Javascript testing full#
Get full code coverage reporting so you know what’s left to test. Run tests straight from your browser, right in Node.js, or against many browsers & platforms at the same time with the Intern test runner. Environments: What to consider when setting up a testing environment for React components. Write tests in JavaScript and TypeScript using any style you like (TDD, BDD, whatever).Recipes: Common patterns when writing tests for React components.Although it doesn’t provide a way to “shallowly” render a component without its children, a test runner like Jest lets you do this by mocking. This approach makes refactoring a breeze and also nudges you towards best practices for accessibility. React Testing Library is a set of helpers that let you test React components without relying on their implementation details. Jest provides a great iteration speed combined with powerful features like mocking modules and timers so you can have more control over how the code executes. While jsdom is only an approximation of how the browser works, it is often good enough for testing React components. Jest is a JavaScript test runner that lets you access the DOM via jsdom. If you’re testing a form, should its test also test the buttons inside of it? Or should a button component have its own test suite? Should refactoring a button ever break the form test?ĭifferent answers may work for different teams and products. How much to mock: With components, the distinction between a “unit” and “integration” test can be blurry.Other tools might use a real browser environment, but reduce the iteration speed and are flakier on a continuous integration server. Iteration speed vs Realistic environment: Some tools offer a very quick feedback loop between making a change and seeing the result, but don’t model the browser behavior precisely.When choosing testing tools, it is worth considering a few tradeoffs: While full end-to-end tests can be very useful to prevent regressions to important workflows, such tests are not concerned with React components in particular, and are out of the scope of this section. This documentation section focuses on testing strategies for the first case. Running a complete app in a realistic browser environment (also known as “end-to-end” tests).
Rendering component trees in a simplified test environment and asserting on their output.Broadly, they divide into two categories: There are a few ways to test React components.
You can test React components similar to testing other JavaScript code.
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