expect Archives | JS FAQ - JavaScript Guides Online

How to test exceptions and thrown errors in Jest

Jest testing for asynchronous functions includes handling promises, verifying promise rejections, and asserting error types. Tests can use rejects matcher or async/await syntax to check errors and successful data resolution. Chaining async functions in tests ensures correct data processing and error management.

Testing Frameworks

How to test promises in JavaScript

Testing Frameworksasync, expect, promises, testing

Testing frameworks like Jest, Mocha, and Jasmine natively support promises for handling asynchronous tests, lifecycle hooks, and parallel operations with Promise.all(). Features include timer mocks for controlling time and async iterators support, ensuring reliable, readable, and efficient async test execution.

Testing Frameworks

How to use assertions in JavaScript testing

Testing Frameworksassert, check, expect, testing

Precision and clarity in assertions improve test reliability by focusing on meaningful, core functionality outcomes. Use descriptive messages, group related assertions, and ensure tests verify observable effects. Employ community assertion libraries and handle async tests carefully to maintain robustness and readability.