Karma vs Mocha: What are the differences?

Introduction

Here, we will present the key differences between Karma and Mocha, two popular JavaScript testing frameworks.

1. Test Runner and Browser Integration: Karma acts as a test runner and provides seamless browser integration, allowing you to run tests on multiple browsers simultaneously. Mocha, on the other hand, is a test framework, but it doesn't have built-in support for browser automation and requires additional tools like WebDriver for running tests in different browsers.

2. Testing Styles:

   • Karma primarily focuses on running tests written in various testing frameworks like Mocha, Jasmine, or QUnit, providing a test runner for these frameworks to execute tests in a browser environment.
   • Mocha is a more comprehensive testing framework that provides a syntax for writing tests, assertion libraries, and supports different styles of testing like BDD (Behavior-Driven Development) and TDD (Test-Driven Development) out of the box.

3. Parallel Execution: Karma allows parallel execution of tests across multiple browsers, improving test execution time for large test suites. Mocha, however, doesn't offer parallel execution by default and will run tests sequentially.

4. Code Coverage: Karma includes built-in code coverage reports, which can be generated during test execution, giving insights into the percentage of code covered by tests. Mocha itself doesn't provide code coverage functionality, but it can be integrated with other tools like Istanbul to generate code coverage reports.

5. Browser Refresh: Karma has a live-reload feature that automatically refreshes the browsers whenever the test or source code changes. Mocha doesn't have this functionality, requiring you to manually refresh the browser or use additional tools like nodemon.

6. Integration with Task Runners: Karma integrates well with task runners like Grunt or Gulp, allowing you to automate test execution along with other development tasks. Mocha, being a test framework, can also be integrated with task runners, but it requires additional configuration and setup.

In summary, Karma offers browser integration, parallel execution, code coverage, automatic browser refresh, and seamless integration with task runners. On the other hand, Mocha provides a comprehensive testing framework with different testing styles and can be integrated with Karma for browser testing.