Allow setting a test environment per file

Fixes #2587

docs/Configuration.md

@@ -352,7 +352,18 @@ To make a dependency explicit instead of implicit, you can call [`expect.addSnap
 ### `testEnvironment` [string]
 Default: `"jsdom"`
 
-The test environment that will be used for testing. The default environment in Jest is a browser-like environment through [jsdom](https://github.com/tmpvar/jsdom). If you are building a node service, you can use the `node` option to use a node-like environment instead. Combining the test environments is currently not possible but the `jsdom` environment can be seen as a superset of the `node` one.
+The test environment that will be used for testing. The default environment in Jest is a browser-like environment through [jsdom](https://github.com/tmpvar/jsdom). If you are building a node service, you can use the `node` option to use a node-like environment instead. If some tests require another environment, you can add a `@jest-environment` docblock.
+
+```js
+/**
+ * @jest-environment jsdom
+ */
+
+test('use jsdom in this test file', () => {
+  const element = document.createElement('div');
+  expect(element).not.toBeNull();
+});
+```
 
 You can create your own module that will be used for setting up the test environment. The module must export a class with `runScript` and `dispose` methods. See the [node](https://github.com/facebook/jest/blob/master/packages/jest-environment-node/src/index.js) or [jsdom](https://github.com/facebook/jest/blob/master/packages/jest-environment-jsdom/src/index.js) environments as examples.
 

integration_tests/__tests__/test-environment-test.js

@@ -0,0 +1,26 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @emails oncall+jsinfra
+ */
+'use strict';
+
+const runJest = require('../runJest');
+const skipOnWindows = require('skipOnWindows');
+
+skipOnWindows.suite();
+
+const testFixturePackage = require('../test-environment/package.json');
+
+it('respects testEnvironment docblock', () => {
+  expect(testFixturePackage.jest.testEnvironment).toEqual('node');
+
+  const result = runJest.json('test-environment').json;
+
+  expect(result.success).toBe(true);
+  expect(result.numTotalTests).toBe(1);
+});

integration_tests/test-environment/__tests__/env-test.js

@@ -0,0 +1,16 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @jest-environment jsdom
+ */
+'use strict';
+/* eslint-env browser*/
+
+test('stub', () => {
+  const element = document.createElement('div');
+  expect(element).not.toBeNull();
+});

integration_tests/test-environment/package.json

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

packages/jest-cli/package.json

@@ -15,6 +15,7 @@
     "istanbul-lib-source-maps": "^1.1.0",
     "jest-changed-files": "^19.0.2",
     "jest-config": "^19.0.2",
+    "jest-docblock": "^19.0.2",
     "jest-environment-jsdom": "^19.0.2",
     "jest-haste-map": "^19.0.0",
     "jest-jasmine2": "^19.0.2",

packages/jest-cli/src/runTest.js

@@ -19,11 +19,35 @@ const {
   NullConsole,
   setGlobal,
 } = require('jest-util');
+
+const {getTestEnvironment} = require('jest-config');
+const fs = require('fs');
+const docblock = require('jest-docblock');
 const getConsoleOutput = require('./reporters/getConsoleOutput');
 
 function runTest(path: Path, config: Config, resolver: Resolver) {
+  let testSource;
+
+  try {
+    testSource = fs.readFileSync(path, 'utf8');
+  } catch (e) {
+    return Promise.reject(e);
+  }
+
+  const parsedDocblock = docblock.parse(docblock.extract(testSource));
+  const customEnvironment = parsedDocblock['jest-environment'];
+  let testEnvironment = config.testEnvironment;
+
+  if (customEnvironment) {
+    testEnvironment = getTestEnvironment(
+      Object.assign({}, config, {
+        testEnvironment: customEnvironment,
+      })
+    );
+  }
+
   /* $FlowFixMe */
-  const TestEnvironment = require(config.testEnvironment);
+  const TestEnvironment = require(testEnvironment);
   /* $FlowFixMe */
   const TestRunner = require(config.testRunner);
   /* $FlowFixMe */
@@ -39,7 +63,7 @@ function runTest(path: Path, config: Config, resolver: Resolver) {
     (type, message) => getConsoleOutput(
       config.rootDir,
       !!config.verbose,
-      // 4 = the console call is burried 4 stack frames deep
+      // 4 = the console call is buried 4 stack frames deep
       BufferedConsole.write([], type, message, 4),
     ),
   );

packages/jest-config/src/index.js

@@ -15,6 +15,7 @@ const loadFromFile = require('./loadFromFile');
 const loadFromPackage = require('./loadFromPackage');
 const normalize = require('./normalize');
 const setFromArgv = require('./setFromArgv');
+const {getTestEnvironment} = require('./utils');
 
 const readConfig = (argv: Object, packageRoot: string) =>
   readRawConfig(argv, packageRoot)
@@ -60,6 +61,7 @@ const readRawConfig = (argv, root) => {
 };
 
 module.exports = {
+  getTestEnvironment,
   normalize,
   readConfig,
 };