Karma launcher and preprocessor for Electron

This was written to allow for directly testing in Electron where we might want require to work automatically

Features:

• Tested via CI on Linux and Windows
• Support for Node.js integration in the renderer process (e.g. node_modules, __filename, relative paths for require)
• Support for hidden browser windows
• Support for isolated test runs to prevent cookie/localStorage pollution

Requirements:

• karma>=1.1.0 to work within electron's security policy for shared context between parent/child windows
  • See karma-runner/karma#1984 for more information

Notices:

• This plugin has been tested against electron@{0.x,1,5,6,7,8,9,11,12,14,15,20} and should support the latest version
• This plugin is best suited for testing the renderer portion of an electron application
  • For testing a full application, see electron's documentation on Selenium and WebDriver
  • https://github.com/electron/electron/blob/v1.3.6/docs/tutorial/using-selenium-and-webdriver.md

contextIsolation has been set to true by default, which limits interaction with require and postMessage

To resolve these issues, please see the latest Getting Started instructions

For more information, see #50

We have corrected inaccuracies with file:// behavior from Electron. For example:

• __filename is now Karma's context.html
• Relative paths for require resolve from Karma's context.html directory

We have transferred support for this to the option client.loadScriptsViaRequire which loads scripts via require and has the original expected Node.js behavior

For more information, see #11

On a project that has been set up with karma init already, install the module via:

# Install our module and `electron`
npm install karma-electron electron

Then, configure the module with the following:

Note: Due to electron@12 postMessage limitations, we set BrowserWindow#webPreferences.nativeWindowOpen to true by default (see #50 for more info)

// Inside `karma.conf.js`
browsers: ['Electron']

// DEV: `useIframe: false` is for launching a new window instead of using an iframe
//   In Electron, iframes don't get `nodeIntegration` priveleges yet windows do
client: {
  useIframe: false
}

Then, we can run Karma:

karma start

By default, we try to use the minimal Electron configuration to avoid any assumptions about your repo

As a result, we need to define a custom launcher to match your Electron configuration

To add Node.js integration support (e.g. require), use the following:

// Inside `karma.conf.js`
// Define our custom launcher for Node.js support
customLaunchers: {
  CustomElectron: {
    base: 'Electron',
    browserWindowOptions: {
      // DEV: More preferentially, should link your own `webPreferences` from your Electron app instead
      webPreferences: {
        // Preferred `preload` mechanism to expose `require`
        preload: __dirname + '/path/to/preload.js'

        // Alternative non-preload mechanism to expose `require`
        // nodeIntegration: true,
        // contextIsolation: false

        // nativeWindowOpen is set to `true` by default by `karma-electron` as well, see #50
      }
    }
  }
}

// Use our custom launcher
browsers: ['CustomElectron']

// DEV: preprocessors is for backfilling `__filename` and local `require` paths
preprocessors: {
  '**/*.js': ['electron']
},

// DEV: `useIframe: false` is for launching a new window instead of using an iframe
//   In Electron, iframes don't get `nodeIntegration` priveleges yet windows do
client: {
  useIframe: false
}

Then, we can run Karma:

karma start

• ELECTRON_BIN - Override path to use for electron
  • By default, we will use path given by electron

Example:

ELECTRON_BIN=/usr/bin/electron karma start

We support the following configurations:

• client Object - Container for configuring child windows loaded from Karma
  • __filenameOverride String - Override __filename to be another path (e.g. /path/to/my-index.html)
    • This will also affect __dirname and module.filename as those are derived from __filename
    • By default, __filename will point to Karma's context.html
  • loadScriptsViaRequire Boolean - Load scripts via require instead of <script src=
    • This sets __filename, __dirname, and module to match the script instead of Karma's context.html
    • By default, this is false and we directly load the original scripts content

Example:

// Inside `karma.conf.js`
module.exports = function (config) {
  config.set({
    client: {
      // DEV: These 2 options aren't typically used together
      //   This is for demonstration purposes

      // Override top level `__filename` to be `/home/.../my-electron-app/index.html`
      //   where `__dirname` is `/home/.../my-electron-app`
      __filenameOverride: __dirname + '/index.html',

      // Use `require` instead of `<script src=` to load scripts
      loadScriptsViaRequire: true
    }
  });
};

We support configuration via Karma's custom launcher inheritance:

• flags Array - List of Chromium flags to alter Electron's behavior
  • https://github.com/atom/electron/blob/v0.36.9/docs/api/chrome-command-line-switches.md
• userDataDir String - Directory to store cookies/localStorage information
  • By default, this is a random directory generated by Karma (e.g. /tmp/karma-5355024)
• require String - Path to a main Electron process file to require before calling app.on('ready')
• browserWindowOptions Object - Parameters to pass to new BrowserWindow
  • This will be serialized to JSON so any functions or other live data will be lost
• loadURLOptions Object - Parameters to pass to BrowserWindow.loadURL
  • This will be serialized to JSON so any functions or other live data will be lost

Example:

// Inside `karma.conf.js`
module.exports = function (config) {
  config.set({
    // Specify usage of our custom launcher
    browsers: ['CustomElectron'],

    // Define a custom launcher which inherits from `Electron`
    customLaunchers: {
      CustomElectron: {
        base: 'Electron',
        userDataDir: __dirname + '/.electron',
        browserWindowOptions: {
          show: true
          // nativeWindowOpen is set to `true` by default by `karma-electron` as well, see #50
        },
        require: __dirname + '/main-fixtures.js'
      }
    }
  });
};

In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint via npm run lint and test via npm test.

Support this project and others by twolfson via donations.

http://twolfson.com/support-me

As of Mar 03 2016, Todd Wolfson has released this repository and its contents to the public domain.

It has been released under the UNLICENSE.