Error trying to execute tests with Karma - Uncaught ReferenceError: require is not defined

Question

I am trying to ran tests using karma and jasmine, but I am facing this "Uncaught ReferenceError: require is not defined" error. Sorry... could you help me to figure out what am I doing wrong?

1. Please see my environment, where this error is happening, and directory structure is:

   myproj
   |_ tests
   |  |_ example_spec.js
   |
   |_ karma-conf.js
   |_ package.json
   

2. The example_spec.js file has following code:

   var chai = require('chai');
   var expect = chai.expect;
   
   describe('Given an array', function () {
     'use strict';
     describe('the method push', function () {
       it('should add an element', function () {
         var arr = [];
         arr.push("hello");
         expect(arr.length).to.equal(1);
         expect(arr).to.contain("hello");
       });
     });
   });
   

3. The package.json file has following dependencies:

   "devDependencies": {
     "grunt": "~0.4.5",
     "frisby": "~0.8.5",
     "load-grunt-config": "~0.16.0",
     "karma": "~0.12.31",
     "karma-jasmine": "~0.3.5",
     "karma-chrome-launcher": "~0.1.7",
     "karma-junit-reporter": "~0.2.2",
     "chai": "~2.2.0",
     "chai-as-promised": "~4.3.0",
     "jasmine-node-karma": "~1.6.1",
     "jasmine-node": "~1.14.5"
   }
   

4. Then, I tried to ran test following command:

   ./node_modules/karma/bin/karma start karma-conf.js
   

5. And following reference error is raised:

   Uncaught ReferenceError: require is not defined
   at /home/dir/dir/myproj/tests/example_spec.js:4
   

Note: Mocha is not involved in this project.