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Unlock the Power of Node.js Native Test Runner
Testing is no longer an afterthought in modern application development. In recent years, it has gained significant attention, and tools like Mocha, Jest, and Jasmine have been created to facilitate elaborate testing mechanisms. Node.js has taken a major leap forward by incorporating a native test runner into its core, starting from version 20. This tutorial will delve into the features of the Node.js native test runner, exploring concepts like mocks, spies, and stubs, and comparing it to other testing tools like Jest and Mocha.
Getting Started with the Native Test Runner
The native test runner is part of the Node core, making it easily accessible. To import it, simply run the command node --test. The assert module is used for making comparisons, similar to libraries like Jest. You can write tests using both test and assert, as shown below:
import { test, assert } from 'node:test';
test('my test', () => {
assert.ok(true);
});
Setting Up and Organizing Tests
To set up your tests, create a directory called native-test and run npm init -y to set up a new Node project. Create an src directory for your application code and a test directory for your test files. Update the test script in your package.json file to run your test files using node --test.
Advanced Features of the Native Node Test Runner
The native test runner offers advanced features like creating spies and stubs using the mock function, collecting test coverage, and using test reporters. You can create a spy to check the arguments passed to a function, its return value, and the exceptions thrown. Stubs replace the behavior of other functions with predefined values, making it ideal for isolated testing.
Mocking and Stubbing Dependencies for Isolated Testing
The mock function provides a way to mock and replace functions at runtime. You can create spies and stubs using this function. For example, you can create a spy to check how many times a function is called and test its arguments and output.
Creating a Testing Stub
Stubs are functions that replace the behavior of other functions with predefined values. You can use the mock function to create a stub to replace a function that makes network requests.
Code Coverage
Collecting code coverage is essential in testing, as it helps you understand the percentage of functions in different files that you have written tests for. You can collect code coverage using the --experimental-test-coverage flag.
Test Reporters
Test reporters allow you to format the output of your test. The native test runner supports three test reporters out of the box: tap, spec, and dot. You can change the test reporter by editing the test script in your package.json file.
Comparison with Other Test Runners: Jest and Mocha
The native test runner offers similar features to Jest and Mocha, but with some advantages. It is part of the Node core, making it faster and more optimized for Node. It also eliminates the need to keep up with the latest version of a testing framework.
Advantages of Using the Node.js Test Runner
The native test runner offers several advantages over other testing frameworks. It is faster, more optimized for Node, and eliminates the need to deliberate over what framework to use. It also implements some of the same methods as other test frameworks, making it easy for developers to transition.
By now, you should have a good understanding of the Node.js native test runner and how to write tests using it. With its advanced features and advantages, it’s definitely worth considering for your next project.