AVA vs Jest vs Mocha: What are the differences?

Introduction

Markdown is a lightweight markup language used to format text that can be easily converted into HTML for displaying on websites. In this task, we will format the content as Markdown code and provide key differences between AVA, Jest, and Mocha, which are popular JavaScript testing frameworks.

1. Test Runner: AVA is a concurrent test runner, meaning it runs test files simultaneously, reducing the overall execution time. On the other hand, Jest and Mocha both run tests sequentially, executing one test file at a time.

2. Mocking and Spying: Jest provides built-in mocking and spying functionality, making it easier to create mocks and spies for testing purposes. Although Mocha also has some libraries that offer similar functionality, it lacks native support for these features. AVA, too, does not have built-in mocking and spying capabilities.

3. Configurability: Mocha provides extensive configurability options, allowing developers to customize the testing environment according to their needs. Jest also offers a good level of configurability with a wide range of configuration options. In contrast, AVA, although flexible, has a more opinionated and minimalistic configuration approach.

4. Parallel Test Execution: AVA allows tests to run in parallel by default, utilizing the full potential of modern multi-core systems. Jest, while it does support parallel execution, requires additional configuration to operate in parallel effectively. Mocha, on the other hand, executes tests sequentially and does not have built-in support for parallel execution.

5. Assertion Library: Jest comes with its own assertion library, which provides a wide range of built-in matchers for making assertions in tests. Mocha does not have an assertion library by default but can be combined with libraries like Chai or Should.js to achieve the same functionality. AVA, similar to Mocha, does not include an assertion library but can be used with third-party libraries like Chai or Power Assert.

6. Test Watcher: When running tests, Jest includes a built-in watch mode that automatically reruns tests whenever changes are detected, making it convenient during development. Mocha and AVA, on the other hand, do not have a built-in test watcher, requiring the use of additional tools like nodemon or chokidar.

In summary, AVA differentiates itself by providing concurrent test execution, but lacks built-in mocking and spying support. Jest offers extensive mocking and spying capabilities with a wide range of configuration options, along with a built-in assertion library. Mocha, a highly configurable testing framework, lacks features like native mocking and spying support and parallel test execution.