Error: You need to include some adapter that implements __karma__.start method

I'm trying to add some unit tests to one of my projects.

So far I've installed and configured karma, and have installed jasmine. I've one test file in my test/ folder.

The karma server has started, the browser page is ready, but karma run fails as follows:

$ karma run karma-conf.js 
[2014-06-14 15:19:11.046] [DEBUG] config - Loading config /foo/test/karma-conf.js
Waiting for previous execution...
Chrome 35.0.1916 (Linux) ERROR
  You need to include some adapter that implements __karma__.start method!

This error message doesn't Google well.

Is this something obvious, or do I need to provide more information?

It does seem like this is a very general error, however in my case the problem was either that I didn't run karma start from the correct folder, or that I didn't restart it after changing the configuration.

I'll leave this question open and hopefully it can become a resource for others who experience this error message.

If you name your karma config file karma.conf.js, you can simply type karma start.

Otherwise specify the filename karma start karmafile.js

(I was in the right directory, but was not specifying a file name.)

You need to run your karma run or whatever function in the folder where karma-conf.js is in.

In my case I had to rename the file to karma.conf.js then do karma start

I had a problem with karma.conf.js file code format:

files: [
    // Modules
    ,"client/bower_components/angular/angular.min.js"
    ,"client/bower_components/angular-mocks/angular-mocks.js"
    // App
    ,"client/app/app.module.js"
    // Test
    // ,"test/**/*.spec.js"
],

The extra comma in files array have cause this error:

You need to include some adapter that implements __karma__.start method!