Node.js Test Runner Guide

Node.js includes a built-in test runner for writing tests without external dependencies. Here's how to use it.

Best Practices#

Structure:
✓ Use describe/it for organization
✓ Keep tests focused
✓ Use hooks for setup/cleanup
✓ Group related tests

Mocking:
✓ Mock external dependencies
✓ Restore mocks after tests
✓ Use timers mock for time
✓ Spy on methods

Assertions:
✓ Use strictEqual for primitives
✓ Use deepStrictEqual for objects
✓ Test error conditions
✓ Be specific in assertions

Avoid:
✗ Testing implementation details
✗ Shared mutable state
✗ Flaky tests
✗ Too many assertions per test

The Node.js test runner provides a complete testing solution without external dependencies. Use test or describe/it for organization, hooks for setup/cleanup, and the mock API for test doubles. Run with --test flag and add coverage with --experimental-test-coverage.

Node.js Test Runner Guide

Basic Usage#

Subtests#

describe and it#

Hooks#

Skipping and Focusing#

Mocking#

Timers#

Assertions#

Snapshot Testing#

Coverage#

Test Configuration#

Running Tests#

Best Practices#

Conclusion#

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