Django Testing Patterns

pytest-django testing with factory_boy for fixture management.

Core Principles

1. pytest only - Never use Django's TestCase
2. factory_boy - Use factories for all test data
3. Mirror structure - Tests mirror app structure
4. Isolation - Each test fully isolated
5. Fast fixtures - Prefer @pytest.fixture over setUp

Installation

pip install pytest pytest-django factory-boy pytest-cov

Configuration

pytest.ini or pyproject.toml:

# pyproject.toml
[tool.pytest.ini_options]
DJANGO_SETTINGS_MODULE = "config.settings"
python_files = ["test_*.py", "*_test.py"]
python_classes = ["Test*"]
python_functions = ["test_*"]
addopts = [
    "--strict-markers",
    "-ra",
    "--tb=short",
]
markers = [
    "slow: marks tests as slow",
    "integration: marks tests as integration tests",
]

Test Structure

tests/
├── conftest.py              # Shared fixtures
├── factories/
│   ├── __init__.py
│   ├── user.py              # UserFactory
│   ├── product.py           # ProductFactory
│   └── order.py             # OrderFactory
├── unit/
│   ├── models/
│   │   ├── test_user.py
│   │   └── test_product.py
│   └── services/
│       └── test_user_service.py
├── integration/
│   └── api/
│       ├── test_users.py
│       └── test_products.py
└── e2e/
    └── test_checkout.py

Conftest Setup

tests/conftest.py:

import pytest
from django.test import Client
from ninja.testing import TestClient

from apps.myapp.api import api


@pytest.fixture
def client():
    """Django test client."""
    return Client()


@pytest.fixture
def api_client():
    """Django Ninja test client."""
    return TestClient(api)


@pytest.fixture
def authenticated_client(api_client, user):
    """API client with authentication."""
    api_client.headers["Authorization"] = f"Bearer {user.get_token()}"
    return api_client


@pytest.fixture
def user(user_factory):
    """Default test user."""
    return user_factory()


@pytest.fixture
def admin_user(user_factory):
    """Admin test user."""
    return user_factory(is_staff=True, is_superuser=True)

Factory Pattern

Base factory in factories/__init__.py:

import factory
from factory.django import DjangoModelFactory


class BaseFactory(DjangoModelFactory):
    """Base factory with common patterns."""

    class Meta:
        abstract = True

    @classmethod
    def _create(cls, model_class, *args, **kwargs):
        """Override to handle soft-deleted models."""
        obj = super()._create(model_class, *args, **kwargs)
        return obj

User factory in factories/user.py:

import factory
from factory import fuzzy
from apps.users.models import User
from . import BaseFactory


class UserFactory(BaseFactory):
    """Factory for User model."""

    class Meta:
        model = User
        skip_postgeneration_save = True

    email = factory.LazyAttribute(
        lambda obj: f"{obj.name.lower().replace(' ', '.')}@example.com"
    )
    name = factory.Faker("name")
    is_active = True

    @factory.post_generation
    def password(obj, create, extracted, **kwargs):
        password = extracted or "testpass123"
        obj.set_password(password)
        if create:
            obj.save(update_fields=["password"])

    @classmethod
    def _create(cls, model_class, *args, **kwargs):
        """Create with explicit password handling."""
        password = kwargs.pop("password", None)
        user = super()._create(model_class, *args, **kwargs)
        if password:
            user.set_password(password)
            user.save(update_fields=["password"])
        return user

Order factory with relationships (factories/order.py):

import factory
from decimal import Decimal
from apps.orders.models import Order, OrderItem
from . import BaseFactory
from .user import UserFactory
from .product import ProductFactory


class OrderFactory(BaseFactory):
    """Factory for Order model."""

    class Meta:
        model = Order

    user = factory.SubFactory(UserFactory)
    status = "pending"
    total = factory.LazyAttribute(lambda obj: Decimal("0.00"))

    @factory.post_generation
    def items(obj, create, extracted, **kwargs):
        if not create:
            return

        if extracted:
            for item in extracted:
                OrderItemFactory(order=obj, **item)
        else:
            # Create 1-3 random items
            import random
            for _ in range(random.randint(1, 3)):
                OrderItemFactory(order=obj)

        # Update total
        obj.total = sum(item.subtotal for item in obj.items.all())
        obj.save(update_fields=["total"])


class OrderItemFactory(BaseFactory):
    """Factory for OrderItem model."""

    class Meta:
        model = OrderItem

    order = factory.SubFactory(OrderFactory)
    product = factory.SubFactory(ProductFactory)
    quantity = factory.fuzzy.FuzzyInteger(1, 5)
    unit_price = factory.LazyAttribute(lambda obj: obj.product.price)

Register Fixtures

In conftest.py:

from tests.factories.user import UserFactory
from tests.factories.product import ProductFactory
from tests.factories.order import OrderFactory


@pytest.fixture
def user_factory():
    return UserFactory


@pytest.fixture
def product_factory():
    return ProductFactory


@pytest.fixture
def order_factory():
    return OrderFactory

Test Patterns

Model Tests

# tests/unit/models/test_user.py
import pytest
from apps.users.models import User


@pytest.mark.django_db
class TestUserModel:
    def test_create_user(self, user_factory):
        user = user_factory(email="test@example.com", name="Test User")

        assert user.email == "test@example.com"
        assert user.name == "Test User"
        assert user.is_active is True
        assert user.id is not None

    def test_soft_delete(self, user_factory):
        user = user_factory()
        user.delete()

        assert user.is_deleted is True
        assert User.objects.filter(id=user.id).exists()

    def test_display_name(self, user_factory):
        user = user_factory(name="John Doe")
        assert user.display_name == "John Doe"

        user_no_name = user_factory(name="", email="jane@example.com")
        assert user_no_name.display_name == "jane"

Service Tests

# tests/unit/services/test_user_service.py
import pytest
from unittest.mock import patch, MagicMock
from apps.users.services import UserService


@pytest.mark.django_db
class TestUserService:
    def test_create_user(self, user_factory):
        user = UserService.create(
            email="new@example.com",
            name="New User",
            password="securepass123",
        )

        assert user.email == "new@example.com"
        assert user.check_password("securepass123")

    def test_create_user_duplicate_email(self, user_factory):
        user_factory(email="existing@example.com")

        with pytest.raises(ValueError, match="already registered"):
            UserService.create(
                email="existing@example.com",
                name="Another User",
                password="password123",
            )

    @patch("apps.users.services.email.send_welcome_email")
    def test_create_user_sends_email(self, mock_send, user_factory):
        user = UserService.create(
            email="new@example.com",
            name="New User",
            password="password123",
        )

        mock_send.assert_called_once_with(user)

API Tests

# tests/integration/api/test_users.py
import pytest


@pytest.mark.django_db
class TestUsersAPI:
    def test_list_users_requires_auth(self, api_client):
        response = api_client.get("/users/")
        assert response.status_code == 401

    def test_list_users(self, authenticated_client, user_factory):
        user_factory.create_batch(5)

        response = authenticated_client.get("/users/")

        assert response.status_code == 200
        data = response.json()
        assert len(data["items"]) >= 5

    def test_create_user(self, authenticated_client):
        response = authenticated_client.post("/users/", json={
            "email": "new@example.com",
            "name": "New User",
            "password": "securepass123",
        })

        assert response.status_code == 201
        assert response.json()["email"] == "new@example.com"

    def test_get_user(self, authenticated_client, user_factory):
        user = user_factory()

        response = authenticated_client.get(f"/users/{user.id}")

        assert response.status_code == 200
        assert response.json()["id"] == str(user.id)

    def test_get_user_not_found(self, authenticated_client):
        import uuid
        fake_id = uuid.uuid4()

        response = authenticated_client.get(f"/users/{fake_id}")

        assert response.status_code == 404

Fixtures

See references/fixtures.md for advanced fixture patterns including:

• Database transactions
• File uploads
• External service mocking
• Time freezing

Additional Resources

Reference Files

• references/fixtures.md - Advanced fixture patterns, mocking, parametrization

Related Skills

• django-dev - Core Django patterns
• django-dev-ninja - API patterns being tested