Writing Unit Tests in Node.js Using Jest

As software complexity increases, the likelihood of bugs rises, making manual testing unreliable and necessitating unit testing to validate individual components independently. This article provides a comprehensive guide on writing high-quality unit tests in Node.js utilizing the Jest framework, including installation, setup, and the creation of test files. It explores the testing of both synchronous and asynchronous code, highlighting how Jest's built-in features, such as mock functions and matchers like `resolves`, support efficient testing processes. The article contrasts Test-Driven Development (TDD) and Behavior-Driven Development (BDD) methodologies, illustrating their implementation in Jest, and compares Jest with Mocha, noting Jest's out-of-the-box functionality versus Mocha's need for configuration. Ultimately, the guide offers insights into Jest's capabilities for creating reliable software, stressing its performance advantages and built-in tools for testing, while also acknowledging Mocha as an alternative for more customizable testing environments.