 @@ import { FunctionCallArgumentCollectionStub } from '@tests/unit/shared/Stubs/Fun
 import { createSharedFunctionStubWithCode } from '@tests/unit/shared/Stubs/SharedFunctionStub';
 import { FunctionParameterCollectionStub } from '@tests/unit/shared/Stubs/FunctionParameterCollectionStub';
 import { SharedFunctionCollectionStub } from '@tests/unit/shared/Stubs/SharedFunctionCollectionStub';
-import { itThrowsContextualError } from '@tests/unit/application/Parser/ContextualErrorTester';
-import type { ErrorWithContextWrapper } from '@/application/Parser/ContextualError';
+import { itThrowsContextualError } from '@tests/unit/application/Parser/Common/ContextualErrorTester';
+import type { ErrorWithContextWrapper } from '@/application/Parser/Common/ContextualError';
 import { errorWithContextWrapperStub } from '@tests/unit/shared/Stubs/ErrorWithContextWrapperStub';
 
 describe('NestedFunctionArgumentCompiler', () => {
diff --git a/tests/unit/application/Parser/Executable/Script/Compiler/Function/SharedFunctionsParser.spec.ts b/tests/unit/application/Parser/Executable/Script/Compiler/Function/SharedFunctionsParser.spec.ts
index b172b2fc..96852733 100644
--- a/tests/unit/application/Parser/Executable/Script/Compiler/Function/SharedFunctionsParser.spec.ts
+++ b/tests/unit/application/Parser/Executable/Script/Compiler/Function/SharedFunctionsParser.spec.ts
@@ -13,10 +13,10 @@ import { CodeValidatorStub } from '@tests/unit/shared/Stubs/CodeValidatorStub';
 import type { ICodeValidator } from '@/application/Parser/Executable/Script/Validation/ICodeValidator';
 import { NoEmptyLines } from '@/application/Parser/Executable/Script/Validation/Rules/NoEmptyLines';
 import { NoDuplicatedLines } from '@/application/Parser/Executable/Script/Validation/Rules/NoDuplicatedLines';
-import type { ErrorWithContextWrapper } from '@/application/Parser/ContextualError';
+import type { ErrorWithContextWrapper } from '@/application/Parser/Common/ContextualError';
 import { FunctionParameterStub } from '@tests/unit/shared/Stubs/FunctionParameterStub';
 import { errorWithContextWrapperStub } from '@tests/unit/shared/Stubs/ErrorWithContextWrapperStub';
-import { itThrowsContextualError } from '@tests/unit/application/Parser/ContextualErrorTester';
+import { itThrowsContextualError } from '@tests/unit/application/Parser/Common/ContextualErrorTester';
 import type { FunctionParameterCollectionFactory } from '@/application/Parser/Executable/Script/Compiler/Function/Parameter/FunctionParameterCollectionFactory';
 import { FunctionParameterCollectionStub } from '@tests/unit/shared/Stubs/FunctionParameterCollectionStub';
 import { expectCallsFunctionBody, expectCodeFunctionBody } from './ExpectFunctionBodyType';
diff --git a/tests/unit/application/Parser/Executable/Script/Compiler/ScriptCompiler.spec.ts b/tests/unit/application/Parser/Executable/Script/Compiler/ScriptCompiler.spec.ts
index a0e64a89..d014d4a1 100644
--- a/tests/unit/application/Parser/Executable/Script/Compiler/ScriptCompiler.spec.ts
+++ b/tests/unit/application/Parser/Executable/Script/Compiler/ScriptCompiler.spec.ts
@@ -16,12 +16,12 @@ import { CodeValidatorStub } from '@tests/unit/shared/Stubs/CodeValidatorStub';
 import { NoEmptyLines } from '@/application/Parser/Executable/Script/Validation/Rules/NoEmptyLines';
 import { CompiledCodeStub } from '@tests/unit/shared/Stubs/CompiledCodeStub';
 import { createScriptDataWithCall, createScriptDataWithCode } from '@tests/unit/shared/Stubs/ScriptDataStub';
-import type { ErrorWithContextWrapper } from '@/application/Parser/ContextualError';
+import type { ErrorWithContextWrapper } from '@/application/Parser/Common/ContextualError';
 import { errorWithContextWrapperStub } from '@tests/unit/shared/Stubs/ErrorWithContextWrapperStub';
 import { ScriptCodeStub } from '@tests/unit/shared/Stubs/ScriptCodeStub';
 import type { ScriptCodeFactory } from '@/domain/Executables/Script/Code/ScriptCodeFactory';
 import { createScriptCodeFactoryStub } from '@tests/unit/shared/Stubs/ScriptCodeFactoryStub';
-import { itThrowsContextualError } from '@tests/unit/application/Parser/ContextualErrorTester';
+import { itThrowsContextualError } from '@tests/unit/application/Parser/Common/ContextualErrorTester';
 
 describe('ScriptCompiler', () => {
   describe('canCompile', () => {
diff --git a/tests/unit/application/Parser/Executable/Script/ScriptParser.spec.ts b/tests/unit/application/Parser/Executable/Script/ScriptParser.spec.ts
index 49bf9fd3..de27f5b2 100644
--- a/tests/unit/application/Parser/Executable/Script/ScriptParser.spec.ts
+++ b/tests/unit/application/Parser/Executable/Script/ScriptParser.spec.ts
@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest';
-import type { ScriptData } from '@/application/collections/';
+import type { ScriptData, CallScriptData, CodeScriptData } from '@/application/collections/';
 import { parseScript, type ScriptFactory } from '@/application/Parser/Executable/Script/ScriptParser';
 import { type DocsParser } from '@/application/Parser/Executable/DocumentationParser';
 import { RecommendationLevel } from '@/domain/Executables/Script/RecommendationLevel';
@@ -8,14 +8,13 @@ import { ScriptCompilerStub } from '@tests/unit/shared/Stubs/ScriptCompilerStub'
 import { createScriptDataWithCall, createScriptDataWithCode, createScriptDataWithoutCallOrCodes } from '@tests/unit/shared/Stubs/ScriptDataStub';
 import { EnumParserStub } from '@tests/unit/shared/Stubs/EnumParserStub';
 import { ScriptCodeStub } from '@tests/unit/shared/Stubs/ScriptCodeStub';
-import { CategoryCollectionSpecificUtilitiesStub } from '@tests/unit/shared/Stubs/CategoryCollectionSpecificUtilitiesStub';
 import { LanguageSyntaxStub } from '@tests/unit/shared/Stubs/LanguageSyntaxStub';
-import type { IEnumParser } from '@/application/Common/Enum';
+import type { EnumParser } from '@/application/Common/Enum';
 import { NoEmptyLines } from '@/application/Parser/Executable/Script/Validation/Rules/NoEmptyLines';
 import { NoDuplicatedLines } from '@/application/Parser/Executable/Script/Validation/Rules/NoDuplicatedLines';
 import { CodeValidatorStub } from '@tests/unit/shared/Stubs/CodeValidatorStub';
 import type { ICodeValidator } from '@/application/Parser/Executable/Script/Validation/ICodeValidator';
-import type { ErrorWithContextWrapper } from '@/application/Parser/ContextualError';
+import type { ErrorWithContextWrapper } from '@/application/Parser/Common/ContextualError';
 import { ErrorWrapperStub } from '@tests/unit/shared/Stubs/ErrorWrapperStub';
 import type { ExecutableValidatorFactory } from '@/application/Parser/Executable/Validation/ExecutableValidator';
 import { ExecutableValidatorStub, createExecutableValidatorFactoryStub } from '@tests/unit/shared/Stubs/ExecutableValidatorStub';
@@ -26,9 +25,11 @@ import { createScriptCodeFactoryStub } from '@tests/unit/shared/Stubs/ScriptCode
 import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
 import { createScriptFactorySpy } from '@tests/unit/shared/Stubs/ScriptFactoryStub';
 import { expectExists } from '@tests/shared/Assertions/ExpectExists';
-import { itThrowsContextualError } from '@tests/unit/application/Parser/ContextualErrorTester';
+import { itThrowsContextualError } from '@tests/unit/application/Parser/Common/ContextualErrorTester';
+import { CategoryCollectionSpecificUtilitiesStub } from '@tests/unit/shared/Stubs/CategoryCollectionSpecificUtilitiesStub';
 import type { CategoryCollectionSpecificUtilities } from '@/application/Parser/Executable/CategoryCollectionSpecificUtilities';
-import { itAsserts, itValidatesDefinedData, itValidatesName } from '../Validation/ExecutableValidationTester';
+import type { ObjectAssertion } from '@/application/Parser/Common/TypeValidator';
+import { itAsserts, itValidatesType, itValidatesName } from '../Validation/ExecutableValidationTester';
 import { generateDataValidationTestScenarios } from '../Validation/DataValidationTestScenarioGenerator';
 
 describe('ScriptParser', () => {
@@ -290,7 +291,14 @@ describe('ScriptParser', () => {
           type: ExecutableType.Script,
           self: expectedScript,
         };
-        itValidatesDefinedData(
+        const expectedAssertion: ObjectAssertion<CallScriptData & CodeScriptData> = {
+          value: expectedScript,
+          valueName: expectedScript.name,
+          allowedProperties: [
+            'name', 'recommend', 'code', 'revertCode', 'call', 'docs',
+          ],
+        };
+        itValidatesType(
           (validatorFactory) => {
             // act
             new TestContext()
@@ -301,6 +309,7 @@ describe('ScriptParser', () => {
             return {
               expectedDataToValidate: expectedScript,
               expectedErrorContext: expectedContext,
+              assertValidation: (validator) => validator.assertObject(expectedAssertion),
             };
           },
         );
@@ -430,7 +439,7 @@ class TestContext {
   private collectionUtilities
   : CategoryCollectionSpecificUtilities = new CategoryCollectionSpecificUtilitiesStub();
 
-  private levelParser: IEnumParser<RecommendationLevel> = new EnumParserStub<RecommendationLevel>()
+  private levelParser: EnumParser<RecommendationLevel> = new EnumParserStub<RecommendationLevel>()
     .setupDefaultValue(RecommendationLevel.Standard);
 
   private scriptFactory: ScriptFactory = createScriptFactorySpy().scriptFactorySpy;
@@ -464,7 +473,7 @@ class TestContext {
     return this;
   }
 
-  public withParser(parser: IEnumParser<RecommendationLevel>): this {
+  public withParser(parser: EnumParser<RecommendationLevel>): this {
     this.levelParser = parser;
     return this;
   }
diff --git a/tests/unit/application/Parser/Executable/Validation/ExecutableValidationTester.ts b/tests/unit/application/Parser/Executable/Validation/ExecutableValidationTester.ts
index df98f1cc..35ecabd5 100644
--- a/tests/unit/application/Parser/Executable/Validation/ExecutableValidationTester.ts
+++ b/tests/unit/application/Parser/Executable/Validation/ExecutableValidationTester.ts
@@ -3,10 +3,11 @@ import type { ExecutableValidator, ExecutableValidatorFactory } from '@/applicat
 import type { ExecutableErrorContext } from '@/application/Parser/Executable/Validation/ExecutableErrorContext';
 import { ExecutableValidatorStub } from '@tests/unit/shared/Stubs/ExecutableValidatorStub';
 import { expectExists } from '@tests/shared/Assertions/ExpectExists';
-import type { ExecutableData } from '@/application/collections/';
 import type { FunctionKeys } from '@/TypeHelpers';
 import { formatAssertionMessage } from '@tests/shared/FormatAssertionMessage';
 import { indentText } from '@tests/shared/Text';
+import { TypeValidatorStub } from '@tests/unit/shared/Stubs/TypeValidatorStub';
+import { expectDeepIncludes } from '@tests/shared/Assertions/ExpectDeepIncludes';
 
 type ValidationTestFunction<TExpectation> = (
   factory: ExecutableValidatorFactory,
@@ -52,39 +53,41 @@ export function itValidatesName(
   });
 }
 
-interface ValidDataExpectation {
-  readonly expectedDataToValidate: ExecutableData;
+interface TypeAssertionExpectation {
   readonly expectedErrorContext: ExecutableErrorContext;
+  readonly assertValidation: (validator: TypeValidatorStub) => void;
 }
 
-export function itValidatesDefinedData(
-  test: ValidationTestFunction<ValidDataExpectation>,
+export function itValidatesType(
+  test: ValidationTestFunction<TypeAssertionExpectation>,
 ) {
-  it('validates data', () => {
+  it('validates type', () => {
     // arrange
     const validator = new ExecutableValidatorStub();
     const factoryStub: ExecutableValidatorFactory = () => validator;
     // act
     test(factoryStub);
     // assert
-    const call = validator.callHistory.find((c) => c.methodName === 'assertDefined');
+    const call = validator.callHistory.find((c) => c.methodName === 'assertType');
     expectExists(call);
   });
-  it('validates data with correct data', () => {
+  it('validates type using specified validator', () => {
     // arrange
+    const typeValidator = new TypeValidatorStub();
     const validator = new ExecutableValidatorStub();
     const factoryStub: ExecutableValidatorFactory = () => validator;
     // act
     const expectation = test(factoryStub);
     // assert
-    const expectedData = expectation.expectedDataToValidate;
-    const calls = validator.callHistory.filter((c) => c.methodName === 'assertDefined');
-    const names = calls.flatMap((c) => c.args[0]);
-    expect(names).to.include(expectedData);
+    const calls = validator.callHistory.filter((c) => c.methodName === 'assertType');
+    const args = calls.map((c) => c.args as Parameters<ExecutableValidator['assertType']>);
+    const validateFunctions = args.flatMap((c) => c[0]);
+    validateFunctions.forEach((validate) => validate(typeValidator));
+    expectation.assertValidation(typeValidator);
   });
-  it('validates data with correct context', () => {
+  it('validates type with correct context', () => {
     expectCorrectContextForFunctionCall({
-      methodName: 'assertDefined',
+      methodName: 'assertType',
       act: test,
       expectContext: (expectation) => expectation.expectedErrorContext,
     });
@@ -185,34 +188,5 @@ function expectCorrectContextForFunctionCall<T>(testScenario: {
   const providedContexts = createdValidators
     .filter((v) => v.validator.callHistory.find((c) => c.methodName === methodName))
     .map((v) => v.context);
-  expectDeepIncludes( // to.deep.include is not working
-    providedContexts,
-    expectedContext,
-    formatAssertionMessage([
-      'Error context mismatch.',
-      'Provided contexts do not include the expected context.',
-      'Expected context:',
-      indentText(JSON.stringify(expectedContext, undefined, 2)),
-      'Provided contexts:',
-      indentText(JSON.stringify(providedContexts, undefined, 2)),
-    ]),
-  );
-}
-
-function expectDeepIncludes<T>(
-  array: readonly T[],
-  item: T,
-  message: string,
-) {
-  const serializeItem = (c) => JSON.stringify(c);
-  const serializedContexts = array.map((c) => serializeItem(c));
-  const serializedExpectedContext = serializeItem(item);
-  expect(serializedContexts).to.include(serializedExpectedContext, formatAssertionMessage([
-    'Error context mismatch.',
-    'Provided contexts do not include the expected context.',
-    'Expected context:',
-    indentText(JSON.stringify(message, undefined, 2)),
-    'Provided contexts:',
-    indentText(JSON.stringify(message, undefined, 2)),
-  ]));
+  expectDeepIncludes(providedContexts, expectedContext);
 }
diff --git a/tests/unit/application/Parser/Executable/Validation/ExecutableValidator.spec.ts b/tests/unit/application/Parser/Executable/Validation/ExecutableValidator.spec.ts
index 68660889..485a826a 100644
--- a/tests/unit/application/Parser/Executable/Validation/ExecutableValidator.spec.ts
+++ b/tests/unit/application/Parser/Executable/Validation/ExecutableValidator.spec.ts
@@ -1,12 +1,12 @@
 import { describe, it, expect } from 'vitest';
-import { CategoryDataStub } from '@tests/unit/shared/Stubs/CategoryDataStub';
-import type { ExecutableData } from '@/application/collections/';
 import { createExecutableErrorContextStub } from '@tests/unit/shared/Stubs/ExecutableErrorContextStub';
 import type { ExecutableErrorContext } from '@/application/Parser/Executable/Validation/ExecutableErrorContext';
 import { collectExceptionMessage } from '@tests/unit/shared/ExceptionCollector';
 import { ContextualExecutableValidator, createExecutableDataValidator, type ExecutableValidator } from '@/application/Parser/Executable/Validation/ExecutableValidator';
 import type { ExecutableContextErrorMessageCreator } from '@/application/Parser/Executable/Validation/ExecutableErrorContextMessage';
-import { getAbsentObjectTestCases, getAbsentStringTestCases } from '@tests/unit/shared/TestCases/AbsentTests';
+import { getAbsentStringTestCases } from '@tests/unit/shared/TestCases/AbsentTests';
+import { TypeValidatorStub } from '@tests/unit/shared/Stubs/TypeValidatorStub';
+import type { TypeValidator } from '@/application/Parser/Common/TypeValidator';
 
 describe('createExecutableDataValidator', () => {
   it(`returns an instance of ${ContextualExecutableValidator.name}`, () => {
@@ -63,43 +63,41 @@ describe('ContextualExecutableValidator', () => {
       expect(act).to.not.throw();
     });
   });
-  describe('assertDefined', () => {
-    describe('throws when data is missing', () => {
+  describe('assertType', () => {
+    describe('rethrows when action throws', () => {
       // arrange
-      const testScenarios: readonly {
-        readonly description: string;
-        readonly invalidData: unknown;
-      }[] = [
-        ...getAbsentObjectTestCases().map((testCase) => ({
-          description: `absent object (${testCase.valueName})`,
-          invalidData: testCase.absentValue,
-        })),
-        {
-          description: 'empty object',
-          invalidData: {},
-        },
-      ];
-      testScenarios.forEach(({ description, invalidData }) => {
-        describe(`given "${description}"`, () => {
-          const expectedMessage = 'missing executable data';
-          itThrowsCorrectly({
-            // act
-            throwingAction: (sut: ExecutableValidator) => {
-              sut.assertDefined(invalidData as ExecutableData);
-            },
-            // assert
-            expectedMessage,
+      const expectedMessage = 'Error thrown by action';
+      itThrowsCorrectly({
+        // act
+        throwingAction: (sut: ExecutableValidator) => {
+          sut.assertType(() => {
+            throw new Error(expectedMessage);
           });
-        });
+        },
+        // assert
+        expectedMessage,
       });
     });
-    it('does not throw if data is defined', () => {
+    it('provides correct validator', () => {
+      // arrange
+      const expectedValidator = new TypeValidatorStub();
+      const sut = new ValidatorBuilder()
+        .withTypeValidator(expectedValidator)
+        .build();
+      let actualValidator: TypeValidator | undefined;
+      // act
+      sut.assertType((validator) => {
+        actualValidator = validator;
+      });
+      // assert
+      expect(expectedValidator).to.equal(actualValidator);
+    });
+    it('does not throw if action does not throw', () => {
       // arrange
-      const data = new CategoryDataStub();
       const sut = new ValidatorBuilder()
         .build();
       // act
-      const act = () => sut.assertDefined(data);
+      const act = () => sut.assertType(() => { /* Does not throw */ });
       // assert
       expect(act).to.not.throw();
     });
@@ -223,6 +221,8 @@ class ValidatorBuilder {
 
   private errorMessageCreator: ExecutableContextErrorMessageCreator = () => `[${ValidatorBuilder.name}] stub error message`;
 
+  private typeValidator: TypeValidator = new TypeValidatorStub();
+
   public withErrorMessageCreator(errorMessageCreator: ExecutableContextErrorMessageCreator): this {
     this.errorMessageCreator = errorMessageCreator;
     return this;
@@ -233,10 +233,16 @@ class ValidatorBuilder {
     return this;
   }
 
+  public withTypeValidator(typeValidator: TypeValidator): this {
+    this.typeValidator = typeValidator;
+    return this;
+  }
+
   public build(): ContextualExecutableValidator {
     return new ContextualExecutableValidator(
       this.errorContext,
       this.errorMessageCreator,
+      this.typeValidator,
     );
   }
 }
diff --git a/tests/unit/application/Parser/ScriptingDefinition/ScriptingDefinitionParser.spec.ts b/tests/unit/application/Parser/ScriptingDefinition/ScriptingDefinitionParser.spec.ts
index 5c7878a3..ab54700f 100644
--- a/tests/unit/application/Parser/ScriptingDefinition/ScriptingDefinitionParser.spec.ts
+++ b/tests/unit/application/Parser/ScriptingDefinition/ScriptingDefinitionParser.spec.ts
@@ -1,32 +1,52 @@
 import { describe, it, expect } from 'vitest';
 import { ScriptingLanguage } from '@/domain/ScriptingLanguage';
-import { ScriptingDefinitionParser } from '@/application/Parser/ScriptingDefinition/ScriptingDefinitionParser';
-import type { IEnumParser } from '@/application/Common/Enum';
+import type { EnumParser } from '@/application/Common/Enum';
 import type { ICodeSubstituter } from '@/application/Parser/ScriptingDefinition/ICodeSubstituter';
 import type { IScriptingDefinition } from '@/domain/IScriptingDefinition';
 import { ProjectDetailsStub } from '@tests/unit/shared/Stubs/ProjectDetailsStub';
 import { EnumParserStub } from '@tests/unit/shared/Stubs/EnumParserStub';
 import { ScriptingDefinitionDataStub } from '@tests/unit/shared/Stubs/ScriptingDefinitionDataStub';
 import { CodeSubstituterStub } from '@tests/unit/shared/Stubs/CodeSubstituterStub';
+import { parseScriptingDefinition } from '@/application/Parser/ScriptingDefinition/ScriptingDefinitionParser';
+import type { ObjectAssertion, TypeValidator } from '@/application/Parser/Common/TypeValidator';
+import { TypeValidatorStub } from '@tests/unit/shared/Stubs/TypeValidatorStub';
+import type { ScriptingDefinitionData } from '@/application/collections/';
+import type { ProjectDetails } from '@/domain/Project/ProjectDetails';
 
 describe('ScriptingDefinitionParser', () => {
   describe('parseScriptingDefinition', () => {
+    it('validates data', () => {
+      // arrange
+      const data = new ScriptingDefinitionDataStub();
+      const expectedAssertion: ObjectAssertion<ScriptingDefinitionData> = {
+        value: data,
+        valueName: 'scripting definition',
+        allowedProperties: ['language', 'fileExtension', 'startCode', 'endCode'],
+      };
+      const validatorStub = new TypeValidatorStub();
+      const context = new TestContext()
+        .withTypeValidator(validatorStub)
+        .withData(data);
+      // act
+      context.parseScriptingDefinition();
+      // assert
+      validatorStub.assertObject(expectedAssertion);
+    });
     describe('language', () => {
       it('parses as expected', () => {
         // arrange
         const expectedLanguage = ScriptingLanguage.batchfile;
         const languageText = 'batchfile';
         const expectedName = 'language';
-        const projectDetails = new ProjectDetailsStub();
         const definition = new ScriptingDefinitionDataStub()
           .withLanguage(languageText);
         const parserMock = new EnumParserStub<ScriptingLanguage>()
           .setup(expectedName, languageText, expectedLanguage);
-        const sut = new ScriptingDefinitionParserBuilder()
+        const context = new TestContext()
           .withParser(parserMock)
-          .build();
+          .withData(definition);
         // act
-        const actual = sut.parse(definition, projectDetails);
+        const actual = context.parseScriptingDefinition();
         // assert
         expect(actual.language).to.equal(expectedLanguage);
       });
@@ -35,56 +55,92 @@ describe('ScriptingDefinitionParser', () => {
       // arrange
       const code = 'hello';
       const expected = 'substituted';
-      const testCases = [
+      const testScenarios: readonly {
+        readonly description: string;
+        getActualValue(result: IScriptingDefinition): string;
+        readonly data: ScriptingDefinitionData;
+      }[] = [
         {
-          name: 'startCode',
+          description: 'startCode',
           getActualValue: (result: IScriptingDefinition) => result.startCode,
           data: new ScriptingDefinitionDataStub()
             .withStartCode(code),
         },
         {
-          name: 'endCode',
+          description: 'endCode',
           getActualValue: (result: IScriptingDefinition) => result.endCode,
           data: new ScriptingDefinitionDataStub()
             .withEndCode(code),
         },
       ];
-      for (const testCase of testCases) {
-        it(testCase.name, () => {
+      testScenarios.forEach(({
+        description, data, getActualValue,
+      }) => {
+        it(description, () => {
           const projectDetails = new ProjectDetailsStub();
           const substituterMock = new CodeSubstituterStub()
             .setup(code, projectDetails, expected);
-          const sut = new ScriptingDefinitionParserBuilder()
-            .withSubstituter(substituterMock)
-            .build();
+          const context = new TestContext()
+            .withData(data)
+            .withProjectDetails(projectDetails)
+            .withSubstituter(substituterMock);
           // act
-          const definition = sut.parse(testCase.data, projectDetails);
+          const definition = context.parseScriptingDefinition();
           // assert
-          const actual = testCase.getActualValue(definition);
+          const actual = getActualValue(definition);
           expect(actual).to.equal(expected);
         });
-      }
+      });
     });
   });
 });
 
-class ScriptingDefinitionParserBuilder {
-  private languageParser: IEnumParser<ScriptingLanguage> = new EnumParserStub<ScriptingLanguage>()
+class TestContext {
+  private languageParser: EnumParser<ScriptingLanguage> = new EnumParserStub<ScriptingLanguage>()
     .setupDefaultValue(ScriptingLanguage.shellscript);
 
   private codeSubstituter: ICodeSubstituter = new CodeSubstituterStub();
 
-  public withParser(parser: IEnumParser<ScriptingLanguage>) {
+  private validator: TypeValidator = new TypeValidatorStub();
+
+  private data: ScriptingDefinitionData = new ScriptingDefinitionDataStub();
+
+  private projectDetails: ProjectDetails = new ProjectDetailsStub();
+
+  public withData(data: ScriptingDefinitionData): this {
+    this.data = data;
+    return this;
+  }
+
+  public withProjectDetails(projectDetails: ProjectDetails): this {
+    this.projectDetails = projectDetails;
+    return this;
+  }
+
+  public withParser(parser: EnumParser<ScriptingLanguage>): this {
     this.languageParser = parser;
     return this;
   }
 
-  public withSubstituter(substituter: ICodeSubstituter) {
+  public withSubstituter(substituter: ICodeSubstituter): this {
     this.codeSubstituter = substituter;
     return this;
   }
 
-  public build() {
-    return new ScriptingDefinitionParser(this.languageParser, this.codeSubstituter);
+  public withTypeValidator(validator: TypeValidator): this {
+    this.validator = validator;
+    return this;
+  }
+
+  public parseScriptingDefinition() {
+    return parseScriptingDefinition(
+      this.data,
+      this.projectDetails,
+      {
+        languageParser: this.languageParser,
+        codeSubstituter: this.codeSubstituter,
+        validator: this.validator,
+      },
+    );
   }
 }
diff --git a/tests/unit/domain/CategoryCollection.spec.ts b/tests/unit/domain/CategoryCollection.spec.ts
index 09497d21..b19d2fa5 100644
--- a/tests/unit/domain/CategoryCollection.spec.ts
+++ b/tests/unit/domain/CategoryCollection.spec.ts
@@ -318,6 +318,10 @@ class CategoryCollectionBuilder {
   }
 
   public construct(): CategoryCollection {
-    return new CategoryCollection(this.os, this.actions, this.scriptingDefinition);
+    return new CategoryCollection({
+      os: this.os,
+      actions: this.actions,
+      scripting: this.scriptingDefinition,
+    });
   }
 }
diff --git a/tests/unit/shared/Stubs/CategoryCollectionFactoryStub.ts b/tests/unit/shared/Stubs/CategoryCollectionFactoryStub.ts
new file mode 100644
index 00000000..ee22b72b
--- /dev/null
+++ b/tests/unit/shared/Stubs/CategoryCollectionFactoryStub.ts
@@ -0,0 +1,23 @@
+import type { CategoryCollectionFactory } from '@/application/Parser/CategoryCollectionParser';
+import type { CategoryCollectionInitParameters } from '@/domain/CategoryCollection';
+import type { ICategoryCollection } from '@/domain/ICategoryCollection';
+import { CategoryCollectionStub } from './CategoryCollectionStub';
+
+export function createCategoryCollectionFactorySpy(): {
+  readonly categoryCollectionFactorySpy: CategoryCollectionFactory;
+  getInitParameters: (
+    category: ICategoryCollection,
+  ) => CategoryCollectionInitParameters | undefined;
+} {
+  const createdCategoryCollections = new Map<
+  ICategoryCollection, CategoryCollectionInitParameters
+  >();
+  return {
+    categoryCollectionFactorySpy: (parameters) => {
+      const categoryCollection = new CategoryCollectionStub();
+      createdCategoryCollections.set(categoryCollection, parameters);
+      return categoryCollection;
+    },
+    getInitParameters: (category) => createdCategoryCollections.get(category),
+  };
+}
diff --git a/tests/unit/shared/Stubs/CategoryCollectionParserStub.ts b/tests/unit/shared/Stubs/CategoryCollectionParserStub.ts
index e9e34c20..436ed9c9 100644
--- a/tests/unit/shared/Stubs/CategoryCollectionParserStub.ts
+++ b/tests/unit/shared/Stubs/CategoryCollectionParserStub.ts
@@ -2,8 +2,8 @@ import type { ProjectDetails } from '@/domain/Project/ProjectDetails';
 import type { ICategoryCollection } from '@/domain/ICategoryCollection';
 import { getEnumValues } from '@/application/Common/Enum';
 import type { CollectionData } from '@/application/collections/';
-import type { CategoryCollectionParserType } from '@/application/Parser/ApplicationParser';
 import { OperatingSystem } from '@/domain/OperatingSystem';
+import type { CategoryCollectionParser } from '@/application/Parser/CategoryCollectionParser';
 import { CategoryCollectionStub } from './CategoryCollectionStub';
 
 export class CategoryCollectionParserStub {
@@ -22,7 +22,7 @@ export class CategoryCollectionParserStub {
     return this;
   }
 
-  public getStub(): CategoryCollectionParserType {
+  public getStub(): CategoryCollectionParser {
     return (data: CollectionData, projectDetails: ProjectDetails): ICategoryCollection => {
       this.arguments.push({ data, projectDetails });
       const foundReturnValue = this.returnValues.get(data);
diff --git a/tests/unit/shared/Stubs/CategoryParserStub.ts b/tests/unit/shared/Stubs/CategoryParserStub.ts
new file mode 100644
index 00000000..ce41b016
--- /dev/null
+++ b/tests/unit/shared/Stubs/CategoryParserStub.ts
@@ -0,0 +1,34 @@
+import type { CategoryParser } from '@/application/Parser/Executable/CategoryParser';
+import type { CategoryData } from '@/application/collections/';
+import type { Category } from '@/domain/Executables/Category/Category';
+import type { CategoryCollectionSpecificUtilities } from '@/application/Parser/Executable/CategoryCollectionSpecificUtilities';
+import { CategoryStub } from './CategoryStub';
+
+export class CategoryParserStub {
+  private configuredParseResults = new Map<CategoryData, Category>();
+
+  private usedUtilities = new Array<CategoryCollectionSpecificUtilities>();
+
+  public get(): CategoryParser {
+    return (category, utilities) => {
+      const result = this.configuredParseResults.get(category);
+      this.usedUtilities.push(utilities);
+      if (result) {
+        return result;
+      }
+      return new CategoryStub(5489);
+    };
+  }
+
+  public withConfiguredParseResult(
+    givenCategory: CategoryData,
+    parsedCategory: Category,
+  ): this {
+    this.configuredParseResults.set(givenCategory, parsedCategory);
+    return this;
+  }
+
+  public getUsedUtilities(): readonly CategoryCollectionSpecificUtilities[] {
+    return this.usedUtilities;
+  }
+}
diff --git a/tests/unit/shared/Stubs/EnumParserStub.ts b/tests/unit/shared/Stubs/EnumParserStub.ts
index 84a60d17..1afe1e44 100644
--- a/tests/unit/shared/Stubs/EnumParserStub.ts
+++ b/tests/unit/shared/Stubs/EnumParserStub.ts
@@ -1,17 +1,17 @@
-import type { IEnumParser } from '@/application/Common/Enum';
+import type { EnumParser } from '@/application/Common/Enum';
 
-export class EnumParserStub<T> implements IEnumParser<T> {
+export class EnumParserStub<T> implements EnumParser<T> {
   private readonly scenarios = new Array<{
     inputName: string, inputValue: string, outputValue: T }>();
 
   private defaultValue: T;
 
-  public setup(inputName: string, inputValue: string, outputValue: T) {
+  public setup(inputName: string, inputValue: string, outputValue: T): this {
     this.scenarios.push({ inputName, inputValue, outputValue });
     return this;
   }
 
-  public setupDefaultValue(outputValue: T) {
+  public setupDefaultValue(outputValue: T): this {
     this.defaultValue = outputValue;
     return this;
   }
diff --git a/tests/unit/shared/Stubs/ErrorWithContextWrapperStub.ts b/tests/unit/shared/Stubs/ErrorWithContextWrapperStub.ts
index 10aadeae..89d5afeb 100644
--- a/tests/unit/shared/Stubs/ErrorWithContextWrapperStub.ts
+++ b/tests/unit/shared/Stubs/ErrorWithContextWrapperStub.ts
@@ -1,4 +1,4 @@
-import type { ErrorWithContextWrapper } from '@/application/Parser/ContextualError';
+import type { ErrorWithContextWrapper } from '@/application/Parser/Common/ContextualError';
 
 export const errorWithContextWrapperStub
 : ErrorWithContextWrapper = (error, message) => new Error(`[stubbed error wrapper] ${error.message} + ${message}`);
diff --git a/tests/unit/shared/Stubs/ErrorWrapperStub.ts b/tests/unit/shared/Stubs/ErrorWrapperStub.ts
index 080d5b37..8cde78cd 100644
--- a/tests/unit/shared/Stubs/ErrorWrapperStub.ts
+++ b/tests/unit/shared/Stubs/ErrorWrapperStub.ts
@@ -1,4 +1,4 @@
-import type { ErrorWithContextWrapper } from '@/application/Parser/ContextualError';
+import type { ErrorWithContextWrapper } from '@/application/Parser/Common/ContextualError';
 
 export class ErrorWrapperStub {
   private errorToReturn: Error | undefined;
diff --git a/tests/unit/shared/Stubs/ExecutableValidatorStub.ts b/tests/unit/shared/Stubs/ExecutableValidatorStub.ts
index fc0d846d..201b2801 100644
--- a/tests/unit/shared/Stubs/ExecutableValidatorStub.ts
+++ b/tests/unit/shared/Stubs/ExecutableValidatorStub.ts
@@ -1,5 +1,5 @@
-import type { ExecutableData } from '@/application/collections/';
 import type { ExecutableValidator, ExecutableValidatorFactory } from '@/application/Parser/Executable/Validation/ExecutableValidator';
+import type { TypeValidator } from '@/application/Parser/Common/TypeValidator';
 import { StubWithObservableMethodCalls } from './StubWithObservableMethodCalls';
 
 export const createExecutableValidatorFactoryStub
@@ -23,10 +23,10 @@ export class ExecutableValidatorStub
     return this;
   }
 
-  public assertDefined(data: ExecutableData): this {
+  public assertType(assert: (validator: TypeValidator) => void): this {
     this.registerMethodCall({
-      methodName: 'assertDefined',
-      args: [data],
+      methodName: 'assertType',
+      args: [assert],
     });
     return this;
   }
diff --git a/tests/unit/shared/Stubs/TypeValidatorStub.ts b/tests/unit/shared/Stubs/TypeValidatorStub.ts
new file mode 100644
index 00000000..b84ce673
--- /dev/null
+++ b/tests/unit/shared/Stubs/TypeValidatorStub.ts
@@ -0,0 +1,45 @@
+import type { NonEmptyCollectionAssertion, ObjectAssertion, TypeValidator } from '@/application/Parser/Common/TypeValidator';
+import type { FunctionKeys } from '@/TypeHelpers';
+import { expectDeepIncludes } from '@tests/shared/Assertions/ExpectDeepIncludes';
+import { StubWithObservableMethodCalls } from './StubWithObservableMethodCalls';
+
+export type UnknownObjectAssertion = ObjectAssertion<unknown>;
+
+export class TypeValidatorStub
+  extends StubWithObservableMethodCalls<TypeValidator>
+  implements TypeValidator {
+  public assertObject<T>(assertion: ObjectAssertion<T>): void {
+    this.registerMethodCall({
+      methodName: 'assertObject',
+      args: [assertion as UnknownObjectAssertion],
+    });
+  }
+
+  public assertNonEmptyCollection(assertion: NonEmptyCollectionAssertion): void {
+    this.registerMethodCall({
+      methodName: 'assertNonEmptyCollection',
+      args: [assertion],
+    });
+  }
+
+  public expectObjectAssertion<T>(
+    expectedAssertion: ObjectAssertion<T>,
+  ): void {
+    this.expectAssertion('assertObject', expectedAssertion as UnknownObjectAssertion);
+  }
+
+  public expectNonEmptyCollectionAssertion(
+    expectedAssertion: NonEmptyCollectionAssertion,
+  ): void {
+    this.expectAssertion('assertNonEmptyCollection', expectedAssertion);
+  }
+
+  private expectAssertion<T extends FunctionKeys<TypeValidator>>(
+    methodName: T,
+    expectedAssertion: Parameters<TypeValidator[T]>[0],
+  ): void {
+    const assertionCalls = this.callHistory.filter((c) => c.methodName === methodName);
+    const assertionArgs = assertionCalls.map((c) => c.args[0]);
+    expectDeepIncludes(assertionArgs, expectedAssertion);
+  }
+}