Setup Gulp to open Karma debug page directly


By default Karma doesn’t open the debug page directly and it doesn’t have a configuration to allow that.

Using the default Karma settings to run the tests in a browser is a bit annoying because it requires to always keep clicking the debug button - which will open a new tab and eventually the tests start running. Instead, I would like Gulp to directly open the debug.html page when the Gulp task starts.

The following setup allows that:

  • We’ll need browser sync
  • In Karma config we won’t specify any browsers to launch automatically because we’ll use browser-sync for that. Thus inside karma.conf.js set browsers: []
  • We’ll add a few lines of code in our gulpfile to dynamically capture the url address of Karma’s web server
var karmaInstance = new KarmaServer(karmaConfig, _onKarmaExit);

// get Karma's web server instance
var karmaWebServer = karmaInstance.get('webServer');

// listen on listening event and grab the address to pass to browserSync
karmaWebServer.on('listening', _getConnectionDetails);

function _getConnectionDetails() {
  var connectionDetails = karmaWebServer.address();
  var debugAddress = [

  • Pass the address to browser-sync and open a browser instance

Running the project

1. git clone git@github.com:efidiles/karma-debug-with-browser-sync.git .
2. npm install
3. npm test

Karma’s /debug.html will now open in your browser.