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

# Step 1: RED - Write failing test
def test_user_creation():
    user = User.objects.create_user(email='test@example.com', password='testpass123')
    assert user.email == 'test@example.com'
    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 green

Setup

pytest Configuration

# pytest.ini
[pytest]
DJANGO_SETTINGS_MODULE = config.settings.test
testpaths = tests
python_files = test_*.py
python_classes = Test*
python_functions = test_*
addopts =
    --reuse-db
    --nomigrations
    --cov=apps
    --cov-report=html
    --cov-report=term-missing
    --strict-markers
markers =
    slow: marks tests as slow
    integration: marks tests as integration tests

Test Settings

# config/settings/test.py
from .base import *

DEBUG = True
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': ':memory:',
    }
}

# Disable migrations for speed
class DisableMigrations:
    def __contains__(self, item):
        return True

    def __getitem__(self, item):
        return None

MIGRATION_MODULES = DisableMigrations()

# Faster password hashing
PASSWORD_HASHERS = [
    'django.contrib.auth.hashers.MD5PasswordHasher',
]

# Email backend
EMAIL_BACKEND = 'django.core.mail.backends.console.EmailBackend'

# Celery always eager
CELERY_TASK_ALWAYS_EAGER = True
CELERY_TASK_EAGER_PROPAGATES = True

conftest.py

# tests/conftest.py
import pytest
from django.utils import timezone
from 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.fixture
def user(db):
    """Create a test user."""
    return User.objects.create_user(
        email='test@example.com',
        password='testpass123',
        username='testuser'
    )

@pytest.fixture
def admin_user(db):
    """Create an admin user."""
    return User.objects.create_superuser(
        email='admin@example.com',
        password='adminpass123',
        username='admin'
    )

@pytest.fixture
def authenticated_client(client, user):
    """Return authenticated client."""
    client.force_login(user)
    return client

@pytest.fixture
def api_client():
    """Return DRF API client."""
    from rest_framework.test import APIClient
    return APIClient()

@pytest.fixture
def authenticated_api_client(api_client, user):
    """Return authenticated API client."""
    api_client.force_authenticate(user=user)
    return api_client

Factory Boy

Factory Setup

# tests/factories.py
import factory
from factory import fuzzy
from datetime import datetime, timedelta
from django.contrib.auth import get_user_model
from 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

# tests/test_models.py
import pytest
from 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) == 10

Model Testing

Model Tests

# tests/test_models.py
import pytest
from django.core.exceptions import ValidationError
from tests.factories import UserFactory, ProductFactory

class TestUserModel:
    """Test User model."""

    def test_create_user(self, db):
        """Test creating a regular user."""
        user = UserFactory(email='test@example.com')
        assert user.email == 'test@example.com'
        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='admin@example.com',
            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='test@example.com')
        assert str(user) == 'test@example.com'

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.red