问题:

How do I setup Karma to run my backend unit tests (written with Mocha)? If I add my backend test script to the files = [], it fails stating that require is undefined.

回答1:

You don't. Karma is only for testing browser-based code. If you have a project with mocha tests on the backend and karma/mocha on the front end, try editing your package.json under scripts to set test to: mocha -R spec && karma run karma.con

Then, if npm test returns true, you'll know it's safe to commit or deploy.

回答2:

It seems like it cannot be done (thanks @dankohn). Here is my solution using Grunt:

Karma: update your karma.conf.js file
- set autoWatch = false;
- set singleRun = true;
- set browsers = ['PhantomJS']; (to have inline results)
Grunt :
- npm install grunt-contrib-watch grunt-simple-mocha grunt-karma
- configure the two grunt tasks (see grunt file below)

Gruntfile.js:

module.exports = function (grunt) {
  grunt.loadNpmTasks('grunt-simple-mocha');
  grunt.loadNpmTasks('grunt-karma');

  grunt.initConfig({
    simplemocha: {
      backend: {
        src: 'test/server-tests.js'
      }
    },
    karma: {
      unit: {
        configFile: 'karma.conf.js'
      }
    }
  });

  // Default task.
  grunt.registerTask('default', ['simplemocha', 'karma']);
};

Grunt (optional): setup grunt-watch to start tests on changing the tested files or the specs itself.
run all using grunt command.