Node.js includes a built-in test runner for writing tests without external dependencies. Here's how to use it.
Basic Usage
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Subtests
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describe and it
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Hooks
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Skipping and Focusing
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Mocking
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Timers
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Assertions
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Snapshot Testing
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Coverage
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Test Configuration
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Running Tests
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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
Conclusion
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.