How to Use Node Test Runner in Node.js: Simple Guide

Use the built-in node:test module in Node.js by importing it and writing test functions with test(). Run your test file with node --test to execute tests and see results in the console.

Syntax

The Node.js test runner uses the test() function to define tests. You import it from the node:test module. Each test has a name and a callback function where you write assertions.

Assertions are made using the assert module to check if values meet expectations.

javascript

import test from 'node:test';
import assert from 'node:assert';

test('test name', () => {
  assert.strictEqual(actual, expected);
});

Example

This example shows a simple test that checks if 2 + 2 equals 4 using the Node.js test runner.

javascript

import test from 'node:test';
import assert from 'node:assert';

test('simple addition test', () => {
  const result = 2 + 2;
  assert.strictEqual(result, 4);
});

Output

1 test passed

Common Pitfalls

Common mistakes include forgetting to import test or assert, not running tests with node --test, or writing asynchronous tests without handling promises properly.

Also, avoid using console.log for test results; rely on assertions instead.

javascript

/* Wrong: Missing import and running with plain node */
// test('fail test', () => {
//   assert.strictEqual(1, 1);
// });

/* Right: Import and run with node --test */
import test from 'node:test';
import assert from 'node:assert';

test('pass test', () => {
  assert.strictEqual(1, 1);
});

Quick Reference

• Import test and assert: import test from 'node:test'; import assert from 'node:assert';
• Define tests: test('name', () => { ... })
• Run tests: Use node --test yourfile.js
• Assertions: Use assert.strictEqual() and other assert methods

Key Takeaways

Use the built-in node:test module with test() to write tests in Node.js.

Run tests using the command node --test yourfile.js to see results.

Always import both test and assert modules before writing tests.

Write clear assertions with assert.strictEqual() to verify behavior.

Avoid running test files with plain node; use the --test flag.