Testing Strategies for JavaScript Applications

Testing Strategies for JavaScript Applications

Testing is not optional. It's a critical practice that prevents bugs, enables refactoring, and gives you confidence in your code.

Unit Testing

Test individual functions and components in isolation. Use Jest or Vitest for fast, parallel test execution.

describe('calculateTotal', () => {
  it('should sum all items', () => {
    const items = [10, 20, 30];
    expect(calculateTotal(items)).toBe(60);
  });
});

Integration Testing

Test how components work together. Ensure data flows correctly between modules.

End-to-End Testing

Use Playwright or Cypress to test complete user workflows through the UI.

Test Coverage

Aim for meaningful coverage (70-80%), not 100%. Coverage is a metric, not a goal.

Mock External Dependencies

Mock APIs, databases, and external services to keep tests fast and independent.

Test Organization

Keep tests close to source code. Use clear, descriptive test names.

Continuous Integration

Run tests automatically on every commit. Fail the build if tests fail.

Performance Testing

Monitor test execution time. Slow tests are skipped tests.

Testing your code is not overhead. It's insurance against regression and a foundation for maintainability.