## Test Organization

### Directory Structure

```
tests/
├── conftest.py                 # Shared fixtures
├── __init__.py
├── unit/                       # Unit tests
│   ├── __init__.py
│   ├── test_models.py
│   ├── test_utils.py
│   └── test_services.py
├── integration/                # Integration tests
│   ├── __init__.py
│   ├── test_api.py
│   └── test_database.py
└── e2e/                        # End-to-end tests
    ├── __init__.py
    └── test_user_flow.py
```

### Test Classes

```python
class TestUserService:
    """Group related tests in a class."""

    @pytest.fixture(autouse=True)
    def setup(self):
        """Setup runs before each test in this class."""
        self.service = UserService()

    def test_create_user(self):
        """Test user creation."""
        user = self.service.create_user("Alice")
        assert user.name == "Alice"

    def test_delete_user(self):
        """Test user deletion."""
        user = User(id=1, name="Bob")
        self.service.delete_user(user)
        assert not self.service.user_exists(1)
```