jest-runtime

What is jest-runtime?

The jest-runtime package is part of the Jest testing platform. It is responsible for executing tests and their associated code within a controlled environment. It handles the evaluation of the test files, mocking of modules, and provides utilities for loading and running the tests.

What are jest-runtime's main functionalities?

Module Mocking

Allows you to mock modules to isolate your tests from their dependencies, providing a way to test modules in isolation.

jest.mock('moduleName');

Test Environment Setup

Enables you to programmatically create a test environment, including the haste map (module map) and the test runner, which can be used to execute test files.

const runtime = require('jest-runtime');
// Create a runtime to execute the test
runtime.createHasteMap(config).then(hasteMap => {
  const environment = new runtime.TestEnvironment(config);
  const runner = new runtime.TestRunner(environment, hasteMap.resolver);
  // Execute the test file
  runner.runTest(filePath);
});

Script Transformation

Provides the ability to transform scripts using Jest's built-in transformers or custom ones. This is useful for preprocessing files before they are executed in the test environment.

const runtime = require('jest-runtime');
// Create a new runtime instance
const jestRuntime = new runtime.ScriptTransformer(config);
// Transform a script
const transformedCode = jestRuntime.transformSource(filePath, fileContent, false);

Other packages similar to jest-runtime

mocha

Mocha is a feature-rich JavaScript test framework running on Node.js and in the browser, making asynchronous testing simple. It is similar to jest-runtime in that it provides a test environment and runner, but it does not include a built-in mocking library or script transformation capabilities.

jasmine

Jasmine is a behavior-driven development framework for testing JavaScript code. It does not require a DOM, and it has a clean, obvious syntax so that you can easily write tests. It is similar to jest-runtime in providing an environment for running tests, but it has a different assertion library and does not handle module mocking and script transformation in the same way.

ava

AVA is a test runner for Node.js with a concise API, detailed error output, and process isolation that lets you develop with confidence. AVA is similar to jest-runtime in that it can run tests in parallel and supports the latest JavaScript features, but it differs in its approach to mocking and does not provide a built-in mechanism for script transformation.

README

The README file is missing

Changelog

25.5.4

Fixes

• [jest-jasmine2] Don't run beforeAll / afterAll in skipped describe blocks (#9931)

Chore & Maintenance

• [jest-runtime] Do not warn when mutating require.cache (#9946)