mocha-chrome
Requirements
mocha-chrome requires Node v8.0.0 or higher.
mocha-chrome is a development tool, which means you can use tools like NVM and nodenv to manage your installed versions, and temporarily switch to v8+ to run tests on your machine. Most modern CI environments also support specifying the version of Node to run.
Getting Started
To begin, you'll need to install mocha-chrome:
$ npm install mocha-chrome --save-devThen you'll need a local npm install of mocha:
$ npm install mocha --save-devTo run the tests, you'll need an HTML file with some basics:
<!doctype>
<html>
<head>
<title>Test</title>
<meta charset="utf-8">
<link rel="stylesheet" href="../../node_modules/mocha/mocha.css" />
<script src="../../node_modules/mocha/mocha.js"></script>
<script src="../../node_modules/chai/chai.js"></script>
</head>
<body>
<div id="mocha"></div>
<script>
expect = chai.expect;
// add tests here
mocha.run();
</script>
</body>
</html>You can then add your tests either through an external script file or inline within a <script> tag. Running the tests is easy, either with the CLI binary, or programmatically.
CLI
$ mocha-chrome --help
Usage
$ mocha-chrome <file.html> [options]
Options
--chrome-flags A JSON string representing an array of flags to pass to Chrome
--chrome-launcher Chrome launcher options (see https://github.com/GoogleChrome/chrome-launcher#launchopts)
--ignore-console Suppress console logging
--ignore-exceptions Suppress exceptions logging
--ignore-resource-errors Suppress resource error logging
--log-level Specify a log level; trace, debug, info, warn, error
--mocha A JSON string representing a config object to pass to Mocha
--no-colors Disable colors in Mocha's output
--reporter Specify the Mocha reporter to use
--timeout Specify the test startup timeout to use
--version
Examples
$ mocha-chrome test.html --no-colors
$ mocha-chrome test.html --reporter dot
$ mocha-chrome test.html --mocha '\{"ui":"tdd"\}'
$ mocha-chrome test.html --chrome-flags '["--some-flag", "--and-another-one"]'
$ mocha-chrome test.html --chrome-launcher.maxConnectionRetries=10Events
mocha-chrome is technically an event emitter. Due to the asynchronous nature of nearly every interaction with headless Chrome, a simple event bus is used to handle actions from the browser. You have access to those events if running mocha-chrome programatically.
Example usage can be found in both test.js and bin/mocha-chrome.
config
Fired to indicate that mocha-chrome should configure mocha.
ended
Fired when all tests have ended.
Parameters
stats : object - A Mocha stats object. eg:
{
suites: 1,
tests: 1,
passes: 1,
pending: 0,
failures: 0,
start: '2017-08-03T02:12:02.007Z',
end: '2017-08-03T02:12:02.017Z',
duration: 10
}
ready
Fired to indicate that the mocha script in the client has been loaded.
resourceFailed
Fired when a resource fails to load.
Parameters
data : object - An object containing information about the resource. eg:
{ url, method, reason }
started
Fired when a resource fails to load.
Parameters
tests : number - The number of tests being run.
width
Fired to indicate that mocha-chrome should inform mocha of the width of the current console/terminal.
Limitations
Reporters
Reporters are limited to those which don't use process.stdout.write to manipulate terminal output. eg. spec, xunit, etc. Examples of reporters which don't presently produce expected output formatting include dot and nyan. The cause of this limitation is the lack of a good means to pipe Mocha's built-in stdout.write through the Chrome Devtools Protocol to mocha-chrome.
Third-Party Reporters
Third party reporters are not currently supported, but support is planned. Contribution on that effort is of course welcome.
Cookies and the file:// Protocol
Chrome has long-since disabled cookies for files loaded via the file:// protocol. The once-available --enable-file-cookies has been removed and we're left with few options. If you're in need of cookie support for your local-file test, you may use the following snippet, which will shim document.cookie with very basic support:
Object.defineProperty(document, 'cookie', {
get: function () {
return this.value || '';
},
set: function (cookie) {
cookie = cookie || '';
const cutoff = cookie.indexOf(';');
const pair = cookie.substring(0, cutoff >= 0 ? cutoff : cookie.length);
const cookies = this.value ? this.value.split('; ') : [];
cookies.push(pair);
return this.value = cookies.join('; ');
}
});Continuous Integration
Circle CI
Running on Circle CI requires that Chrome is installed and running in the container your tests are running within. Please refer to this article for details: https://discuss.circleci.com/t/installing-chrome-inside-of-your-docker-container/9067. Alternatively, you can use a pre-built CircleCI image with browsers installed. You'll have to choose a tag with the -browsers suffix from the full tag list.
Travis CI
Please refer to the "Running it all on Travis CI" portion of the guide on Automated testing with Headless Chrome from Google. Though the article primarily addresses Karma, the setup for Travis CI is identical.
As of January 8th, 2018, Travis CI has upgraded from Trusty -> Xenial to address the Meltdown security vulnerability. There are issues with Chrome in Xenial that can currently be worked around with sudo: required. At some point this workaround may be removable. For the near term, please add sudo: required to Travis CI configuration files. See travis-ci/travis-ci#8836. Credit: @smalls.
Testing mocha-chrome
$ npm testYep, that's it.
Contributing
We welcome your contributions! Please have a read of CONTRIBUTING.
Attribution
I'd like to thank @nathanboktae for his work on mocha-phantomjs and mocha-phantomjs-core; two projects I've used extensively over the years, and from which the inspiration for this module originates. Many of the nuances of working with mocha in a hosted or connected browser environment were solved within mocha-phantomjs-core and I am personally grateful.