Django Testing with TDD
Test-driven development for Django applications using pytest, factory_boy, and Django REST Framework.
When to Activate
- Writing new Django applications
- Implementing Django REST Framework APIs
- Testing Django models, views, and serializers
- Setting up testing infrastructure for Django projects
TDD Workflow for Django
Red-Green-Refactor Cycle
python
# Step 1: RED - Write failing testdef test_user_creation(): user = User.objects.create_user(email='[email protected]', password='testpass123') assert user.email == '[email protected]' assert user.check_password('testpass123') assert not user.is_staff
# Step 2: GREEN - Make test pass# Create User model or factory
# Step 3: REFACTOR - Improve while keeping tests greenSetup
pytest Configuration
ini
# pytest.ini[pytest]DJANGO_SETTINGS_MODULE = config.settings.testtestpaths = testspython_files = test_*.pypython_classes = Test*python_functions = test_*addopts = --reuse-db --nomigrations --cov=apps --cov-report=html --cov-report=term-missing --strict-markersmarkers = slow: marks tests as slow integration: marks tests as integration testsTest Settings
python
# config/settings/test.pyfrom .base import *
DEBUG = TrueDATABASES = { 'default': { 'ENGINE': 'django.db.backends.sqlite3', 'NAME': ':memory:', }}
# Disable migrations for speedclass DisableMigrations: def __contains__(self, item): return True
def __getitem__(self, item): return None
MIGRATION_MODULES = DisableMigrations()
# Faster password hashingPASSWORD_HASHERS = [ 'django.contrib.auth.hashers.MD5PasswordHasher',]
# Email backendEMAIL_BACKEND = 'django.core.mail.backends.console.EmailBackend'
# Celery always eagerCELERY_TASK_ALWAYS_EAGER = TrueCELERY_TASK_EAGER_PROPAGATES = Trueconftest.py
python
# tests/conftest.pyimport pytestfrom django.utils import timezonefrom django.contrib.auth import get_user_model
User = get_user_model()
@pytest.fixture(autouse=True)def timezone_settings(settings): """Ensure consistent timezone.""" settings.TIME_ZONE = 'UTC'
@pytest.fixturedef user(db): """Create a test user.""" return User.objects.create_user( email='[email protected]', password='testpass123', username='testuser' )
@pytest.fixturedef admin_user(db): """Create an admin user.""" return User.objects.create_superuser( email='[email protected]', password='adminpass123', username='admin' )
@pytest.fixturedef authenticated_client(client, user): """Return authenticated client.""" client.force_login(user) return client
@pytest.fixturedef api_client(): """Return DRF API client.""" from rest_framework.test import APIClient return APIClient()
@pytest.fixturedef authenticated_api_client(api_client, user): """Return authenticated API client.""" api_client.force_authenticate(user=user) return api_clientFactory Boy
Factory Setup
python
# tests/factories.pyimport factoryfrom factory import fuzzyfrom datetime import datetime, timedeltafrom django.contrib.auth import get_user_modelfrom apps.products.models import Product, Category
User = get_user_model()
class UserFactory(factory.django.DjangoModelFactory): """Factory for User model."""
class Meta: model = User
email = factory.Sequence(lambda n: f"user{n}@example.com") username = factory.Sequence(lambda n: f"user{n}") password = factory.PostGenerationMethodCall('set_password', 'testpass123') first_name = factory.Faker('first_name') last_name = factory.Faker('last_name') is_active = True
class CategoryFactory(factory.django.DjangoModelFactory): """Factory for Category model."""
class Meta: model = Category
name = factory.Faker('word') slug = factory.LazyAttribute(lambda obj: obj.name.lower()) description = factory.Faker('text')
class ProductFactory(factory.django.DjangoModelFactory): """Factory for Product model."""
class Meta: model = Product
name = factory.Faker('sentence', nb_words=3) slug = factory.LazyAttribute(lambda obj: obj.name.lower().replace(' ', '-')) description = factory.Faker('text') price = fuzzy.FuzzyDecimal(10.00, 1000.00, 2) stock = fuzzy.FuzzyInteger(0, 100) is_active = True category = factory.SubFactory(CategoryFactory) created_by = factory.SubFactory(UserFactory)
@factory.post_generation def tags(self, create, extracted, **kwargs): """Add tags to product.""" if not create: return if extracted: for tag in extracted: self.tags.add(tag)Using Factories
python
# tests/test_models.pyimport pytestfrom tests.factories import ProductFactory, UserFactory
def test_product_creation(): """Test product creation using factory.""" product = ProductFactory(price=100.00, stock=50) assert product.price == 100.00 assert product.stock == 50 assert product.is_active is True
def test_product_with_tags(): """Test product with tags.""" tags = [TagFactory(name='electronics'), TagFactory(name='new')] product = ProductFactory(tags=tags) assert product.tags.count() == 2
def test_multiple_products(): """Test creating multiple products.""" products = ProductFactory.create_batch(10) assert len(products) == 10Model Testing
Model Tests
python
# tests/test_models.pyimport pytestfrom django.core.exceptions import ValidationErrorfrom tests.factories import UserFactory, ProductFactory
class TestUserModel: """Test User model."""
def test_create_user(self, db): """Test creating a regular user.""" user = UserFactory(email='[email protected]') assert user.email == '[email protected]' assert user.check_password('testpass123') assert not user.is_staff assert not user.is_superuser
def test_create_superuser(self, db): """Test creating a superuser.""" user = UserFactory( email='[email protected]', is_staff=True, is_superuser=True ) assert user.is_staff assert user.is_superuser
def test_user_str(self, db): """Test user string representation.""" user = UserFactory(email='[email protected]') assert str(user) == '[email protected]'
class TestProductModel: """Test Product model."""
def test_product_creation(self, db): """Test creating a product.""" product = ProductFactory() assert product.id is not None assert product.is_active is True assert product.created_at is not None
def test_product_slug_generation(self, db): """Test automatic slug generation.""" product = ProductFactory(name='Test Product') assert product.slug == 'test-product'
def test_product_price_validation(self, db): """Test price cannot be negative.""" product = ProductFactory(price=-10) with pytest.raises(ValidationError): product.full_clean()
def test_product_manager_active(self, db): """Test active manager method.""" ProductFactory.create_batch(5, is_active=True) ProductFactory.create_batch(3, is_active=False)
active_count = Product.objects.active().count() assert active_count == 5
def test_product_stock_management(self, db): """Test stock management.""" product = ProductFactory(stock=10) product.reduce_stock(5) product.refresh_from_db() assert product.stock == 5
with pytest.raises(ValueError): product.reduce_stock(10) # Not enough stockView Testing
Django View Testing
python
# tests/test_views.pyimport pytestfrom django.urls import reversefrom tests.factories import ProductFactory, UserFactory
class TestProductViews: """Test product views."""
def test_product_list(self, client, db): """Test product list view.""" ProductFactory.create_batch(10)
response = client.get(reverse('products:list'))
assert response.status_code == 200 assert len(response.context['products']) == 10
def test_product_detail(self, client, db): """Test product detail view.""" product = ProductFactory()
response = client.get(reverse('products:detail', kwargs={'slug': product.slug}))
assert response.status_code == 200 assert response.context['product'] == product
def test_product_create_requires_login(self, client, db): """Test product creation requires authentication.""" response = client.get(reverse('products:create'))
assert response.status_code == 302 assert response.url.startswith('/accounts/login/')
def test_product_create_authenticated(self, authenticated_client, db): """Test product creation as authenticated user.""" response = authenticated_client.get(reverse('products:create'))
assert response.status_code == 200
def test_product_create_post(self, authenticated_client, db, category): """Test creating a product via POST.""" data = { 'name': 'Test Product', 'description': 'A test product', 'price': '99.99', 'stock': 10, 'category': category.id, }
response = authenticated_client.post(reverse('products:create'), data)
assert response.status_code == 302 assert Product.objects.filter(name='Test Product').exists()DRF API Testing
Serializer Testing
python
# tests/test_serializers.pyimport pytestfrom rest_framework.exceptions import ValidationErrorfrom apps.products.serializers import ProductSerializerfrom tests.factories import ProductFactory
class TestProductSerializer: """Test ProductSerializer."""
def test_serialize_product(self, db): """Test serializing a product.""" product = ProductFactory() serializer = ProductSerializer(product)
data = serializer.data
assert data['id'] == product.id assert data['name'] == product.name assert data['price'] == str(product.price)
def test_deserialize_product(self, db): """Test deserializing product data.""" data = { 'name': 'Test Product', 'description': 'Test description', 'price': '99.99', 'stock': 10, 'category': 1, }
serializer = ProductSerializer(data=data)
assert serializer.is_valid() product = serializer.save()
assert product.name == 'Test Product' assert float(product.price) == 99.99
def test_price_validation(self, db): """Test price validation.""" data = { 'name': 'Test Product', 'price': '-10.00', 'stock': 10, }
serializer = ProductSerializer(data=data)
assert not serializer.is_valid() assert 'price' in serializer.errors
def test_stock_validation(self, db): """Test stock cannot be negative.""" data = { 'name': 'Test Product', 'price': '99.99', 'stock': -5, }
serializer = ProductSerializer(data=data)
assert not serializer.is_valid() assert 'stock' in serializer.errorsAPI ViewSet Testing
python
# tests/test_api.pyimport pytestfrom rest_framework.test import APIClientfrom rest_framework import statusfrom django.urls import reversefrom tests.factories import ProductFactory, UserFactory
class TestProductAPI: """Test Product API endpoints."""
@pytest.fixture def api_client(self): """Return API client.""" return APIClient()
def test_list_products(self, api_client, db): """Test listing products.""" ProductFactory.create_batch(10)
url = reverse('api:product-list') response = api_client.get(url)
assert response.status_code == status.HTTP_200_OK assert response.data['count'] == 10
def test_retrieve_product(self, api_client, db): """Test retrieving a product.""" product = ProductFactory()
url = reverse('api:product-detail', kwargs={'pk': product.id}) response = api_client.get(url)
assert response.status_code == status.HTTP_200_OK assert response.data['id'] == product.id
def test_create_product_unauthorized(self, api_client, db): """Test creating product without authentication.""" url = reverse('api:product-list') data = {'name': 'Test Product', 'price': '99.99'}
response = api_client.post(url, data)
assert response.status_code == status.HTTP_401_UNAUTHORIZED
def test_create_product_authorized(self, authenticated_api_client, db): """Test creating product as authenticated user.""" url = reverse('api:product-list') data = { 'name': 'Test Product', 'description': 'Test', 'price': '99.99', 'stock': 10, }
response = authenticated_api_client.post(url, data)
assert response.status_code == status.HTTP_201_CREATED assert response.data['name'] == 'Test Product'
def test_update_product(self, authenticated_api_client, db): """Test updating a product.""" product = ProductFactory(created_by=authenticated_api_client.user)
url = reverse('api:product-detail', kwargs={'pk': product.id}) data = {'name': 'Updated Product'}
response = authenticated_api_client.patch(url, data)
assert response.status_code == status.HTTP_200_OK assert response.data['name'] == 'Updated Product'
def test_delete_product(self, authenticated_api_client, db): """Test deleting a product.""" product = ProductFactory(created_by=authenticated_api_client.user)
url = reverse('api:product-detail', kwargs={'pk': product.id}) response = authenticated_api_client.delete(url)
assert response.status_code == status.HTTP_204_NO_CONTENT
def test_filter_products_by_price(self, api_client, db): """Test filtering products by price.""" ProductFactory(price=50) ProductFactory(price=150)
url = reverse('api:product-list') response = api_client.get(url, {'price_min': 100})
assert response.status_code == status.HTTP_200_OK assert response.data['count'] == 1
def test_search_products(self, api_client, db): """Test searching products.""" ProductFactory(name='Apple iPhone') ProductFactory(name='Samsung Galaxy')
url = reverse('api:product-list') response = api_client.get(url, {'search': 'Apple'})
assert response.status_code == status.HTTP_200_OK assert response.data['count'] == 1Mocking and Patching
Mocking External Services
python
# tests/test_views.pyfrom unittest.mock import patch, Mockimport pytest
class TestPaymentView: """Test payment view with mocked payment gateway."""
@patch('apps.payments.services.stripe') def test_successful_payment(self, mock_stripe, client, user, product): """Test successful payment with mocked Stripe.""" # Configure mock mock_stripe.Charge.create.return_value = { 'id': 'ch_123', 'status': 'succeeded', 'amount': 9999, }
client.force_login(user) response = client.post(reverse('payments:process'), { 'product_id': product.id, 'token': 'tok_visa', })
assert response.status_code == 302 mock_stripe.Charge.create.assert_called_once()
@patch('apps.payments.services.stripe') def test_failed_payment(self, mock_stripe, client, user, product): """Test failed payment.""" mock_stripe.Charge.create.side_effect = Exception('Card declined')
client.force_login(user) response = client.post(reverse('payments:process'), { 'product_id': product.id, 'token': 'tok_visa', })
assert response.status_code == 302 assert 'error' in response.urlMocking Email Sending
python
# tests/test_email.pyfrom django.core import mailfrom django.test import override_settings
@override_settings(EMAIL_BACKEND='django.core.mail.backends.locmem.EmailBackend')def test_order_confirmation_email(db, order): """Test order confirmation email.""" order.send_confirmation_email()
assert len(mail.outbox) == 1 assert order.user.email in mail.outbox[0].to assert 'Order Confirmation' in mail.outbox[0].subjectIntegration Testing
Full Flow Testing
python
# tests/test_integration.pyimport pytestfrom django.urls import reversefrom 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': '[email protected]', 'password': 'testpass123', 'password_confirm': 'testpass123', }) assert response.status_code == 302
# Step 2: Login response = client.post(reverse('users:login'), { 'email': '[email protected]', '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='[email protected]').exists()Testing Best Practices
DO
- Use factories: Instead of manual object creation
- One assertion per test: Keep tests focused
- Descriptive test names:
test_user_cannot_delete_others_post - Test edge cases: Empty inputs, None values, boundary conditions
- Mock external services: Don't depend on external APIs
- Use fixtures: Eliminate duplication
- Test permissions: Ensure authorization works
- Keep tests fast: Use
--reuse-dband--nomigrations
DON'T
- Don't test Django internals: Trust Django to work
- Don't test third-party code: Trust libraries to work
- Don't ignore failing tests: All tests must pass
- Don't make tests dependent: Tests should run in any order
- Don't over-mock: Mock only external dependencies
- Don't test private methods: Test public interface
- Don't use production database: Always use test database
Coverage
Coverage Configuration
bash
# Run tests with coveragepytest --cov=apps --cov-report=html --cov-report=term-missing
# Generate HTML reportopen htmlcov/index.htmlCoverage Goals
| Component | Target Coverage |
|---|---|
| Models | 90%+ |
| Serializers | 85%+ |
| Views | 80%+ |
| Services | 90%+ |
| Utilities | 80%+ |
| Overall | 80%+ |
Quick Reference
| Pattern | Usage |
|---|---|
@pytest.mark.django_db | Enable database access |
client | Django test client |
api_client | DRF API client |
factory.create_batch(n) | Create multiple objects |
patch('module.function') | Mock external dependencies |
override_settings | Temporarily change settings |
force_authenticate() | Bypass authentication in tests |
assertRedirects | Check for redirects |
assertTemplateUsed | Verify template usage |
mail.outbox | Check sent emails |
Remember: Tests are documentation. Good tests explain how your code should work. Keep them simple, readable, and maintainable.
