## Integration Testing

### Full Flow Testing

```python
# tests/test_integration.py
import pytest
from django.urls import reverse
from tests.factories import UserFactory, ProductFactory

class TestCheckoutFlow:
    """Test complete checkout flow."""

    def test_guest_to_purchase_flow(self, client, db):
        """Test complete flow from guest to purchase."""
        # Step 1: Register
        response = client.post(reverse('users:register'), {
            'email': 'test@example.com',
            'password': 'testpass123',
            'password_confirm': 'testpass123',
        })
        assert response.status_code == 302

        # Step 2: Login
        response = client.post(reverse('users:login'), {
            'email': 'test@example.com',
            'password': 'testpass123',
        })
        assert response.status_code == 302

        # Step 3: Browse products
        product = ProductFactory(price=100)
        response = client.get(reverse('products:detail', kwargs={'slug': product.slug}))
        assert response.status_code == 200

        # Step 4: Add to cart
        response = client.post(reverse('cart:add'), {
            'product_id': product.id,
            'quantity': 1,
        })
        assert response.status_code == 302

        # Step 5: Checkout
        response = client.get(reverse('checkout:review'))
        assert response.status_code == 200
        assert product.name in response.content.decode()

        # Step 6: Complete purchase
        with patch('apps.checkout.services.process_payment') as mock_payment:
            mock_payment.return_value = True
            response = client.post(reverse('checkout:complete'))

        assert response.status_code == 302
        assert Order.objects.filter(user__email='test@example.com').exists()
```