diff --git a/packages/integrations/mdx/test/test-utils.ts b/packages/integrations/mdx/test/test-utils.ts
index 65da8a290573..2f725e8daa22 100644
--- a/packages/integrations/mdx/test/test-utils.ts
+++ b/packages/integrations/mdx/test/test-utils.ts
@@ -2,6 +2,10 @@ import type * as estree from 'estree';
 import type * as hast from 'hast';
 import type * as mdast from 'mdast';
 import type * as unified from 'unified';
+import {
+	AstroIntegrationLogger,
+	type AstroLogMessage,
+} from '../../../astro/dist/core/logger/core.js';
 
 export type RemarkPlugin<PluginParameters extends any[] = any[]> = unified.Plugin<
 	PluginParameters,
@@ -17,3 +21,24 @@ export type RecmaPlugin<PluginParameters extends any[] = any[]> = unified.Plugin
 	PluginParameters,
 	estree.Program
 >;
+
+export class SpyIntegrationLogger extends AstroIntegrationLogger {
+	readonly messages: AstroLogMessage[];
+
+	constructor() {
+		const messages: AstroLogMessage[] = [];
+		super(
+			{
+				destination: {
+					write(chunk): boolean {
+						messages.push(chunk);
+						return true;
+					},
+				},
+				level: 'warn',
+			},
+			'test-spy',
+		);
+		this.messages = messages;
+	}
+}
diff --git a/packages/integrations/mdx/test/units/mdx-compilation.test.ts b/packages/integrations/mdx/test/units/mdx-compilation.test.ts
index c45e9c65dcbe..b723b951cf32 100644
--- a/packages/integrations/mdx/test/units/mdx-compilation.test.ts
+++ b/packages/integrations/mdx/test/units/mdx-compilation.test.ts
@@ -2,14 +2,18 @@ import assert from 'node:assert/strict';
 import { describe, it } from 'node:test';
 import { rehypeHeadingIds } from '@astrojs/markdown-remark';
 import { compile as _compile, type CompileOptions, nodeTypes } from '@mdx-js/mdx';
-import type { AstroIntegrationLogger } from 'astro';
 import { visit as estreeVisit } from 'estree-util-visit';
 import rehypeRaw from 'rehype-raw';
 import remarkGfm from 'remark-gfm';
 import remarkSmartypants from 'remark-smartypants';
 import { visit } from 'unist-util-visit';
 import { ignoreStringPlugins } from '../../dist/utils.js';
-import type { RecmaPlugin, RehypePlugin, RemarkPlugin } from '../test-utils.js';
+import {
+	SpyIntegrationLogger,
+	type RecmaPlugin,
+	type RehypePlugin,
+	type RemarkPlugin,
+} from '../test-utils.ts';
 
 /**
  * Compile MDX to JSX string output for inspection.
@@ -259,7 +263,7 @@ describe('MDX string-based plugin filtering', () => {
 		// When a string-based plugin is provided, the ignoreStringPlugins
 		// function filters it out. We test the filter function directly in utils.test.js.
 		// Here we verify that only function plugins affect output.
-		const logger = { warn() {} } as unknown as AstroIntegrationLogger;
+		const logger = new SpyIntegrationLogger();
 
 		const plugins = ['remark-toc', () => (tree: unknown) => tree];
 		const filtered = ignoreStringPlugins(plugins, logger);
diff --git a/packages/integrations/mdx/test/units/utils.test.ts b/packages/integrations/mdx/test/units/utils.test.ts
index 0973d46699c4..a20db2de1694 100644
--- a/packages/integrations/mdx/test/units/utils.test.ts
+++ b/packages/integrations/mdx/test/units/utils.test.ts
@@ -1,12 +1,13 @@
 import assert from 'node:assert/strict';
 import { describe, it } from 'node:test';
-import type { AstroConfig, AstroIntegrationLogger } from 'astro';
+import type { AstroConfig } from 'astro';
 import {
 	appendForwardSlash,
 	getFileInfo,
 	ignoreStringPlugins,
 	jsToTreeNode,
 } from '../../dist/utils.js';
+import { SpyIntegrationLogger } from '../test-utils.ts';
 
 describe('utils', () => {
 	describe('appendForwardSlash', () => {
@@ -124,30 +125,20 @@ describe('utils', () => {
 	});
 
 	describe('ignoreStringPlugins', () => {
-		function mockLogger(): AstroIntegrationLogger & { warnings: string[] } {
-			const warnings: string[] = [];
-			return {
-				warn: (msg: string) => {
-					warnings.push(msg);
-				},
-				warnings,
-			} as AstroIntegrationLogger & { warnings: string[] };
-		}
-
 		it('returns function plugins unchanged', () => {
 			const plugin1 = () => {};
 			const plugin2 = () => {};
-			const logger = mockLogger();
+			const logger = new SpyIntegrationLogger();
 			const result = ignoreStringPlugins([plugin1, plugin2], logger);
 			assert.equal(result.length, 2);
 			assert.equal(result[0], plugin1);
 			assert.equal(result[1], plugin2);
-			assert.equal(logger.warnings.length, 0);
+			assert.equal(logger.messages.filter((m) => m.level === 'warn').length, 0);
 		});
 
 		it('filters out string-based plugins', () => {
 			const fnPlugin = () => {};
-			const logger = mockLogger();
+			const logger = new SpyIntegrationLogger();
 			const result = ignoreStringPlugins(['remark-toc', fnPlugin], logger);
 			assert.equal(result.length, 1);
 			assert.equal(result[0], fnPlugin);
@@ -155,31 +146,31 @@ describe('utils', () => {
 
 		it('filters out array-based string plugins [string, options]', () => {
 			const fnPlugin = () => {};
-			const logger = mockLogger();
+			const logger = new SpyIntegrationLogger();
 			const result = ignoreStringPlugins([['remark-toc', {}], fnPlugin], logger);
 			assert.equal(result.length, 1);
 			assert.equal(result[0], fnPlugin);
 		});
 
 		it('logs warnings for string plugins', () => {
-			const logger = mockLogger();
+			const logger = new SpyIntegrationLogger();
 			ignoreStringPlugins(['remark-toc', ['rehype-highlight', {}]], logger);
 			// One warning per string plugin + one summary warning
-			assert.equal(logger.warnings.length, 3);
+			assert.equal(logger.messages.filter((m) => m.level === 'warn').length, 3);
 		});
 
 		it('returns empty array for all string plugins', () => {
-			const logger = mockLogger();
+			const logger = new SpyIntegrationLogger();
 			const result = ignoreStringPlugins(['remark-toc'], logger);
 			assert.equal(result.length, 0);
 		});
 
 		it('handles array-based function plugins [function, options]', () => {
 			const fnPlugin = () => {};
-			const logger = mockLogger();
+			const logger = new SpyIntegrationLogger();
 			const result = ignoreStringPlugins([[fnPlugin, { option: true }]], logger);
 			assert.equal(result.length, 1);
-			assert.equal(logger.warnings.length, 0);
+			assert.equal(logger.messages.filter((m) => m.level === 'warn').length, 0);
 		});
 	});
 });