Implement tests for type definitions in Jest

.eslintrc.js

@@ -114,6 +114,17 @@ module.exports = {
         'import/no-extraneous-dependencies': 0,
       },
     },
+    {
+      files: ['test-types/*.test.ts'],
+      rules: {
+        '@typescript-eslint/array-type': 0,
+        'eslint-comments/disable-enable-pair': 0,
+        'jest/no-focused-tests': 0,
+        'jest/no-identical-title': 0,
+        'jest/valid-expect': 0,
+        'sort-keys': 0,
+      },
+    },
   ],
   parser: 'babel-eslint',
   plugins: ['markdown', 'import', 'prettier', 'eslint-comments'],
@@ -128,6 +139,7 @@ module.exports = {
       2,
       {
         devDependencies: [
+          '/test-types/**',
           '**/__tests__/**',
           '**/__mocks__/**',
           '**/?(*.)(spec|test).js?(x)',

jest.config.js

@@ -27,14 +27,23 @@ module.exports = {
     'website/.*',
     'e2e/runtime-internal-module-registry/__mocks__',
   ],
-  projects: ['<rootDir>', '<rootDir>/examples/*/'],
+  projects: [
+    '<rootDir>',
+    '<rootDir>/examples/*/',
+    {
+      displayName: 'typings test',
+      runner: 'jest-runner-tsd',
+      testMatch: ['<rootDir>/test-types/*.test.ts'],
+    },
+  ],
   setupFilesAfterEnv: ['<rootDir>/testSetupFile.js'],
   snapshotSerializers: [
     '<rootDir>/packages/pretty-format/build/plugins/ConvertAnsi.js',
     require.resolve('jest-snapshot-serializer-raw'),
   ],
   testEnvironment: './packages/jest-environment-node',
   testPathIgnorePatterns: [
+    '/test-types/',
     '/__arbitraries__/',
     '/node_modules/',
     '/examples/',

package.json

@@ -55,12 +55,14 @@
     "istanbul-reports": "^3.0.0",
     "jest": "workspace:packages/jest",
     "jest-junit": "^11.0.1",
+    "jest-runner-tsd": "^1.0.1",
     "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",

test-types/empty.d.ts

@@ -0,0 +1,8 @@
+/**
+ * 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
+ */

test-types/failing.test.ts

@@ -0,0 +1,22 @@
+/**
+ * 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 {expectType} from 'mlh-tsd';
+//eslint-disable-next-line import/no-extraneous-dependencies
+import {jest} from '@jest/globals';
+
+// DEMO: The following three tests should fail
+expectType<string>(jest.addMatchers({}));
+expectType<void>(jest.autoMockOff());
+expectType<void>(jest.autoMockOn());
+
+// DEMO: The following three tests should pass
+expectType<typeof jest>(jest.clearAllMocks());
+expectType<void>(jest.clearAllTimers());
+expectType<typeof jest>(jest.resetAllMocks());

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'));