TDD Cycle (Red-Green-Refactor)

• Red: Write a failing test first
• Green: Write minimal code to pass the test
• Refactor: Improve code while keeping tests passing
• Repeat for each new feature

TDD Benefits

• Better code design and architecture
• Comprehensive test coverage
• Documentation through tests
• Confidence to refactor
• Fewer bugs in production
• Faster debugging
• Forces you to think about requirements

Test Structure (AAA)

test('should add two numbers', () => {
  // Arrange - Set up test data
  const a = 5;
  const b = 3;
  const calculator = new Calculator();
  
  // Act - Execute the code being tested
  const result = calculator.add(a, b);
  
  // Assert - Verify the result
  expect(result).toBe(8);
});

Best Practices

• Write one test at a time
• Keep tests simple and focused
• Test behavior, not implementation
• Use descriptive test names
• Follow the Arrange-Act-Assert pattern
• Make tests independent (no shared state)
• Test edge cases and error conditions
• Keep test code clean too

Common Testing Patterns