TDD Testing Skill

When to Use

• Qualquer nova feature implementation
• Bug fixes
• Quando quer confidence que código funciona

TDD Cycle

Phase 1: RED - Write Failing Test

def test_user_creation():
    user_service = UserService(db, cache)
    user = user_service.create_user({
        "email": "test@example.com",
        "name": "Test User"
    })
    assert user.id is not None
    assert user.email == "test@example.com"

Phase 2: GREEN - Minimal Code to Pass

class UserService:
    async def create_user(self, data):
        user = User(**data)
        await self.db.add(user)
        return user

Phase 3: REFACTOR - Improve Without Breaking

class UserService:
    async def create_user(self, data):
        # Add validation
        self.validate_email(data["email"])
        
        # Add deduplication
        existing = await self.db.query(User).filter(
            User.email == data["email"]
        ).first()
        if existing:
            raise UserAlreadyExists()
        
        user = User(**data)
        await self.db.add(user)
        return user

Best Practices

• 1 test → 1 feature
• Keep tests focused and small
• Test behavior, not implementation
• Rerun tests frequently
• Use fixtures for setup
• Mock external dependencies

Tools Needed

• unittest / pytest
• Mock (for dependencies)
• Faker (for test data)

Success Metrics

• 80% code coverage

• All tests pass
• Tests run in <30 seconds
• No flaky tests