karma-mocha

What is karma-mocha?

The karma-mocha npm package is a plugin that allows you to use the Mocha testing framework with the Karma test runner. It enables you to run Mocha tests in various browsers and provides a seamless integration between Karma and Mocha.

What are karma-mocha's main functionalities?

Running Mocha Tests with Karma

This configuration file sets up Karma to use the Mocha framework. It specifies the test files to include and the browser to run the tests in. The 'singleRun' option ensures that Karma runs the tests once and then exits.

module.exports = function(config) {
  config.set({
    frameworks: ['mocha'],
    files: [
      'test/**/*.js'
    ],
    browsers: ['Chrome'],
    singleRun: true
  });
};

Using Mocha Hooks

This code demonstrates the use of Mocha hooks (before, after, beforeEach, afterEach) within a test suite. These hooks allow you to set up preconditions and clean up after tests.

describe('Array', function() {
  before(function() {
    // runs before all tests in this block
  });

  after(function() {
    // runs after all tests in this block
  });

  beforeEach(function() {
    // runs before each test in this block
  });

  afterEach(function() {
    // runs after each test in this block
  });

  it('should start empty', function() {
    var arr = [];
    assert.equal(arr.length, 0);
  });
});

Asynchronous Testing

This code demonstrates how to write asynchronous tests in Mocha. The 'done' callback is used to signal that the test is complete. If an error occurs, it is passed to the 'done' callback.

describe('User', function() {
  it('should save without error', function(done) {
    var user = new User('Luna');
    user.save(function(err) {
      if (err) done(err);
      else done();
    });
  });
});

Other packages similar to karma-mocha

karma-jasmine

The karma-jasmine package is a plugin that allows you to use the Jasmine testing framework with the Karma test runner. Like karma-mocha, it enables you to run tests in various browsers. Jasmine is known for its behavior-driven development (BDD) style and comes with a rich set of matchers and utilities.

karma-qunit

The karma-qunit package is a plugin that integrates the QUnit testing framework with the Karma test runner. QUnit is a powerful, easy-to-use JavaScript unit testing framework. It is used by the jQuery project and is known for its simplicity and ease of use.

karma-chai

The karma-chai package allows you to use the Chai assertion library with the Karma test runner. Chai can be used with different testing frameworks like Mocha, Jasmine, and QUnit. It provides a variety of assertion styles, including BDD and TDD, making it a versatile choice for testing.

README

karma-mocha

Adapter for the Mocha testing framework.

Installation

Install karma-mocha and mocha into to your project via npm:

$ npm install karma-mocha mocha --save-dev

karma-mocha should work with any version of mocha.

Since karma-mocha is an adapter for Karma, you likely have it installed already, but in case you don't:

$ npm install karma --save-dev

If you're having trouble, Karma provides detailed instructions on installation.

Configuration

Following code shows the default configuration...

// karma.conf.js
module.exports = function(config) {
  config.set({
    frameworks: ['mocha'],

    files: [
      '*.js'
    ]
  });
};

If you want to pass configuration options directly to mocha you can do this in the following way

// karma.conf.js
module.exports = function(config) {
  config.set({
    frameworks: ['mocha'],

    files: [
      '*.js'
    ],

    client: {
      mocha: {
        // change Karma's debug.html to the mocha web reporter
        reporter: 'html',

        // require specific files after Mocha is initialized
        require: [require.resolve('bdd-lazy-var/bdd_lazy_var_global')],

        // custom ui, defined in required file above
        ui: 'bdd-lazy-var/global',
      }
    }
  });
};

If you want run only some tests matching a given pattern you can do this in the following way

karma start &
karma run -- --grep=<pattern>

or

module.exports = function(config) {
  config.set({
    ...
    client: {
      mocha: {
        grep: '<pattern>', // passed directly to mocha
        ...
      }
      ...
    }
  });
};

If you want to expose test properties specific to mocha, you can use the expose option:

module.exports = function(config) {
  config.set({
    ...
    client: {
      mocha: {
        expose: ['body'] // This will be exposed in a reporter as `result.mocha.body`
        ...
      }
      ...
    }
  });
};

If you already have a configuration for Mocha in an opts file, you can use the opts option:

module.exports = function(config) {
  config.set({
    ...
    client: {
      mocha: {
        opts: 'test/mocha.opts' // You can set opts to equal true then plugin will load opts from default location 'test/mocha.opts'
        ...
      }
      ...
    }
  });
};

Internals

On the end of each test karma-mocha passes to karma result object with fields:

• description Test title.
• suite List of titles of test suites.
• success True if test is succeed, false otherwise.
• skipped True if test is skipped.
• time Test duration.
• log List of errors.
• startTime Milliseconds since epoch that the test started
• endTime Milliseconds since epoch that the test ended
• assertionErrors List of additional error info:
  • name Error name.
  • message Error message.
  • actual Actual data in assertion, serialized to string.
  • expected Expected data in assertion, serialized to string.
  • showDiff True if it is configured by assertion to show diff.
• mocha An optional object listed if you use the expose option

This object will be passed to test reporter.

NB. the start and end times are added by the adapter whereas the duration is calculated by Mocha - as such they probably will not match arithmetically. Ie. endTime - startTime !== duration. These fields have been added so that timestamped reports can be matched up with other timestamped reports from the target device (eg. memory profiling data collected outside the browser)

---

For more information on Karma see the homepage.

Changelog

2.0.1 (2020-04-29)

Bug Fixes

• deps: Report fails without emit 'test end' event (#223) (1a8226c)

Features

• ci: enable semanitic-release (5a5b6d5)

• Expose 'pending' status (e847121), closes #109

• Update Node.js versions (fd64f5b)

BREAKING CHANGES

• drop support for node 8

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