Nock
Nock is a JavaScript library for mocking HTTP requests in Node.js applications, primarily used for testing. It intercepts HTTP requests made by code and allows developers to define mock responses, enabling isolated unit and integration tests without relying on external APIs or services. This helps simulate various server behaviors, such as success, error, or timeout responses, in a controlled testing environment.
Developers should learn Nock when building or testing Node.js applications that make HTTP calls to external APIs, as it ensures tests are fast, reliable, and independent of network conditions or third-party services. It is particularly useful for unit testing API clients, mocking backend services during development, and handling edge cases like rate limiting or server errors without hitting real endpoints.