# Pattern 1: Async test with fixture
@pytest.fixture
async def db_session():
    async with async_session() as session:
        yield session
        await session.rollback()

@pytest.mark.asyncio
async def test_create_item(db_session):
    item = await create_item(db_session, {"name": "test"})
    assert item.name == "test"

# Pattern 2: Parametrized tests
@pytest.mark.parametrize("input,expected", [
    ("valid", True),
    ("invalid", False),
])
def test_validation(input, expected):
    assert validate(input) == expected

# Pattern 3: Mock external service
@pytest.fixture
def mock_api(mocker):
    return mocker.patch("app.services.api.call", return_value={"success": True})

async def test_with_mock(mock_api, db_session):
    result = await service_that_calls_api(db_session)
    mock_api.assert_called_once()

// Pattern 1: Component test with testing-library
import { render, screen, fireEvent } from '@testing-library/react';

test('button click updates state', async () => {
  render(<MyComponent />);
  fireEvent.click(screen.getByRole('button'));
  expect(await screen.findByText('Updated')).toBeInTheDocument();
});

// Pattern 2: Mock hook
jest.mock('../hooks/useStore', () => ({
  useStore: () => ({
    items: [{ id: 1, name: 'Test' }],
    addItem: jest.fn(),
  }),
}));

// Pattern 3: Async operation test
test('fetches data on mount', async () => {
  render(<DataComponent />);
  expect(await screen.findByText('Loaded')).toBeInTheDocument();
});