tdd-with-agents

TDD with Agents

Enforce RED → GREEN → REFACTOR cycle across all implementation agents. Includes advanced testing patterns for E2E, load, mutation, and contract testing.

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Core Principle

Write the test FIRST. Watch it fail. Write minimal code to pass. Refactor with confidence.

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TDD Cycle (RED → GREEN → REFACTOR)

RED — Write Failing Test

• Write test for the behavior you want
• Run it → must fail (confirms test works)
• Test should be specific: one assertion per test

GREEN — Make It Pass

• Write minimal code to pass the test
• No extra features, no premature optimization
• If it feels hard → design problem; refactor test

REFACTOR — Improve Without Breaking

• Clean up code while tests stay green
• Extract functions, rename, remove duplication
• Tests are your safety net

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Testing by Layer

Backend (Hermes)

# Unit: service logic
def test_calculate_discount_applies_percentage():
    result = calculate_discount(100, 10)
    assert result == 90.0

# Integration: API endpoint
def test_get_user_returns_404_for_missing():
    response = client.get("/users/nonexistent")
    assert response.status_code == 404

# Database: repository
def test_user_repository_saves_and_retrieves():
    repo.save(User(id="1", name="Test"))
    assert repo.find("1").name == "Test"

Frontend (Aphrodite)

// Test behavior, not implementation
test('shows error message on invalid form', async () => {
  render(<LoginForm />)
  await userEvent.click(screen.getByText('Submit'))
  expect(screen.getByText('Email is required')).toBeInTheDocument()
})

Database (Demeter)

def test_migration_creates_users_table():
    alembic upgrade(head)
    assert inspector.has_table('users')

def test_migration_rollback_drops_table():
    alembic upgrade(head)
    alembic downgrade(-1)
    assert not inspector.has_table('users')

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Advanced Testing Patterns

E2E Testing (Playwright)

test('user can complete full signup flow', async ({ page }) => {
  await page.goto('/signup')
  await page.fill('[name="email"]', '[email protected]')
  await page.fill('[name="password"]', 'secure123')
  await page.click('button[type="submit"]')
  await expect(page.locator('.welcome-banner')).toBeVisible()
})