feature/add-first-class-debugging-support-for-tests

packages/react-scripts/bin/react-scripts.js

@@ -1,5 +1,6 @@
 #!/usr/bin/env node
 var spawn = require('cross-spawn');
+var getDebugFlag = require('../utils/getDebugFlag');
 var script = process.argv[2];
 var args = process.argv.slice(3);
 
@@ -8,9 +9,14 @@ case 'build':
 case 'eject':
 case 'start':
 case 'test':
+  var scriptArgs = [require.resolve('../scripts/' + script)].concat(args);
+  var debugFlag = getDebugFlag(args);
+  if (debugFlag) {
+    scriptArgs.unshift(debugFlag);
+  }
   var result = spawn.sync(
     'node',
-    [require.resolve('../scripts/' + script)].concat(args),
+    scriptArgs,
     {stdio: 'inherit'}
   );
   process.exit(result.status);

packages/react-scripts/config/jest/babelJestDebugConfig.js

@@ -0,0 +1,3 @@
+const babelJestDefaultConfig = require('./babelJestDefaultConfig');
+const assign = require('object-assign');
+module.exports = assign(babelJestDefaultConfig, { sourceMaps: true });

packages/react-scripts/config/jest/babelJestDefaultConfig.js

@@ -0,0 +1,4 @@
+module.exports = {
+  presets: [require.resolve('babel-preset-react-app')],
+  babelrc: false
+}

packages/react-scripts/config/jest/babelTransform.js

@@ -7,8 +7,5 @@
  */
 
 const babelJest = require('babel-jest');
-
-module.exports = babelJest.createTransformer({
-  presets: [require.resolve('babel-preset-react-app')],
-  babelrc: false
-});
+const babelJestDebugConfig = require('./babelJestDebugConfig');
+module.exports = babelJest.createTransformer(babelJestDebugConfig);

packages/react-scripts/config/jest/babelTransformDebug.js

@@ -0,0 +1,11 @@
+/**
+ * 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.
+ */
+
+const babelJest = require('babel-jest');
+const babelJestDebugConfig = require('./babelJestDebugConfig');
+module.exports = babelJest.createTransformer(babelJestDebugConfig);

packages/react-scripts/scripts/eject.js

@@ -59,7 +59,8 @@ prompt(
     path.join('config', 'jest', 'fileTransform.js'),
     path.join('scripts', 'build.js'),
     path.join('scripts', 'start.js'),
-    path.join('scripts', 'test.js')
+    path.join('scripts', 'test.js'),
+    path.join('utils', 'getDebugFlag.js')
   ];
 
   // Ensure that the app folder is clean and we won't override any files
@@ -122,11 +123,10 @@ prompt(
   console.log(cyan('Configuring package.json'));
   // Add Jest config
   console.log('  Adding ' + cyan('Jest') + ' configuration');
-  appPackage.jest = createJestConfig(
-    filePath => path.join('<rootDir>', filePath),
-    null,
-    true
-  );
+  appPackage.jest = createJestConfig({
+    resolve: filePath => path.join('<rootDir>', filePath),
+    isEjecting: true
+  });
 
   // Add Babel config
 

packages/react-scripts/scripts/test.js

@@ -9,6 +9,11 @@
  */
 // @remove-on-eject-end
 
+/**
+ * Greetings! If you are here attempting to start a debugging session, please
+ * ensure that your debugger of choice is configured to enable source maps,
+ * otherwise your code may appear mangled by babel!
+ */
 process.env.NODE_ENV = 'test';
 process.env.PUBLIC_URL = '';
 
@@ -20,21 +25,32 @@ require('dotenv').config({silent: true});
 
 const jest = require('jest');
 const argv = process.argv.slice(2);
+const debugFlag = require('../utils/getDebugFlag')(argv);
+const isDebug = !!debugFlag;
+const isRunInBand = argv.indexOf('--runInBand') > -1 || argv.indexOf('-i') > -1
 
 // Watch unless on CI or in coverage mode
-if (!process.env.CI && argv.indexOf('--coverage') < 0) {
+if (!process.env.CI && argv.indexOf('--coverage') < 0 && !isDebug) {
   argv.push('--watch');
 }
 
+// Force debug into single worker
+if (isDebug) {
+  if (!isRunInBand) {
+    argv.push('--runInBand')
+  }
+  argv.splice(argv.indexOf(debugFlag), 1)
+}
+
 // @remove-on-eject-begin
 // This is not necessary after eject because we embed config into package.json.
 const createJestConfig = require('../utils/createJestConfig');
 const path = require('path');
 const paths = require('../config/paths');
-argv.push('--config', JSON.stringify(createJestConfig(
-  relativePath => path.resolve(__dirname, '..', relativePath),
-  path.resolve(paths.appSrc, '..'),
-  false
-)));
+argv.push('--config', JSON.stringify(createJestConfig({
+  resolve: relativePath => path.resolve(__dirname, '..', relativePath),
+  rootDir: path.resolve(paths.appSrc, '..'),
+  isDebug: isDebug
+})));
 // @remove-on-eject-end
 jest.run(argv);

packages/react-scripts/template/README.md

@@ -48,6 +48,7 @@ You can find the most recent version of this guide [here](https://github.com/fac
   - [Disabling jsdom](#disabling-jsdom)
   - [Experimental Snapshot Testing](#experimental-snapshot-testing)
   - [Editor Integration](#editor-integration)
+  - [Debugging](#debugging)
 - [Developing Components in Isolation](#developing-components-in-isolation)
 - [Making a Progressive Web App](#making-a-progressive-web-app)
 - [Deployment](#deployment)
@@ -480,7 +481,7 @@ Now you are ready to use the imported React Bootstrap components within your com
 
 Flow is a static type checker that helps you write code with fewer bugs. Check out this [introduction to using static types in JavaScript](https://medium.com/@preethikasireddy/why-use-static-types-in-javascript-part-1-8382da1e0adb) if you are new to this concept.
 
-Recent versions of [Flow](http://flowtype.org/) work with Create React App projects out of the box. 
+Recent versions of [Flow](http://flowtype.org/) work with Create React App projects out of the box.
 
 To add Flow to a Create React App project, follow these steps:
 
@@ -938,10 +939,18 @@ This feature is experimental and still [has major usage issues](https://github.c
 
 ### Editor Integration
 
-If you use [Visual Studio Code](https://code.visualstudio.com), there is a [Jest extension](https://github.com/orta/vscode-jest) which works with Create React App out of the box. This provides a lot of IDE-like features while using a text editor: showing the status of a test run with potential fail messages inline, starting and stopping the watcher automatically, and offering one-click snapshot updates. 
+If you use [Visual Studio Code](https://code.visualstudio.com), there is a [Jest extension](https://github.com/orta/vscode-jest) which works with Create React App out of the box. This provides a lot of IDE-like features while using a text editor: showing the status of a test run with potential fail messages inline, starting and stopping the watcher automatically, and offering one-click snapshot updates.
 
 ![VS Code Jest Preview](https://cloud.githubusercontent.com/assets/49038/20795349/a032308a-b7c8-11e6-9b34-7eeac781003f.png)
 
+### Debugging
+
+You can easily debug your tests by passing the usual debug flags to `npm test`.
+
+For example:
+  - Run `npm test -- --debug-brk` to attach the the debugger using your debugger of choice (vscode, webstorm, etc).
+  - Run `npm test -- debug` to enter the CLI debugger.
+
 ## Developing Components in Isolation
 
 Usually, in an app, you have a lot of UI components, and each of them has many different states.
@@ -1173,16 +1182,16 @@ GitHub Pages doesn't support routers that use the HTML5 `pushState` history API
 ### Heroku
 
 Use the [Heroku Buildpack for Create React App](https://github.com/mars/create-react-app-buildpack).<br>
-You can find instructions in [Deploying React with Zero Configuration](https://blog.heroku.com/deploying-react-with-zero-configuration). 
+You can find instructions in [Deploying React with Zero Configuration](https://blog.heroku.com/deploying-react-with-zero-configuration).
 
 #### Resolving "Module not found: Error: Cannot resolve 'file' or 'directory'"
 
 Sometimes `npm run build` works locally but fails during deploy via Heroku with an error like this:
 
-```  
+```
 remote: Failed to create a production build. Reason:
-remote: Module not found: Error: Cannot resolve 'file' or 'directory' 
-MyDirectory in /tmp/build_1234/src  
+remote: Module not found: Error: Cannot resolve 'file' or 'directory'
+MyDirectory in /tmp/build_1234/src
 ```
 
 This means you need to ensure that the lettercase of the file or directory you `import` matches the one you see on your filesystem or on GitHub.

packages/react-scripts/utils/createJestConfig.js

@@ -12,11 +12,18 @@
 const fs = require('fs');
 const paths = require('../config/paths');
 
-module.exports = (resolve, rootDir, isEjecting) => {
+module.exports = (opts) => {
+  const resolve = opts.resolve;
+  const rootDir = opts.rootDir || null;
+  const isEjecting = opts.isEjecting || false;
+  const isDebug = opts.isDebug || false;
+
   // Use this instead of `paths.testsSetup` to avoid putting
   // an absolute filename into configuration after ejecting.
   const setupTestsFile = fs.existsSync(paths.testsSetup) ? '<rootDir>/src/setupTests.js' : undefined;
-
+  const babelTransform = isEjecting
+    ? '<rootDir>/node_modules/babel-jest'
+    : resolve('config/jest/babelTransform' + (isDebug ? 'Debug' : '') + '.js')
   // TODO: I don't know if it's safe or not to just use / as path separator
   // in Jest configs. We need help from somebody with Windows to determine this.
   const config = {
@@ -29,9 +36,7 @@ module.exports = (resolve, rootDir, isEjecting) => {
     testEnvironment: 'node',
     testURL: 'http://localhost',
     transform: {
-      '^.+\\.(js|jsx)$': isEjecting ?
-        '<rootDir>/node_modules/babel-jest'
-        : resolve('config/jest/babelTransform.js'),
+      '^.+\\.(js|jsx)$': babelTransform,
       '^.+\\.css$': resolve('config/jest/cssTransform.js'),
       '^(?!.*\\.(js|jsx|css|json)$)': resolve('config/jest/fileTransform.js'),
     },

packages/react-scripts/utils/getDebugFlag.js

@@ -0,0 +1,25 @@
+/**
+ * Copyright (c) 2015-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.
+ */
+
+const DEBUG_FLAGS = [ 'debug', '--debug-brk', '--inspect' ];
+
+module.exports = function getDebugFlag(argv) {
+  for (var i in argv) {
+    if (argv.hasOwnProperty(i)) {
+      for (var j in DEBUG_FLAGS) {
+        if (DEBUG_FLAGS.hasOwnProperty(j)) {
+          if (argv[i] === DEBUG_FLAGS[j]) {
+            return DEBUG_FLAGS[j];
+          }
+        }
+      }
+    }
+  }
+  return null;
+}