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.