Jest is a JavaScript testing framework developed by Facebook. It is widely used for testing JavaScript code, especially for applications built with popular Javascript-based frontend frameworks such as React, Angular and Vue.js.
Jest is designed to be easy use. It provides a comprehensive testing solution and includes features such as test runners, assertions, mocking and code coverage reporting.
Snapshot testing is also supported, which is similar to visual regression testing on browsers.
The most important benefits into using Jest are:
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Mocking
Jest provides powerful mocking capabilities to isolate units of code, during testing. You can mock various aspects, for example functions, modules and third-party dependencies.
The benefits of using mocks is that you can control what is returned to a specific piece of code. You can write various tests with multiple mocking responses and make sure your test logic handles all cases.
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Code Coverage
Jest comes with built-in support to report code coverage. Jest will generate detailed reports, indicating which parts of the codebase are covered by tests. This helps to identify areas that may need additional testing.
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Extensibility
Jest is designed to be extensible, which allows developers to customize and extend its functionality. There's a community of Jest developers, creating very useful Jest plugins.
TestingBot provides code examples for Jest and Puppeteer testing, as well as Playwright and Jest testing.
