Support jest.config.mts

manthansubhash01 · manthansubhash01 · commit 919e4de63f74 · 2026-03-24T22:54:50.000+05:30
diff --git a/docs/Configuration.md b/docs/Configuration.md
@@ -5,7 +5,7 @@ title: Configuring Jest
 
 The Jest philosophy is to work great by default, but sometimes you just need more configuration power.
 
-It is recommended to define the configuration in a dedicated JavaScript, TypeScript or JSON file. The file will be discovered automatically, if it is named `jest.config.js|ts|mjs|cjs|cts|json`. You can use [`--config`](CLI.md#--configpath) flag to pass an explicit path to the file.
+It is recommended to define the configuration in a dedicated JavaScript, TypeScript or JSON file. The file will be discovered automatically, if it is named `jest.config.js|ts|mts|mjs|cjs|cts|json`. You can use [`--config`](CLI.md#--configpath) flag to pass an explicit path to the file.
 
 :::note
 
diff --git a/e2e/__tests__/readInitialOptions.test.ts b/e2e/__tests__/readInitialOptions.test.ts
@@ -53,6 +53,7 @@ describe('readInitialOptions', () => {
     ['pkg-config', 'package.json', 'package.json'],
     ['ts-node-config', 'jest.config.ts', 'jest.config.ts'],
     ['ts-esbuild-register-config', 'jest.config.ts', 'jest.config.ts'],
+    ['mts-config', 'jest.config.mts', 'jest.config.mts'],
     ['mjs-config', 'jest.config.mjs', 'jest.config.mjs'],
     ['json-config', 'jest.config.json', 'jest.config.json'],
     ['async-config', 'jest.config.js', 'async-config'],
diff --git a/e2e/__tests__/tsIntegration.test.ts b/e2e/__tests__/tsIntegration.test.ts
@@ -97,6 +97,42 @@ describe('when `Config` type is imported from "@jest/types"', () => {
     expect(globalConfig.verbose).toBe(true);
   });
 
+  test('with object config exported from MTS file when package.json#type=commonjs', () => {
+    writeFiles(DIR, {
+      '__tests__/dummy.test.js': "test('dummy', () => expect(123).toBe(123));",
+      'jest.config.mts': `
+        import type {Config} from '@jest/types';
+        const config: Config.InitialOptions = {displayName: 'ts-mts-object-config', verbose: true};
+        export default config;
+      `,
+      'package.json': '{"type": "commonjs"}',
+    });
+
+    const {configs, globalConfig} = getConfig(path.join(DIR));
+
+    expect(configs).toHaveLength(1);
+    expect(configs[0].displayName?.name).toBe('ts-mts-object-config');
+    expect(globalConfig.verbose).toBe(true);
+  });
+
+  test('with object config exported from MTS file when package.json#type=module', () => {
+    writeFiles(DIR, {
+      '__tests__/dummy.test.js': "test('dummy', () => expect(12).toBe(12));",
+      'jest.config.mts': `
+        import type {Config} from '@jest/types';
+        const config: Config.InitialOptions = {displayName: 'ts-mts-esm-object-config', verbose: true};
+        export default config;
+      `,
+      'package.json': '{"type": "module"}',
+    });
+
+    const {configs, globalConfig} = getConfig(path.join(DIR));
+
+    expect(configs).toHaveLength(1);
+    expect(configs[0].displayName?.name).toBe('ts-mts-esm-object-config');
+    expect(globalConfig.verbose).toBe(true);
+  });
+
   testIfTsLoader('throws if type errors are encountered', () => {
     writeFiles(DIR, {
       '__tests__/dummy.test.js': "test('dummy', () => expect(123).toBe(123));",
diff --git a/e2e/read-initial-options/mts-config/jest.config.mts b/e2e/read-initial-options/mts-config/jest.config.mts
@@ -0,0 +1,9 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+export default {
+  jestConfig: 'jest.config.mts',
+};
diff --git a/packages/create-jest/src/__tests__/__fixtures__/has-jest-config-file-mts/jest.config.mts b/packages/create-jest/src/__tests__/__fixtures__/has-jest-config-file-mts/jest.config.mts
@@ -0,0 +1,8 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+export default {};
diff --git a/packages/create-jest/src/__tests__/__fixtures__/has-jest-config-file-mts/package.json b/packages/create-jest/src/__tests__/__fixtures__/has-jest-config-file-mts/package.json
@@ -0,0 +1 @@
+{}
diff --git a/packages/create-jest/src/__tests__/__snapshots__/init.test.ts.snap b/packages/create-jest/src/__tests__/__snapshots__/init.test.ts.snap
@@ -54,6 +54,15 @@ Object {
 }
 `;
 
+exports[`init has-jest-config-file-mts ask the user whether to override config or not user answered with "Yes" 1`] = `
+Object {
+  "initial": true,
+  "message": "It seems that you already have a jest configuration, do you want to override it?",
+  "name": "continue",
+  "type": "confirm",
+}
+`;
+
 exports[`init has-jest-config-file-ts ask the user whether to override config or not user answered with "Yes" 1`] = `
 Object {
   "initial": true,
diff --git a/packages/jest-cli/src/__tests__/args.test.ts b/packages/jest-cli/src/__tests__/args.test.ts
@@ -89,13 +89,13 @@ describe('check', () => {
 
   it('raises an exception if config is not a valid JSON string', () => {
     expect(() => check(argv({config: 'x:1'}))).toThrow(
-      'The --config option requires a JSON string literal, or a file path with one of these extensions: .js, .ts, .mjs, .cjs, .cts, .json',
+      'The --config option requires a JSON string literal, or a file path with one of these extensions: .js, .ts, .mts, .mjs, .cjs, .cts, .json',
     );
   });
 
   it('raises an exception if config is not a supported file type', () => {
     const message =
-      'The --config option requires a JSON string literal, or a file path with one of these extensions: .js, .ts, .mjs, .cjs, .cts, .json';
+      'The --config option requires a JSON string literal, or a file path with one of these extensions: .js, .ts, .mts, .mjs, .cjs, .cts, .json';
 
     expect(() => check(argv({config: 'jest.configjs'}))).toThrow(message);
     expect(() => check(argv({config: 'jest.config.exe'}))).toThrow(message);
diff --git a/packages/jest-config/src/__tests__/readConfigFileAndSetRootDir.test.ts b/packages/jest-config/src/__tests__/readConfigFileAndSetRootDir.test.ts
@@ -14,6 +14,19 @@ import {onNodeVersions} from '@jest/test-utils';
 jest.mock('graceful-fs').mock('jest-util');
 
 describe('readConfigFileAndSetRootDir', () => {
+  describe('TypeScript ESM file', () => {
+    test('reads .mts config and sets `rootDir`', async () => {
+      jest.mocked(requireOrImportModule).mockResolvedValueOnce({notify: true});
+
+      const rootDir = path.resolve('some', 'path', 'to');
+      const config = await readConfigFileAndSetRootDir(
+        path.join(rootDir, 'jest.config.mts'),
+      );
+
+      expect(config).toEqual({notify: true, rootDir});
+    });
+  });
+
   describe('JavaScript file', () => {
     test('reads config and sets `rootDir`', async () => {
       jest.mocked(requireOrImportModule).mockResolvedValueOnce({notify: true});
diff --git a/packages/jest-config/src/constants.ts b/packages/jest-config/src/constants.ts
@@ -15,11 +15,13 @@ export const JEST_CONFIG_EXT_CJS = '.cjs';
 export const JEST_CONFIG_EXT_MJS = '.mjs';
 export const JEST_CONFIG_EXT_JS = '.js';
 export const JEST_CONFIG_EXT_TS = '.ts';
+export const JEST_CONFIG_EXT_MTS = '.mts';
 export const JEST_CONFIG_EXT_CTS = '.cts';
 export const JEST_CONFIG_EXT_JSON = '.json';
 export const JEST_CONFIG_EXT_ORDER = Object.freeze([
   JEST_CONFIG_EXT_JS,
   JEST_CONFIG_EXT_TS,
+  JEST_CONFIG_EXT_MTS,
   JEST_CONFIG_EXT_MJS,
   JEST_CONFIG_EXT_CJS,
   JEST_CONFIG_EXT_CTS,
diff --git a/packages/jest-config/src/readConfigFileAndSetRootDir.ts b/packages/jest-config/src/readConfigFileAndSetRootDir.ts
@@ -16,6 +16,7 @@ import {interopRequireDefault, requireOrImportModule} from 'jest-util';
 import {
   JEST_CONFIG_EXT_CTS,
   JEST_CONFIG_EXT_JSON,
+  JEST_CONFIG_EXT_MTS,
   JEST_CONFIG_EXT_TS,
   PACKAGE_JSON,
 } from './constants';
@@ -26,27 +27,31 @@ interface TsLoader {
 type TsLoaderModule = 'ts-node' | 'esbuild-register';
 // Read the configuration and set its `rootDir`
 // 1. If it's a `package.json` file, we look into its "jest" property
-// 2. If it's a `jest.config.ts` file, we use `ts-node` to transpile & require it
+// 2. If it's a `jest.config.ts`/`jest.config.cts`/`jest.config.mts` file,
+//    we use native TypeScript support when possible, otherwise a TS loader.
 // 3. For any other file, we just require it. If we receive an 'ERR_REQUIRE_ESM'
 //    from node, perform a dynamic import instead.
 export default async function readConfigFileAndSetRootDir(
   configPath: string,
 ): Promise<Config.InitialOptions> {
   const isTS =
     configPath.endsWith(JEST_CONFIG_EXT_TS) ||
+    configPath.endsWith(JEST_CONFIG_EXT_MTS) ||
     configPath.endsWith(JEST_CONFIG_EXT_CTS);
+  const isMTS = configPath.endsWith(JEST_CONFIG_EXT_MTS);
   const isJSON = configPath.endsWith(JEST_CONFIG_EXT_JSON);
   let configObject;
 
   try {
     if (isTS) {
+      // .mts is always ESM, so attempt import-based loading first.
       // @ts-expect-error: Type assertion can be removed once @types/node is updated to 23 https://nodejs.org/api/process.html#processfeaturestypescript
-      if (process.features.typescript) {
+      if (isMTS || process.features.typescript) {
         try {
           // Try native node TypeScript support first.
           configObject = await requireOrImportModule<any>(configPath);
         } catch (requireOrImportModuleError) {
-          if (!(requireOrImportModuleError instanceof SyntaxError)) {
+          if (!(requireOrImportModuleError instanceof SyntaxError) && !isMTS) {
             if (!hasTsLoaderExplicitlyConfigured(configPath)) {
               throw requireOrImportModuleError;
             }
diff --git a/packages/jest-util/src/requireOrImportModule.ts b/packages/jest-util/src/requireOrImportModule.ts
@@ -52,7 +52,7 @@ export default async function requireOrImportModule<T>(
     );
   }
   try {
-    if (filePath.endsWith('.mjs')) {
+    if (filePath.endsWith('.mjs') || filePath.endsWith('.mts')) {
       return importModule(filePath, applyInteropRequireDefault);
     }
 
diff --git a/website/versioned_docs/version-30.0/Configuration.md b/website/versioned_docs/version-30.0/Configuration.md
@@ -5,7 +5,7 @@ title: Configuring Jest
 
 The Jest philosophy is to work great by default, but sometimes you just need more configuration power.
 
-It is recommended to define the configuration in a dedicated JavaScript, TypeScript or JSON file. The file will be discovered automatically, if it is named `jest.config.js|ts|mjs|cjs|cts|json`. You can use [`--config`](CLI.md#--configpath) flag to pass an explicit path to the file.
+It is recommended to define the configuration in a dedicated JavaScript, TypeScript or JSON file. The file will be discovered automatically, if it is named `jest.config.js|ts|mts|mjs|cjs|cts|json`. You can use [`--config`](CLI.md#--configpath) flag to pass an explicit path to the file.
 
 :::note
 
