Enable rule for TypeScript test files only

Author: Mrtenz

packages/jest/src/__test__/dummy.test.ts

@@ -0,0 +1,2 @@
+// This file is only used to test the config.
+console.log('Hello, world!');

packages/jest/src/index.mjs

@@ -5,44 +5,54 @@ import globals from 'globals';
 /**
  * @type {import('eslint').Linter.Config[]}
  */
-const config = createConfig({
-  name: '@metamask/eslint-config-jest',
+const config = createConfig([
+  {
+    name: '@metamask/eslint-config-jest',
 
-  extends: [jest.configs['flat/recommended'], jest.configs['flat/style']],
+    extends: [jest.configs['flat/recommended'], jest.configs['flat/style']],
 
-  languageOptions: {
-    globals: {
-      ...globals.jest,
+    languageOptions: {
+      globals: {
+        ...globals.jest,
+      },
+    },
+
+    rules: {
+      'jest/consistent-test-it': ['error', { fn: 'it' }],
+      'jest/no-duplicate-hooks': 'error',
+      'jest/no-conditional-in-test': 'error',
+      'jest/no-test-return-statement': 'error',
+      'jest/prefer-hooks-on-top': 'error',
+      'jest/prefer-lowercase-title': ['error', { ignore: ['describe'] }],
+      'jest/prefer-spy-on': 'error',
+      'jest/prefer-strict-equal': 'error',
+      'jest/prefer-todo': 'error',
+      'jest/require-top-level-describe': 'error',
+      'jest/require-to-throw-message': 'error',
+      'jest/valid-expect': ['error', { alwaysAwait: true }],
+      'jest/no-restricted-matchers': [
+        'error',
+        {
+          resolves: 'Use `expect(await promise)` instead.',
+          toBeFalsy: 'Avoid `toBeFalsy`',
+          toBeTruthy: 'Avoid `toBeTruthy`',
+          toMatchSnapshot: 'Use `toMatchInlineSnapshot()` instead',
+          toThrowErrorMatchingSnapshot:
+            'Use `toThrowErrorMatchingInlineSnapshot()` instead',
+        },
+      ],
     },
   },
+  {
+    name: '@metamask/eslint-config-jest/typescript',
 
-  rules: {
-    '@typescript-eslint/unbound-method': 'off',
-    'jest/consistent-test-it': ['error', { fn: 'it' }],
-    'jest/no-duplicate-hooks': 'error',
-    'jest/no-conditional-in-test': 'error',
-    'jest/no-test-return-statement': 'error',
-    'jest/prefer-hooks-on-top': 'error',
-    'jest/prefer-lowercase-title': ['error', { ignore: ['describe'] }],
-    'jest/prefer-spy-on': 'error',
-    'jest/prefer-strict-equal': 'error',
-    'jest/prefer-todo': 'error',
-    'jest/require-top-level-describe': 'error',
-    'jest/require-to-throw-message': 'error',
-    'jest/unbound-method': 'error',
-    'jest/valid-expect': ['error', { alwaysAwait: true }],
-    'jest/no-restricted-matchers': [
-      'error',
-      {
-        resolves: 'Use `expect(await promise)` instead.',
-        toBeFalsy: 'Avoid `toBeFalsy`',
-        toBeTruthy: 'Avoid `toBeTruthy`',
-        toMatchSnapshot: 'Use `toMatchInlineSnapshot()` instead',
-        toThrowErrorMatchingSnapshot:
-          'Use `toThrowErrorMatchingInlineSnapshot()` instead',
-      },
-    ],
+    files: ['**/*.test.ts', '**/*.test.tsx', '**/*.test.mts', '**/*.test.cts'],
+
+    rules: {
+      '@typescript-eslint/unbound-method': 'off',
+      'jest/unbound-method': 'error',
+    },
   },
-});
+]);
 
 export default config;

packages/jest/src/index.test.mjs

@@ -1,4 +1,6 @@
 import { ESLint } from 'eslint';
+import globals from 'globals';
+import { resolve } from 'path';
 import { describe, it, expect } from 'vitest';
 
 import config from './index.mjs';
@@ -15,4 +17,32 @@ describe('index', () => {
     expect(result[0].warningCount).toBe(0);
     expect(result[0].errorCount).toBe(0);
   });
+
+  it('is a valid ESLint config for TypeScript files', async () => {
+    const api = new ESLint({
+      baseConfig: config,
+      overrideConfig: {
+        languageOptions: {
+          globals: {
+            ...globals.node,
+          },
+          parserOptions: {
+            tsconfigRootDir: resolve(import.meta.dirname, '..'),
+            project: 'tsconfig.json',
+          },
+        },
+      },
+    });
+
+    // In order to test rules that require type information, we need to actually
+    // compile the file with TypeScript, so rather than using `api.lintText()`,
+    // we use `api.lintFiles()` and pass in a file that we know will pass.
+    const result = await api.lintFiles(
+      resolve(import.meta.dirname, '__test__/dummy.test.ts'),
+    );
+
+    expect(result[0].messages).toStrictEqual([]);
+    expect(result[0].warningCount).toBe(0);
+    expect(result[0].errorCount).toBe(0);
+  });
 });

packages/jest/tsconfig.json

@@ -0,0 +1,6 @@
+{
+  "compilerOptions": {
+    "strictNullChecks": true
+  },
+  "include": ["src"]
+}