feat(jest-runner): improve typings by exposing TestRunner abstract classes

CHANGELOG.md

@@ -42,6 +42,7 @@
 - `[jest-resolve, jest-runtime]` Add support for async resolver ([#11540](https://github.com/facebook/jest/pull/11540))
 - `[jest-runner]` Allow `setupFiles` module to export an async function ([#12042](https://github.com/facebook/jest/pull/12042))
 - `[jest-runner]` Allow passing `testEnvironmentOptions` via docblocks ([#12470](https://github.com/facebook/jest/pull/12470))
+- `[jest-runner]` Exposing `CallbackTestRunner`, `EmittingTestRunner` abstract classes to help typing third party runners ([#12646](https://github.com/facebook/jest/pull/12646))
 - `[jest-runtime]` [**BREAKING**] `Runtime.createHasteMap` now returns a promise ([#12008](https://github.com/facebook/jest/pull/12008))
 - `[jest-runtime]` Calling `jest.resetModules` function will clear FS and transform cache ([#12531](https://github.com/facebook/jest/pull/12531))
 - `[@jest/schemas]` New module for JSON schemas for Jest's config ([#12384](https://github.com/facebook/jest/pull/12384))

packages/jest-core/src/TestScheduler.ts

@@ -29,7 +29,7 @@ import {
 import {createScriptTransformer} from '@jest/transform';
 import type {Config} from '@jest/types';
 import {formatExecError} from 'jest-message-util';
-import type TestRunner from 'jest-runner';
+import type {JestTestRunner, TestRunnerContext} from 'jest-runner';
 import type {Context} from 'jest-runtime';
 import {
   buildSnapshotResolver,
@@ -40,6 +40,11 @@ import ReporterDispatcher from './ReporterDispatcher';
 import type TestWatcher from './TestWatcher';
 import {shouldRunInBand} from './testSchedulerHelper';
 
+type TestRunnerConstructor = new (
+  globalConfig: Config.GlobalConfig,
+  context: TestRunnerContext,
+) => JestTestRunner;
+
 export type TestSchedulerOptions = {
   startRun: (globalConfig: Config.GlobalConfig) => void;
 };
@@ -206,14 +211,14 @@ class TestScheduler {
       showStatus: !runInBand,
     });
 
-    const testRunners: {[key: string]: TestRunner} = Object.create(null);
-    const contextsByTestRunner = new WeakMap<TestRunner, Context>();
+    const testRunners: Record<string, JestTestRunner> = Object.create(null);
+    const contextsByTestRunner = new WeakMap<JestTestRunner, Context>();
     await Promise.all(
       Array.from(contexts).map(async context => {
         const {config} = context;
         if (!testRunners[config.runner]) {
           const transformer = await createScriptTransformer(config);
-          const Runner: typeof TestRunner =
+          const Runner: TestRunnerConstructor =
             await transformer.requireAndTranspileModule(config.runner);
           const runner = new Runner(this._globalConfig, {
             changedFiles: this._context.changedFiles,
@@ -262,14 +267,7 @@ class TestScheduler {
               ),
             ];
 
-            await testRunner.runTests(
-              tests,
-              watcher,
-              undefined,
-              undefined,
-              undefined,
-              testRunnerOptions,
-            );
+            await testRunner.runTests(tests, watcher, testRunnerOptions);
 
             unsubscribes.forEach(sub => sub());
           } else {
@@ -310,7 +308,7 @@ class TestScheduler {
   }
 
   private _partitionTests(
-    testRunners: Record<string, TestRunner>,
+    testRunners: Record<string, JestTestRunner>,
     tests: Array<Test>,
   ): Record<string, Array<Test>> | null {
     if (Object.keys(testRunners).length > 1) {

packages/jest-runner/__typetests__/jest-runner.test.ts

@@ -0,0 +1,73 @@
+/**
+ * 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.
+ */
+
+import {expectType} from 'tsd-lite';
+import type {Test, TestEvents} from '@jest/test-result';
+import type {Config} from '@jest/types';
+import {CallbackTestRunner, EmittingTestRunner} from 'jest-runner';
+import type {
+  OnTestFailure,
+  OnTestStart,
+  OnTestSuccess,
+  TestRunnerContext,
+  TestRunnerOptions,
+  TestWatcher,
+  UnsubscribeFn,
+} from 'jest-runner';
+
+const globalConfig = {} as Config.GlobalConfig;
+const runnerContext = {} as TestRunnerContext;
+
+// CallbackRunner
+
+class CallbackRunner extends CallbackTestRunner {
+  async runTests(
+    tests: Array<Test>,
+    watcher: TestWatcher,
+    onStart: OnTestStart,
+    onResult: OnTestSuccess,
+    onFailure: OnTestFailure,
+    options: TestRunnerOptions,
+  ): Promise<void> {
+    expectType<Config.GlobalConfig>(this._globalConfig);
+    expectType<TestRunnerContext>(this._context);
+
+    return;
+  }
+}
+
+const callbackRunner = new CallbackRunner(globalConfig, runnerContext);
+
+expectType<boolean | undefined>(callbackRunner.isSerial);
+expectType<false>(callbackRunner.supportsEventEmitters);
+
+// EmittingRunner
+
+class EmittingRunner extends EmittingTestRunner {
+  async runTests(
+    tests: Array<Test>,
+    watcher: TestWatcher,
+    options: TestRunnerOptions,
+  ): Promise<void> {
+    expectType<Config.GlobalConfig>(this._globalConfig);
+    expectType<TestRunnerContext>(this._context);
+
+    return;
+  }
+
+  on<Name extends keyof TestEvents>(
+    eventName: string,
+    listener: (eventData: TestEvents[Name]) => void | Promise<void>,
+  ): UnsubscribeFn {
+    return () => {};
+  }
+}
+
+const emittingRunner = new EmittingRunner(globalConfig, runnerContext);
+
+expectType<boolean | undefined>(emittingRunner.isSerial);
+expectType<true>(emittingRunner.supportsEventEmitters);

packages/jest-runner/__typetests__/tsconfig.json

@@ -0,0 +1,11 @@
+{
+  "extends": "../../../tsconfig.json",
+  "compilerOptions": {
+    "noUnusedLocals": false,
+    "noUnusedParameters": false,
+    "skipLibCheck": true,
+
+    "types": []
+  },
+  "include": ["./**/*"]
+}

packages/jest-runner/package.json

@@ -39,10 +39,12 @@
     "throat": "^6.0.1"
   },
   "devDependencies": {
+    "@tsd/typescript": "~4.6.2",
     "@types/exit": "^0.1.30",
     "@types/graceful-fs": "^4.1.2",
     "@types/source-map-support": "^0.5.0",
-    "jest-jasmine2": "^28.0.0-alpha.8"
+    "jest-jasmine2": "^28.0.0-alpha.8",
+    "tsd-lite": "^0.5.1"
   },
   "engines": {
     "node": "^12.13.0 || ^14.15.0 || ^16.13.0 || >=17.0.0"

packages/jest-runner/src/__tests__/testRunner.test.ts

@@ -7,6 +7,7 @@
  */
 
 import {TestWatcher} from '@jest/core';
+import type {TestContext} from '@jest/test-result';
 import {makeGlobalConfig, makeProjectConfig} from '@jest/test-utils';
 import TestRunner from '../index';
 
@@ -29,56 +30,46 @@ jest.mock('../testWorker', () => {});
 test('injects the serializable module map into each worker in watch mode', async () => {
   const globalConfig = makeGlobalConfig({maxWorkers: 2, watch: true});
   const config = makeProjectConfig({rootDir: '/path/'});
-  const serializableModuleMap = jest.fn();
   const runContext = {};
-  const context = {
+  const mockTestContext = {
     config,
-    moduleMap: {toJSON: () => serializableModuleMap},
-  };
+    moduleMap: {toJSON: jest.fn()},
+  } as unknown as TestContext;
 
-  await new TestRunner(globalConfig, {}).runTests(
+  await new TestRunner(globalConfig, runContext).runTests(
     [
-      {context, path: './file.test.js'},
-      {context, path: './file2.test.js'},
+      {context: mockTestContext, path: './file.test.js'},
+      {context: mockTestContext, path: './file2.test.js'},
     ],
     new TestWatcher({isWatchMode: globalConfig.watch}),
-    undefined,
-    undefined,
-    undefined,
     {serial: false},
   );
 
-  expect(mockWorkerFarm.worker.mock.calls).toEqual([
-    [
-      {
-        config,
-        context: runContext,
-        globalConfig,
-        path: './file.test.js',
-      },
-    ],
-    [
-      {
-        config,
-        context: runContext,
-        globalConfig,
-        path: './file2.test.js',
-      },
-    ],
-  ]);
+  expect(mockWorkerFarm.worker).toBeCalledTimes(2);
+
+  expect(mockWorkerFarm.worker).nthCalledWith(1, {
+    config,
+    context: runContext,
+    globalConfig,
+    path: './file.test.js',
+  });
+
+  expect(mockWorkerFarm.worker).nthCalledWith(2, {
+    config,
+    context: runContext,
+    globalConfig,
+    path: './file2.test.js',
+  });
 });
 
 test('assign process.env.JEST_WORKER_ID = 1 when in runInBand mode', async () => {
   const globalConfig = makeGlobalConfig({maxWorkers: 1, watch: false});
   const config = makeProjectConfig({rootDir: '/path/'});
-  const context = {config};
+  const context = {config} as TestContext;
 
   await new TestRunner(globalConfig, {}).runTests(
     [{context, path: './file.test.js'}],
     new TestWatcher({isWatchMode: globalConfig.watch}),
-    undefined,
-    undefined,
-    undefined,
     {serial: true},
   );