There are two possibilities in order to run unit tests with Karma in Cloud9 IDE:
Capture the browser manually on the local machine
http://<projectName>.<cloud9User>.c9.io/ in your browser.
Run Karma unit tests with PhantomJS in cloud9 IDE
PhantomJS must be installed with
npm install phantomjs.
karma.conf.js file (tried it out for the AngularJS foodme app) must include the following entries:
browsers = ['PhantomJS'];
hostname = process.env.IP;
port = process.env.PORT;
runnerPort = 0;