diff --git a/.changelog/20250707143504_ck_18777_add_rule_to_validate_changelog_entry.md b/.changelog/20250707143504_ck_18777_add_rule_to_validate_changelog_entry.md
new file mode 100644
index 0000000..3285989
--- /dev/null
+++ b/.changelog/20250707143504_ck_18777_add_rule_to_validate_changelog_entry.md
@@ -0,0 +1,7 @@
+---
+type: Feature
+scope: eslint-plugin-ckeditor5-rules
+closes: https://github.com/ckeditor/ckeditor5/issues/18777
+---
+
+Add the `validate-changelog-entry` rule for validating Markdown-based changelog entries.
diff --git a/.circleci/config.yml b/.circleci/config.yml
index 6a08787..9ab18a0 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -80,7 +80,8 @@ commands:
 
 jobs:
   notify_ci_failure:
-    machine: true
+    docker:
+      - image: cimg/node:22.12.0
     parameters:
       hideAuthor:
         type: string
@@ -108,7 +109,8 @@ jobs:
           no_output_timeout: 1h
 
   validate_and_tests:
-    machine: true
+    docker:
+      - image: cimg/node:22.12.0
     steps:
       - checkout
       - bootstrap_repository_command
@@ -120,7 +122,8 @@ jobs:
           command: yarn run test
 
   release_prepare:
-    machine: true
+    docker:
+      - image: cimg/node:22.12.0
     steps:
       - checkout
       - bootstrap_repository_command
@@ -129,7 +132,8 @@ jobs:
           command: yarn run release:prepare-packages --verbose --compile-only
 
   trigger_release_process:
-    machine: true
+    docker:
+      - image: cimg/node:22.12.0
     steps:
       - checkout
       - bootstrap_repository_command
@@ -153,7 +157,8 @@ jobs:
           command: yarn ckeditor5-dev-ci-trigger-circle-build
 
   release_project:
-    machine: true
+    docker:
+      - image: cimg/node:22.12.0
     steps:
       - checkout
       - bootstrap_repository_command
diff --git a/eslint.config.mjs b/eslint.config.mjs
index a4044ae..b7bfb4d 100644
--- a/eslint.config.mjs
+++ b/eslint.config.mjs
@@ -3,11 +3,18 @@
  * For licensing, see LICENSE.md.
  */
 
+import fs from 'fs';
+import path from 'path';
 import globals from 'globals';
 import { defineConfig } from 'eslint/config';
 import ckeditor5Config from 'eslint-config-ckeditor5';
 import ckeditor5Rules from 'eslint-plugin-ckeditor5-rules';
 
+const projectPackages = fs
+	.readdirSync( path.resolve( import.meta.dirname, 'packages' ), { withFileTypes: true } )
+	.filter( dirent => dirent.isDirectory() )
+	.map( dirent => dirent.name );
+
 export default defineConfig( [
 	{
 		extends: ckeditor5Config,
@@ -40,5 +47,21 @@ export default defineConfig( [
 				]
 			} ]
 		}
+	},
+	{
+		files: [ '.changelog/**/*.md' ],
+		plugins: {
+			'ckeditor5-rules': ckeditor5Rules
+		},
+		language: 'markdown/gfm',
+		languageOptions: {
+			frontmatter: 'yaml'
+		},
+		rules: {
+			'ckeditor5-rules/validate-changelog-entry': [ 'error', {
+				allowedScopes: projectPackages,
+				repositoryType: 'mono'
+			} ]
+		}
 	}
 ] );
diff --git a/packages/eslint-config-ckeditor5/eslint.config.mjs b/packages/eslint-config-ckeditor5/eslint.config.mjs
index 724edd8..26876be 100644
--- a/packages/eslint-config-ckeditor5/eslint.config.mjs
+++ b/packages/eslint-config-ckeditor5/eslint.config.mjs
@@ -7,6 +7,7 @@ import globals from 'globals';
 import { defineConfig } from 'eslint/config';
 import js from '@eslint/js';
 import ts from 'typescript-eslint';
+import markdown from '@eslint/markdown';
 import mocha from 'eslint-plugin-mocha';
 import stylistic from '@stylistic/eslint-plugin';
 import ckeditor5Rules from 'eslint-plugin-ckeditor5-rules';
@@ -24,6 +25,8 @@ const rulesGeneral = [
 			ecmaVersion: 2020,
 			sourceType: 'module'
 		},
+		
+		files: [ '**/*.@(js|ts|tsx)' ],
 
 		rules: {
 			/*
@@ -482,10 +485,27 @@ const rulesDocs = [
 	}
 ];
 
+const rulesChangelog = [
+	{
+		files: [ '**/*.md' ],
+
+		plugins: {
+			markdown
+		},
+
+		language: 'markdown/gfm',
+
+		languageOptions: {
+			frontmatter: 'yaml'
+		}
+	}
+];
+
 export default defineConfig( [
 	rulesGeneral,
 	rulesTypeScript,
 	rulesSourceCode,
 	rulesTests,
-	rulesDocs
+	rulesDocs,
+	rulesChangelog
 ] );
diff --git a/packages/eslint-config-ckeditor5/package.json b/packages/eslint-config-ckeditor5/package.json
index ff94f6a..fbaae54 100644
--- a/packages/eslint-config-ckeditor5/package.json
+++ b/packages/eslint-config-ckeditor5/package.json
@@ -26,6 +26,7 @@
   },
   "dependencies": {
     "@eslint/js": "^9.26.0",
+    "@eslint/markdown": "^6.6.0",
     "@stylistic/eslint-plugin": "^4.2.0",
     "eslint-plugin-ckeditor5-rules": "^11.0.1",
     "eslint-plugin-mocha": "^11.0.0",
diff --git a/packages/eslint-plugin-ckeditor5-rules/lib/index.js b/packages/eslint-plugin-ckeditor5-rules/lib/index.js
index 9618093..2a5b282 100644
--- a/packages/eslint-plugin-ckeditor5-rules/lib/index.js
+++ b/packages/eslint-plugin-ckeditor5-rules/lib/index.js
@@ -23,6 +23,7 @@ module.exports = {
 		'allow-svg-imports-only-in-icons-package': require( './rules/allow-svg-imports-only-in-icons-package.js' ),
 		'prevent-license-key-leak': require( './rules/prevent-license-key-leak' ),
 		'require-as-const-returns-in-methods': require( './rules/require-as-const-returns-in-methods' ),
-		'require-file-extensions-in-imports': require( './rules/require-file-extensions-in-imports' )
+		'require-file-extensions-in-imports': require( './rules/require-file-extensions-in-imports' ),
+		'validate-changelog-entry': require( './rules/validate-changelog-entry' )
 	}
 };
diff --git a/packages/eslint-plugin-ckeditor5-rules/lib/rules/validate-changelog-entry.js b/packages/eslint-plugin-ckeditor5-rules/lib/rules/validate-changelog-entry.js
new file mode 100644
index 0000000..a4cca89
--- /dev/null
+++ b/packages/eslint-plugin-ckeditor5-rules/lib/rules/validate-changelog-entry.js
@@ -0,0 +1,308 @@
+/**
+ * @license Copyright (c) 2003-2025, CKSource Holding sp. z o.o. All rights reserved.
+ * For licensing, see LICENSE.md.
+ */
+
+'use strict';
+
+const yaml = require( 'yaml' );
+
+const ALLOWED_TYPES = {
+	single: [
+		'feature',
+		'fix',
+		'other',
+		'breaking change'
+	],
+	mono: [
+		'feature',
+		'fix',
+		'other',
+		'major breaking change',
+		'minor breaking change'
+	]
+};
+
+const placeholderTexts = [
+	'Required concise and meaningful summary of the change.',
+	'Optional additional context or rationale.',
+	'Remove if not needed.'
+];
+
+const ISSUE_SLUG_PATTERN = /^[a-z0-9.-]+\/[a-z0-9.-]+#\d+$/;
+const ISSUE_PATTERN = /^\d+$/;
+const ISSUE_URL_PATTERN = /^https:\/\/github\.com\/[a-z0-9.-]+\/[a-z0-9.-]+\/issues\/\d+$/;
+const NICK_NAME_PATTERN = /^(@?)[a-z0-9-_]+$/i;
+
+module.exports = {
+	meta: {
+		type: 'problem',
+		docs: {
+			description: 'Validate changelog entries.',
+			category: 'CKEditor5',
+			url: 'https://ckeditor.com/docs/ckeditor5/latest/framework/contributing/code-style.html#valid-changelog-entries'
+		},
+		schema: [
+			{
+				type: 'object',
+				additionalProperties: false,
+				properties: {
+					allowedScopes: {
+						type: 'array',
+						items: {
+							type: 'string'
+						}
+					},
+
+					repositoryType: {
+						type: 'string',
+						enum: [ 'single', 'mono' ]
+					}
+				},
+				required: [ 'repositoryType' ]
+			}
+		],
+		messages: {
+			'missingChangeData': 'Changelog entry must include a YAML frontmatter.',
+			'missingChangeSummary': 'Changelog entry must include a text summary.',
+			'missingTypeField': 'Changelog entry must include a \'type\' field.',
+			'invalidField': 'Invalid \'{{ kind }}\' value: \'{{ value }}\'.',
+			'scopesInSingleRepository': 'Changelog entry for a single repository must not include the \'scopes\' field.',
+			'defaultChangeSummary': 'Replace the default placeholder text with a meaningful summary.'
+		}
+	},
+
+	create( context ) {
+		const options = context.options[ 0 ];
+		let hasFrontmatter = false;
+		let hasText = false;
+
+		return {
+			text( node ) {
+				hasText ||= true;
+
+				if ( placeholderTexts.includes( node.value.trim() ) ) {
+					return context.report( {
+						node,
+						messageId: 'defaultChangeSummary'
+					} );
+				}
+			},
+
+			yaml( node ) {
+				hasFrontmatter ||= true;
+
+				const lineCounter = new yaml.LineCounter();
+				const doc = yaml.parseDocument( node.value, {
+					lineCounter
+				} );
+
+				const getKey = key => doc.contents?.items?.find( item => item.key.value === key );
+
+				[
+					...validateType( getKey( 'type' ), options ),
+					...validateScopes( getKey( 'scope' ), options ),
+					...validateCloses( getKey( 'closes' ) ),
+					...validateSee( getKey( 'see' ) ),
+					...validateCommunityCredits( getKey( 'communityCredits' ) )
+				]
+					.forEach( ( { range, ...error } ) => {
+						const lineOffset = node.position.start.line;
+						const start = lineCounter.linePos( range[ 0 ] );
+						const end = lineCounter.linePos( range[ 1 ] );
+
+						context.report( {
+							...error,
+							loc: {
+								start: {
+									line: lineOffset + start.line,
+									column: start.col
+								},
+								end: {
+									line: lineOffset + end.line,
+									column: end.col
+								}
+							}
+						} );
+					} );
+			},
+
+			'root:exit'( node ) {
+				if ( !hasFrontmatter ) {
+					// If frontmatter data is missing, display an error at the beginning of the file.
+					context.report( {
+						node: context.getSourceCode().ast,
+						messageId: 'missingChangeData',
+						loc: {
+							start: {
+								line: node.position.start.line,
+								column: node.position.start.column
+							},
+							end: {
+								line: node.position.start.line,
+								column: node.position.start.column
+							}
+						}
+					} );
+				}
+
+				if ( !hasText ) {
+					// If text summary is missing, display an error at the end of the file.
+					context.report( {
+						node: context.getSourceCode().ast,
+						messageId: 'missingChangeSummary',
+						loc: {
+							start: {
+								line: node.position.end.line,
+								column: node.position.end.column
+							},
+							end: {
+								line: node.position.end.line,
+								column: node.position.end.column
+							}
+						}
+					} );
+				}
+			}
+		};
+	}
+};
+
+/**
+ * Validates the "type" field of a changelog entry.
+ */
+function validateType( type, options ) {
+	if ( !type ) {
+		return [
+			{
+				messageId: 'missingTypeField',
+				range: [ 0, 0 ]
+			}
+		];
+	}
+
+	const { source, range } = type.value;
+
+	if ( ALLOWED_TYPES[ options.repositoryType ].includes( source.toLowerCase() ) ) {
+		return [];
+	}
+
+	return [
+		{
+			messageId: 'invalidField',
+			data: {
+				kind: 'type',
+				value: source
+			},
+			range
+		}
+	];
+}
+
+/**
+ * Validates the "scopes" field of a changelog entry.
+ */
+function validateScopes( scopes, options ) {
+	if ( !scopes ) {
+		return [];
+	}
+
+	const normalized = toArray( scopes ).filter( scope => !!scope.source );
+
+	if ( normalized.length && options.repositoryType === 'single' ) {
+		return [
+			{
+				messageId: 'scopesInSingleRepository',
+				range: scopes.key.range
+			}
+		];
+	}
+
+	return normalized.reduce( ( errors, scope ) => {
+		if ( !options.allowedScopes.includes( scope.source ) ) {
+			errors.push( {
+				messageId: 'invalidField',
+				data: {
+					kind: 'scope',
+					value: scope.source
+				},
+				range: scope.range
+			} );
+		}
+
+		return errors;
+	}, [] );
+}
+
+/**
+ * Validates field containing issue in a changelog entry.
+ */
+function validateIssue( issue, kind ) {
+	if ( !issue ) {
+		return [];
+	}
+
+	return toArray( issue )
+		.filter( issue => !!issue.source )
+		.reduce( ( errors, issue ) => {
+			if ( !ISSUE_SLUG_PATTERN.test( issue ) && !ISSUE_PATTERN.test( issue ) && !ISSUE_URL_PATTERN.test( issue ) ) {
+				errors.push( {
+					messageId: 'invalidField',
+					data: {
+						kind,
+						value: issue.source
+					},
+					range: issue.range
+				} );
+			}
+
+			return errors;
+		}, [] );
+}
+
+/**
+ * Validates the "closes" field of a changelog entry.
+ */
+function validateCloses( issue ) {
+	return validateIssue( issue, 'closes' );
+}
+
+/**
+ * Validates the "see" field of a changelog entry.
+ */
+function validateSee( issue ) {
+	return validateIssue( issue, 'see' );
+}
+
+/**
+ * Validates the "communityCredits" field of a changelog entry.
+ */
+function validateCommunityCredits( communityCredits ) {
+	if ( !communityCredits ) {
+		return [];
+	}
+
+	return toArray( communityCredits )
+		.filter( issue => !!issue.source )
+		.reduce( ( errors, credit ) => {
+			if ( !NICK_NAME_PATTERN.test( credit ) ) {
+				errors.push( {
+					messageId: 'invalidField',
+					data: {
+						kind: 'communityCredits',
+						value: credit.source
+					},
+					range: credit.range
+				} );
+			}
+
+			return errors;
+		}, [] );
+}
+
+/**
+ * Ensures that the given pair is an array.
+ */
+function toArray( pair ) {
+	return pair.value.items ?? [ pair.value ];
+}
diff --git a/packages/eslint-plugin-ckeditor5-rules/package.json b/packages/eslint-plugin-ckeditor5-rules/package.json
index 41dfc49..85c6f8c 100644
--- a/packages/eslint-plugin-ckeditor5-rules/package.json
+++ b/packages/eslint-plugin-ckeditor5-rules/package.json
@@ -33,9 +33,12 @@
     "fs-extra": "^11.1.1",
     "resolve.exports": "^2.0.2",
     "upath": "^2.0.1",
-    "validate-npm-package-name": "^6.0.0"
+    "validate-npm-package-name": "^6.0.0",
+    "yaml": "^2.8.0"
   },
   "devDependencies": {
+    "@eslint/markdown": "^6.6.0",
+    "dedent": "^1.6.0",
     "eslint": "^9.26.0",
     "glob": "^11.0.2",
     "lodash": "^4.17.21",
diff --git a/packages/eslint-plugin-ckeditor5-rules/tests/rules/validate-changelog-entry.mjs b/packages/eslint-plugin-ckeditor5-rules/tests/rules/validate-changelog-entry.mjs
new file mode 100644
index 0000000..6081470
--- /dev/null
+++ b/packages/eslint-plugin-ckeditor5-rules/tests/rules/validate-changelog-entry.mjs
@@ -0,0 +1,528 @@
+/**
+ * @license Copyright (c) 2003-2025, CKSource Holding sp. z o.o. All rights reserved.
+ * For licensing, see LICENSE.md.
+ */
+
+'use strict';
+
+import rule from '../../lib/rules/validate-changelog-entry.js';
+import dedent from 'dedent';
+import { RuleTester } from 'eslint';
+import markdown from '@eslint/markdown';
+
+const ruleTester = new RuleTester( {
+	plugins: {
+		markdown
+	},
+	language: 'markdown/gfm',
+	languageOptions: {
+		frontmatter: 'yaml'
+	}
+} );
+
+ruleTester.run( 'eslint-plugin-ckeditor5-rules/validate-changelog-entry', rule, {
+	valid: [
+		// Single repository with only the "type" field.
+		{
+			code: dedent`
+			---
+			type: feature
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'single' } ]
+		},
+
+		// Mono repository with only the "type" field.
+		{
+			code: dedent`
+			---
+			type: feature
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+
+		// Uses "type: fix".
+		{
+			code: dedent`
+			---
+			type: fix
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'single' } ]
+		},
+		{
+			code: dedent`
+			---
+			type: fix
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+
+		// Uses "type: other".
+		{
+			code: dedent`
+			---
+			type: other
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'single' } ]
+		},
+		{
+			code: dedent`
+			---
+			type: other
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+
+		// Uses "type: breaking change" in single repository.
+		{
+			code: dedent`
+			---
+			type: breaking change
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'single' } ]
+		},
+
+		// Uses "type: major breaking change" in mono repository.
+		{
+			code: dedent`
+			---
+			type: major breaking change
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+
+		// Uses "type: minor breaking change" in mono repository.
+		{
+			code: dedent`
+			---
+			type: minor breaking change
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+
+		// Uses allowed "scope" field.
+		{
+			code: dedent`
+			---
+			type: feature
+			scope:
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono', allowedScopes: [ 'test' ] } ]
+		},
+		{
+			code: dedent`
+			---
+			type: feature
+			scope:
+			 -
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono', allowedScopes: [ 'test' ] } ]
+		},
+		{
+			code: dedent`
+			---
+			type: feature
+			scope: test
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono', allowedScopes: [ 'test' ] } ]
+		},
+		{
+			code: dedent`
+			---
+			type: feature
+			scope:
+			 - test
+			 - test2
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono', allowedScopes: [ 'test', 'test2' ] } ]
+		},
+
+		// Uses valid "closes" field.
+		{
+			code: dedent`
+			---
+			type: feature
+			closes:
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+		{
+			code: dedent`
+			---
+			type: feature
+			closes:
+			 -
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+		{
+			code: dedent`
+			---
+			type: feature
+			closes: 123
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+		{
+			code: dedent`
+			---
+			type: feature
+			closes:
+			 - 123
+			 - ckeditor/ckeditor5#123
+			 - https://github.com/ckeditor/ckeditor5/issues/18777
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+
+		// Uses valid "see" field.
+		{
+			code: dedent`
+			---
+			type: feature
+			see:
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+		{
+			code: dedent`
+			---
+			type: feature
+			see:
+			 -
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+		{
+			code: dedent`
+			---
+			type: feature
+			see: 123
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+		{
+			code: dedent`
+			---
+			type: feature
+			see:
+			 - 123
+			 - ckeditor/ckeditor5#123
+			 - https://github.com/ckeditor/ckeditor5/issues/18777
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+
+		// Uses valid "communityCredits" field.
+		{
+			code: dedent`
+			---
+			type: feature
+			communityCredits:
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+		{
+			code: dedent`
+			---
+			type: feature
+			communityCredits:
+			 -
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+		{
+			code: dedent`
+			---
+			type: feature
+			communityCredits: user
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+		{
+			code: dedent`
+			---
+			type: feature
+			communityCredits:
+			 - user1
+			 - user2
+			 - user3
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ]
+		},
+	],
+
+	invalid: [
+		// Empty file.
+		{
+			code: dedent``,
+			options: [ { repositoryType: 'mono' } ],
+			errors: [
+				'Changelog entry must include a YAML frontmatter.',
+				'Changelog entry must include a text summary.'
+			]
+		},
+
+		// Missing frontmatter.
+		{
+			code: dedent`Changelog summary`,
+			options: [ { repositoryType: 'mono' } ],
+			errors: [
+				'Changelog entry must include a YAML frontmatter.'
+			]
+		},
+
+		// Empty frontmatter.
+		{
+			code: dedent`
+			---
+			---
+			Changelog summary
+			`,
+			options: [ { repositoryType: 'mono' } ],
+			errors: [
+				'Changelog entry must include a \'type\' field.'
+			]
+		},
+
+		// Missing text summary.
+		{
+			code: dedent`
+			---
+			type: feature
+			---
+			`,
+			options: [ { repositoryType: 'mono' } ],
+			errors: [
+				'Changelog entry must include a text summary.'
+			]
+		},
+
+		// Default text summary.
+		{
+			code: dedent`
+			---
+			type: feature
+			---
+
+			Required concise and meaningful summary of the change.
+
+			Optional additional context or rationale. **Remove if not needed.**
+			`,
+			options: [ { repositoryType: 'mono' } ],
+			errors: [
+				'Replace the default placeholder text with a meaningful summary.',
+				'Replace the default placeholder text with a meaningful summary.',
+				'Replace the default placeholder text with a meaningful summary.'
+			]
+		},
+
+		// Invalid "type" field.
+		{
+			code: dedent`
+			---
+			type: test
+			---
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ],
+			errors: [
+				'Invalid \'type\' value: \'test\'.'
+			]
+		},
+
+		// Uses "type: breaking change" in mono repository.
+		{
+			code: dedent`
+			---
+			type: breaking change
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ],
+			errors: [
+				'Invalid \'type\' value: \'breaking change\'.'
+			]
+		},
+
+		// Uses "type: major breaking change" in single repository.
+		{
+			code: dedent`
+			---
+			type: major breaking change
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'single' } ],
+			errors: [
+				'Invalid \'type\' value: \'major breaking change\'.'
+			]
+		},
+
+		// Uses "type: minor breaking change" in single repository.
+		{
+			code: dedent`
+			---
+			type: minor breaking change
+			---
+
+			Change summary.
+			`,
+			options: [ { repositoryType: 'single' } ],
+			errors: [
+				'Invalid \'type\' value: \'minor breaking change\'.'
+			]
+		},
+
+		// Scope in single repository.
+		{
+			code: dedent`
+			---
+			type: feature
+			scope: test
+			---
+			Change summary.
+			`,
+			options: [ { repositoryType: 'single' } ],
+			errors: [
+				'Changelog entry for a single repository must not include the \'scopes\' field.'
+			]
+		},
+
+		// Invalid "scope" field.
+		{
+			code: dedent`
+			---
+			type: feature
+			scope: test
+			---
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono', allowedScopes: [ 'allowed' ] } ],
+			errors: [
+				'Invalid \'scope\' value: \'test\'.'
+			]
+		},
+
+		// Invalid "closes" field.
+		{
+			code: dedent`
+			---
+			type: feature
+			closes: test
+			---
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ],
+			errors: [
+				'Invalid \'closes\' value: \'test\'.'
+			]
+		},
+
+		// Invalid "see" field.
+		{
+			code: dedent`
+			---
+			type: feature
+			see: test
+			---
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ],
+			errors: [
+				'Invalid \'see\' value: \'test\'.'
+			]
+		},
+
+		// Invalid "communityCredits" field.
+		{
+			code: dedent`
+			---
+			type: feature
+			communityCredits: %^&*
+			---
+			Change summary.
+			`,
+			options: [ { repositoryType: 'mono' } ],
+			errors: [
+				'Invalid \'communityCredits\' value: \'%^&*\'.'
+			]
+		},
+	]
+} );