fix: write snapshots to disk even if FS is mocked

Fixes #5270

e2e/__tests__/__snapshots__/snapshot-mock-fs.test.js.snap

@@ -0,0 +1,9 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`store snapshot even if fs is mocked 1`] = `
+"Test Suites: 1 passed, 1 total
+Tests:       1 passed, 1 total
+Snapshots:   1 written, 1 total
+Time:        <<REPLACED>>
+Ran all test suites."
+`;

e2e/__tests__/snapshot-mock-fs.test.js

@@ -0,0 +1,40 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. 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.
+ *
+ * @flow
+ */
+'use strict';
+
+const rimraf = require('rimraf');
+const path = require('path');
+const {extractSummary} = require('../Utils');
+const runJest = require('../runJest');
+
+const DIR = path.resolve(__dirname, '../snapshot-mock-fs');
+const snapshotDir = path.resolve(DIR, '__tests__/__snapshots__');
+const snapshotFile = path.resolve(snapshotDir, 'snapshot.test.js.snap');
+
+beforeEach(() => rimraf.sync(snapshotDir));
+afterAll(() => rimraf.sync(snapshotDir));
+
+test('store snapshot even if fs is mocked', () => {
+  const {json, status, stderr} = runJest.json(DIR, ['--ci=false']);
+
+  expect(status).toBe(0);
+  expect(json.numTotalTests).toBe(1);
+  expect(json.numPassedTests).toBe(1);
+
+  expect(stderr).toMatch('1 snapshot written from 1 test suite.');
+  expect(extractSummary(stderr).summary).toMatchSnapshot();
+
+  // $FlowFixMe dynamic require
+  const content = require(snapshotFile);
+  expect(content['snapshot 1']).toBe(`
+Object {
+  "foo": "bar",
+}
+`);
+});

e2e/snapshot-mock-fs/__tests__/snapshot.test.js

@@ -0,0 +1,19 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. 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.
+ *
+ * @emails oncall+jsinfra
+ */
+'use strict';
+
+const fs = require('fs');
+
+fs.writeFileSync = jest.fn();
+
+test('snapshot', () => {
+  const thing = {foo: 'bar'};
+
+  expect(thing).toMatchSnapshot();
+});

e2e/snapshot-mock-fs/package.json

@@ -0,0 +1,5 @@
+{
+  "jest": {
+    "testEnvironment": "node"
+  }
+}

packages/jest-snapshot/src/__tests__/utils.test.js

@@ -5,11 +5,15 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-jest.mock('fs');
+jest.mock('../bound_fs', () => ({
+  boundExistsSync: jest.fn(() => true),
+  boundReadFile: jest.fn(),
+  boundWriteFile: jest.fn(),
+}));
 
-const fs = require('fs');
 const path = require('path');
 const chalk = require('chalk');
+const boundFs = require('../bound_fs');
 
 const {
   getSnapshotData,
@@ -23,18 +27,8 @@ const {
   SNAPSHOT_VERSION_WARNING,
 } = require('../utils');
 
-const writeFileSync = fs.writeFileSync;
-const readFileSync = fs.readFileSync;
-const existsSync = fs.existsSync;
 beforeEach(() => {
-  fs.writeFileSync = jest.fn();
-  fs.readFileSync = jest.fn();
-  fs.existsSync = jest.fn(() => true);
-});
-afterEach(() => {
-  fs.writeFileSync = writeFileSync;
-  fs.readFileSync = readFileSync;
-  fs.existsSync = existsSync;
+  jest.clearAllMocks();
 });
 
 test('keyToTestName()', () => {
@@ -57,7 +51,7 @@ test('saveSnapshotFile() works with \r\n', () => {
   };
 
   saveSnapshotFile(data, filename);
-  expect(fs.writeFileSync).toBeCalledWith(
+  expect(boundFs.boundWriteFile).toBeCalledWith(
     filename,
     `// Jest Snapshot v1, ${SNAPSHOT_GUIDE_LINK}\n\n` +
       'exports[`myKey`] = `<div>\n</div>`;\n',
@@ -71,7 +65,7 @@ test('saveSnapshotFile() works with \r', () => {
   };
 
   saveSnapshotFile(data, filename);
-  expect(fs.writeFileSync).toBeCalledWith(
+  expect(boundFs.boundWriteFile).toBeCalledWith(
     filename,
     `// Jest Snapshot v1, ${SNAPSHOT_GUIDE_LINK}\n\n` +
       'exports[`myKey`] = `<div>\n</div>`;\n',
@@ -80,7 +74,9 @@ test('saveSnapshotFile() works with \r', () => {
 
 test('getSnapshotData() throws when no snapshot version', () => {
   const filename = path.join(__dirname, 'old-snapshot.snap');
-  fs.readFileSync = jest.fn(() => 'exports[`myKey`] = `<div>\n</div>`;\n');
+  boundFs.boundReadFile.mockImplementation(
+    () => 'exports[`myKey`] = `<div>\n</div>`;\n',
+  );
   const update = 'none';
 
   expect(() => getSnapshotData(filename, update)).toThrowError(
@@ -95,7 +91,7 @@ test('getSnapshotData() throws when no snapshot version', () => {
 
 test('getSnapshotData() throws for older snapshot version', () => {
   const filename = path.join(__dirname, 'old-snapshot.snap');
-  fs.readFileSync = jest.fn(
+  boundFs.boundReadFile.mockImplementation(
     () =>
       `// Jest Snapshot v0.99, ${SNAPSHOT_GUIDE_LINK}\n\n` +
       'exports[`myKey`] = `<div>\n</div>`;\n',
@@ -118,7 +114,7 @@ test('getSnapshotData() throws for older snapshot version', () => {
 
 test('getSnapshotData() throws for newer snapshot version', () => {
   const filename = path.join(__dirname, 'old-snapshot.snap');
-  fs.readFileSync = jest.fn(
+  boundFs.boundReadFile.mockImplementation(
     () =>
       `// Jest Snapshot v2, ${SNAPSHOT_GUIDE_LINK}\n\n` +
       'exports[`myKey`] = `<div>\n</div>`;\n',
@@ -141,23 +137,27 @@ test('getSnapshotData() throws for newer snapshot version', () => {
 
 test('getSnapshotData() does not throw for when updating', () => {
   const filename = path.join(__dirname, 'old-snapshot.snap');
-  fs.readFileSync = jest.fn(() => 'exports[`myKey`] = `<div>\n</div>`;\n');
+  boundFs.boundReadFile.mockImplementation(
+    () => 'exports[`myKey`] = `<div>\n</div>`;\n',
+  );
   const update = 'all';
 
   expect(() => getSnapshotData(filename, update)).not.toThrow();
 });
 
 test('getSnapshotData() marks invalid snapshot dirty when updating', () => {
   const filename = path.join(__dirname, 'old-snapshot.snap');
-  fs.readFileSync = jest.fn(() => 'exports[`myKey`] = `<div>\n</div>`;\n');
+  boundFs.boundReadFile.mockImplementation(
+    () => 'exports[`myKey`] = `<div>\n</div>`;\n',
+  );
   const update = 'all';
 
   expect(getSnapshotData(filename, update)).toMatchObject({dirty: true});
 });
 
 test('getSnapshotData() marks valid snapshot not dirty when updating', () => {
   const filename = path.join(__dirname, 'old-snapshot.snap');
-  fs.readFileSync = jest.fn(
+  boundFs.boundReadFile.mockImplementation(
     () =>
       `// Jest Snapshot v${SNAPSHOT_VERSION}, ${SNAPSHOT_GUIDE_LINK}\n\n` +
       'exports[`myKey`] = `<div>\n</div>`;\n',
@@ -171,7 +171,7 @@ test('escaping', () => {
   const filename = path.join(__dirname, 'escaping.snap');
   const data = '"\'\\';
   saveSnapshotFile({key: data}, filename);
-  const writtenData = fs.writeFileSync.mock.calls[0][1];
+  const writtenData = boundFs.boundWriteFile.mock.calls[0][1];
   expect(writtenData).toBe(
     `// Jest Snapshot v1, ${SNAPSHOT_GUIDE_LINK}\n\n` +
       'exports[`key`] = `"\'\\\\`;\n',

packages/jest-snapshot/src/bound_fs.js

@@ -0,0 +1,16 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. 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.
+ *
+ * @flow
+ */
+
+// This file exists so that mocks in userland does not affect snapshots
+
+import fs from 'fs';
+
+export const boundReadFile = fs.readFileSync.bind(fs);
+export const boundWriteFile = fs.writeFileSync.bind(fs);
+export const boundExistsSync = fs.existsSync.bind(fs);

packages/jest-snapshot/src/utils.js

@@ -11,12 +11,13 @@ import type {Path, SnapshotUpdateState} from 'types/Config';
 
 import {getSerializers} from './plugins';
 import chalk from 'chalk';
-import fs from 'fs';
 import mkdirp from 'mkdirp';
 import naturalCompare from 'natural-compare';
 import path from 'path';
 import prettyFormat from 'pretty-format';
 
+import {boundReadFile, boundWriteFile, boundExistsSync} from './bound_fs';
+
 export const SNAPSHOT_VERSION = '1';
 const SNAPSHOT_VERSION_REGEXP = /^\/\/ Jest Snapshot v(.+),/;
 export const SNAPSHOT_GUIDE_LINK = 'https://goo.gl/fbAQLP';
@@ -99,9 +100,9 @@ export const getSnapshotData = (
   let snapshotContents = '';
   let dirty = false;
 
-  if (fs.existsSync(snapshotPath)) {
+  if (boundExistsSync(snapshotPath)) {
     try {
-      snapshotContents = fs.readFileSync(snapshotPath, 'utf8');
+      snapshotContents = boundReadFile(snapshotPath, 'utf8');
       // eslint-disable-next-line no-new-func
       const populate = new Function('exports', snapshotContents);
       // $FlowFixMe
@@ -172,7 +173,7 @@ export const saveSnapshotFile = (
     );
 
   ensureDirectoryExists(snapshotPath);
-  fs.writeFileSync(
+  boundWriteFile(
     snapshotPath,
     writeSnapshotVersion() + '\n\n' + snapshots.join('\n\n') + '\n',
   );