feat(jest-runtime): calling jest.resetModules function will clear FS and transform cache

CHANGELOG.md

@@ -34,6 +34,7 @@
 - `[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-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))
 - `[jest-test-result]` Add duration property to JSON test output ([#12518](https://github.com/facebook/jest/pull/12518))
 - `[jest-worker]` [**BREAKING**] Allow only absolute `workerPath` ([#12343](https://github.com/facebook/jest/pull/12343))

e2e/__tests__/clearFSAndTransformCache.test.ts

@@ -0,0 +1,51 @@
+/**
+ * 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 {tmpdir} from 'os';
+import * as path from 'path';
+import {cleanup, writeFiles} from '../Utils';
+import runJest from '../runJest';
+
+const dir = path.resolve(tmpdir(), 'clear_FS_and_transform_cache');
+const testFileContent = `
+'use strict';
+
+const fs = require('fs');
+const path = require('path');
+
+const absoluteTestHelperFile = path.resolve(__dirname, './testHelper.js');
+
+test('value is 1', () => {
+  const value = require('./testHelper');
+  expect(value).toBe(1);
+});
+
+test('value is 1 after file is changed', () => {
+  fs.writeFileSync(absoluteTestHelperFile, 'module.exports = 2;');
+  const value = require('./testHelper');
+  expect(value).toBe(1);
+});
+
+test('value is 2 after calling "jest.resetModules"', () => {
+  jest.resetModules();
+  const value = require('./testHelper');
+  expect(value).toBe(2);
+});
+`;
+
+beforeEach(() => cleanup(dir));
+afterAll(() => cleanup(dir));
+
+test('clear FS and transform cache', () => {
+  writeFiles(dir, {
+    'package.json': JSON.stringify({jest: {testEnvironment: 'node'}}),
+    'test.js': testFileContent,
+    'testHelper.js': 'module.exports = 1;',
+  });
+  const {exitCode} = runJest(dir);
+  expect(exitCode).toBe(0);
+});

packages/jest-runtime/src/index.ts

@@ -1141,6 +1141,8 @@ export default class Runtime {
     this._esmoduleRegistry.clear();
     this._cjsNamedExports.clear();
     this._moduleMockRegistry.clear();
+    this._cacheFS.clear();
+    this._fileTransforms.clear();
 
     if (this._environment) {
       if (this._environment.global) {