Implement tests for type definitions in Jest

.eslintrc.js

@@ -114,6 +114,14 @@ module.exports = {
         'import/no-extraneous-dependencies': 0,
       },
     },
+    {
+      files: ['test-types/*.test.ts'],
+      rules: {
+        'jest/no-focused-tests': 0,
+        'jest/no-identical-title': 0,
+        'jest/valid-expect': 0,
+      },
+    },
   ],
   parser: 'babel-eslint',
   plugins: ['markdown', 'import', 'prettier', 'eslint-comments'],
@@ -128,6 +136,7 @@ module.exports = {
       2,
       {
         devDependencies: [
+          '/test-types/**',
           '**/__tests__/**',
           '**/__mocks__/**',
           '**/?(*.)(spec|test).js?(x)',

.github/workflows/nodejs.yml

@@ -39,6 +39,8 @@ jobs:
         run: yarn
       - name: build
         run: yarn build
+      - name: test typings
+        run: yarn test-types
       - name: verify TypeScript@3.8 compatibility
         run: yarn verify-old-ts
       - name: run eslint

jest.config.js

@@ -35,6 +35,7 @@ module.exports = {
   ],
   testEnvironment: './packages/jest-environment-node',
   testPathIgnorePatterns: [
+    '/test-types/',
     '/__arbitraries__/',
     '/node_modules/',
     '/examples/',

jest.config.types.js

@@ -0,0 +1,35 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+'use strict';
+
+const assert = require('assert');
+const baseConfig = require('./jest.config');
+
+const {
+  modulePathIgnorePatterns,
+  testPathIgnorePatterns,
+  watchPathIgnorePatterns,
+} = baseConfig;
+
+assert.strictEqual(
+  testPathIgnorePatterns[0],
+  '/test-types/',
+  'First entry must be types',
+);
+
+module.exports = {
+  displayName: {
+    color: 'blue',
+    name: 'types',
+  },
+  modulePathIgnorePatterns,
+  runner: 'jest-runner-tsd',
+  testMatch: ['<rootDir>/test-types/*.test.ts'],
+  testPathIgnorePatterns: testPathIgnorePatterns.slice(1),
+  watchPathIgnorePatterns,
+};

package.json

@@ -55,12 +55,14 @@
     "istanbul-reports": "^3.0.0",
     "jest": "workspace:packages/jest",
     "jest-junit": "^11.0.1",
+    "jest-runner-tsd": "^1.1.0",
     "jest-silent-reporter": "^0.2.1",
     "jest-snapshot-serializer-raw": "^1.1.0",
     "jest-watch-typeahead": "^0.6.0",
     "jquery": "^3.2.1",
     "lerna": "^3.20.2",
     "micromatch": "^4.0.2",
+    "mlh-tsd": "^0.14.1",
     "mock-fs": "^4.4.1",
     "prettier": "^2.0.1",
     "progress": "^2.0.0",
@@ -90,6 +92,7 @@
     "lint:prettier": "prettier '**/*.{md,yml,yaml}' 'website/static/**/*.{css,js}' --write --ignore-path .gitignore",
     "lint:prettier:ci": "prettier '**/*.{md,yml,yaml}' 'website/static/**/*.{css,js}' --check --ignore-path .gitignore",
     "publish": "yarn build-clean && yarn build && lerna publish --silent",
+    "test-types": "yarn jest --config jest.config.types.js",
     "test-ci": "yarn jest-coverage --color -i --config jest.config.ci.js && yarn test-leak && node ./scripts/mapCoverage.js && codecov",
     "test-ci-partial": "yarn jest --color -i --config jest.config.ci.js",
     "test-pretty-format-perf": "node packages/pretty-format/perf/test.js",

test-types/empty.d.ts

@@ -0,0 +1,9 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * This has to be a empty file
+ * @see https://github.com/MLH-Fellowship/jest-runner-tsd/blob/e25720040939fc79ab38d73c1495be90d5b92566/README.md#for-typescript-projects
+ */

test-types/top-level-jest-namespace.test.ts

@@ -0,0 +1,81 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @type ./empty.d.ts
+ */
+
+import {expectError, expectType} from 'mlh-tsd';
+//eslint-disable-next-line import/no-extraneous-dependencies
+import {jest} from '@jest/globals';
+
+expectType<void>(jest.addMatchers({}));
+expectType<typeof jest>(jest.autoMockOff());
+expectType<typeof jest>(jest.autoMockOn());
+expectType<typeof jest>(jest.clearAllMocks());
+expectType<void>(jest.clearAllTimers());
+expectType<typeof jest>(jest.resetAllMocks());
+expectType<typeof jest>(jest.restoreAllMocks());
+expectType<void>(jest.clearAllTimers());
+expectType<typeof jest>(jest.deepUnmock('moduleName'));
+expectType<typeof jest>(jest.disableAutomock());
+expectType<typeof jest>(jest.doMock('moduleName'));
+expectType<typeof jest>(jest.doMock('moduleName', jest.fn()));
+
+expectError(jest.doMock('moduleName', jest.fn(), {}));
+expectError(jest.doMock('moduleName', jest.fn(), {virtual: true}));
+
+expectType<typeof jest>(jest.dontMock('moduleName'));
+expectType<typeof jest>(jest.enableAutomock());
+expectType<typeof jest>(jest.mock('moduleName'));
+expectType<typeof jest>(jest.mock('moduleName', jest.fn()));
+expectType<typeof jest>(jest.mock('moduleName', jest.fn(), {}));
+expectType<typeof jest>(jest.mock('moduleName', jest.fn(), {virtual: true}));
+expectType<typeof jest>(jest.resetModuleRegistry());
+expectType<typeof jest>(jest.resetModules());
+expectType<typeof jest>(jest.isolateModules(() => {}));
+expectType<typeof jest>(jest.retryTimes(3));
+
+expectType<void>(jest.runAllImmediates());
+expectType<void>(jest.runAllTicks());
+expectType<void>(jest.runAllTimers());
+expectType<void>(jest.runOnlyPendingTimers());
+expectType<void>(jest.runTimersToTime(9001));
+expectType<void>(jest.advanceTimersByTime(9001));
+
+expectType<typeof jest>(jest.setMock('moduleName', {}));
+expectType<typeof jest>(jest.setMock('moduleName', {}));
+expectType<typeof jest>(jest.setMock('moduleName', {a: 'b'}));
+expectType<typeof jest>(jest.setTimeout(9001));
+expectType<typeof jest>(jest.unmock('moduleName'));
+expectType<typeof jest>(jest.useFakeTimers());
+expectType<typeof jest>(jest.useRealTimers());
+
+jest.advanceTimersToNextTimer();
+jest.advanceTimersToNextTimer(2);
+
+// https://jestjs.io/docs/en/jest-object#jestusefaketimersimplementation-modern--legacy
+expectType<typeof jest>(jest.useFakeTimers('modern'));
+expectType<typeof jest>(jest.useFakeTimers('legacy'));
+
+expectError(jest.useFakeTimers('foo'));
+
+// https://jestjs.io/docs/en/jest-object#jestsetsystemtimenow-number--date
+expectType<void>(jest.setSystemTime());
+expectType<void>(jest.setSystemTime(0));
+expectType<void>(jest.setSystemTime(new Date(0)));
+
+expectError(jest.setSystemTime('foo'));
+
+// https://jestjs.io/docs/en/jest-object#jestgetrealsystemtime
+expectType<number>(jest.getRealSystemTime());
+
+expectError(jest.getRealSystemTime('foo'));
+
+// https://jestjs.io/docs/en/jest-object#jestrequireactualmodulename
+expectType<unknown>(jest.requireActual('./thisReturnsTheActualModule'));
+
+// https://jestjs.io/docs/en/jest-object#jestrequiremockmodulename
+expectType<unknown>(jest.requireMock('./thisAlwaysReturnsTheMock'));