django-tdd

Django-Testen mit TDD

Testgetriebene Entwicklung für Django-Anwendungen mit pytest, factory_boy und Django REST Framework.

Wann aktivieren

• Schreiben neuer Django-Anwendungen
• Implementieren von Django REST Framework APIs
• Testen von Django-Modellen, Views und Serialsierern
• Einrichten der Test-Infrastruktur für Django-Projekte

TDD-Workflow für Django

Red-Green-Refactor-Zyklus

# Schritt 1: ROT - Fehlschlagenden Test schreiben
def 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

# Schritt 2: GRÜN - Test bestehen lassen
# User-Modell oder Factory erstellen

# Schritt 3: REFAKTORIEREN - Verbessern, während Tests grün bleiben

Einrichtung

pytest-Konfiguration

# 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: markiert Tests als langsam
    integration: markiert Tests als Integrationstests

Testeinstellungen

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

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

# Migrationen für Geschwindigkeit deaktivieren
class DisableMigrations:
    def __contains__(self, item):
        return True

    def __getitem__(self, item):
        return None

MIGRATION_MODULES = DisableMigrations()

# Schnelleres Passwort-Hashing
PASSWORD_HASHERS = [
    'django.contrib.auth.hashers.MD5PasswordHasher',
]

# E-Mail-Backend
EMAIL_BACKEND = 'django.core.mail.backends.console.EmailBackend'

# Celery immer 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):
    """Sicherstellung konsistenter Zeitzone."""
    settings.TIME_ZONE = 'UTC'

@pytest.fixture
def user(db):
    """Erstellen eines Testbenutzers."""
    return User.objects.create_user(
        email='[email protected]',
        password='testpass123',
        username='testuser'
    )

@pytest.fixture
def admin_user(db):
    """Erstellen eines Admin-Benutzers."""
    return User.objects.create_superuser(
        email='[email protected]',
        password='adminpass123',
        username='admin'
    )

@pytest.fixture
def authenticated_client(client, user):
    """Gibt authentifizierten Client zurück."""
    client.force_login(user)
    return client

@pytest.fixture
def api_client():
    """Gibt DRF API-Client zurück."""
    from rest_framework.test import APIClient
    return APIClient()

@pytest.fixture
def authenticated_api_client(api_client, user):
    """Gibt authentifizierten API-Client zurück."""
    api_client.force_authenticate(user=user)
    return api_client

Factory Boy

Factory-Einrichtung

# 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 für User-Modell."""

    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 für Category-Modell."""

    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 für Product-Modell."""

    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):
        """Tags zum Produkt hinzufügen."""
        if not create:
            return
        if extracted:
            for tag in extracted:
                self.tags.add(tag)

Verwendung von Factories

# tests/test_models.py
import pytest
from tests.factories import ProductFactory, UserFactory

def test_product_creation():
    """Test der Produkterstellung mit 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 des Produkts mit Tags."""
    tags = [TagFactory(name='electronics'), TagFactory(name='new')]
    product = ProductFactory(tags=tags)
    assert product.tags.count() == 2

def test_multiple_products():
    """Test der Erstellung mehrerer Produkte."""
    products = ProductFactory.create_batch(10)
    assert len(products) == 10

Modell-Tests

Modelltests

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

class TestUserModel:
    """Test User-Modell."""

    def test_create_user(self, db):
        """Test der Erstellung eines regulären Benutzers."""
        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 der Erstellung eines Superusers."""
        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 der String-Repräsentation des Benutzers."""
        user = UserFactory(email='[email protected]')
        assert str(user) == '[email protected]'

class TestProductModel:
    """Test Product-Modell."""

    def test_product_creation(self, db):
        """Test der Erstellung eines Produkts."""
        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 der automatischen Slug-Generierung."""
        product = ProductFactory(name='Test Product')
        assert product.slug == 'test-product'

    def test_product_price_validation(self, db):
        """Test, dass Preis nicht negativ sein kann."""
        product = ProductFactory(price=-10)
        with pytest.raises(ValidationError):
            product.full_clean()

    def test_product_manager_active(self, db):
        """Test der aktiven Manager-Methode."""
        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 der Bestandsverwaltung."""
        product = ProductFactory(stock=10)
        product.reduce_stock(5)
        product.refresh_from_db()
        assert product.stock == 5

        with pytest.raises(ValueError):
            product.reduce_stock(10)  # Nicht genug Bestand

View-Tests

Django View-Tests

# tests/test_views.py
import pytest
from django.urls import reverse
from tests.factories import ProductFactory, UserFactory

class TestProductViews:
    """Test Produkt-Views."""

    def test_product_list(self, client, db):
        """Test der Produktliste-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 der Produktdetail-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, dass Produkterstellung Authentifizierung erfordert."""
        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 der Produkterstellung als authentifizierter Benutzer."""
        response = authenticated_client.get(reverse('products:create'))

        assert response.status_code == 200

    def test_product_create_post(self, authenticated_client, db, category):
        """Test der Erstellung eines Produkts per 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-Tests

Serializer-Tests

# tests/test_serializers.py
import pytest
from rest_framework.exceptions import ValidationError
from apps.products.serializers import ProductSerializer
from tests.factories import ProductFactory

class TestProductSerializer:
    """Test ProductSerializer."""

    def test_serialize_product(self, db):
        """Test des Serialisierens eines Produkts."""
        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 des Deserialisierens von Produktdaten."""
        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 der Preisvalidierung."""
        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, dass Bestand nicht negativ sein kann."""
        data = {
            'name': 'Test Product',
            'price': '99.99',
            'stock': -5,
        }

        serializer = ProductSerializer(data=data)

        assert not serializer.is_valid()
        assert 'stock' in serializer.errors

API-ViewSet-Tests

# tests/test_api.py
import pytest
from rest_framework.test import APIClient
from rest_framework import status
from django.urls import reverse
from tests.factories import ProductFactory, UserFactory

class TestProductAPI:
    """Test Product-API-Endpunkte."""

    @pytest.fixture
    def api_client(self):
        """Gibt API-Client zurück."""
        return APIClient()

    def test_list_products(self, api_client, db):
        """Test der Auflistung von Produkten."""
        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 des Abrufens eines Produkts."""
        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 der Produkterstellung ohne Authentifizierung."""
        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 der Produkterstellung als authentifizierter Benutzer."""
        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 der Aktualisierung eines Produkts."""
        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 der Löschung eines Produkts."""
        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
        assert not Product.objects.filter(id=product.id).exists()

    def test_unauthorized_delete(self, unauthorized_api_client, db):
        """Test der Löschung ohne Authentifizierung."""
        product = ProductFactory()

        url = reverse('api:product-detail', kwargs={'pk': product.id})

        response = unauthorized_api_client.delete(url)

        assert response.status_code == status.HTTP_401_UNAUTHORIZED

Mocking

Patching und Side Effects

# tests/test_services.py
from unittest.mock import patch, Mock
import pytest
from django.core.mail import send_mail

class TestEmailService:
    """Test E-Mail-Dienst."""

    @patch('django.core.mail.send_mail')
    def test_send_welcome_email(self, mock_send_mail, db):
        """Test des Sendens einer Willkommens-E-Mail."""
        user = UserFactory()

        send_welcome_email(user)

        mock_send_mail.assert_called_once()
        args, kwargs = mock_send_mail.call_args
        assert 'Willkommen' in kwargs.get('subject', '')
        assert user.email in kwargs.get('recipient_list', [])

    @patch('django.core.mail.send_mail')
    def test_send_mail_failure(self, mock_send_mail, db):
        """Test der Fehlerbehandlung beim Senden einer E-Mail."""
        mock_send_mail.side_effect = Exception('SMTP-Fehler')
        user = UserFactory()

        with pytest.raises(Exception, match='SMTP-Fehler'):
            send_welcome_email(user)

Mocken von API-Aufrufen

# tests/test_external_api.py
from unittest.mock import patch
import pytest
import requests

class TestExternalAPI:
    """Test externe API-Integration."""

    @patch('requests.post')
    def test_payment_gateway(self, mock_post, db):
        """Test der Zahlungs-Gateway-Integration."""
        mock_response = Mock()
        mock_response.status_code = 200
        mock_response.json.return_value = {
            'status': 'erfolgreich',
            'transaction_id': 'txn_123'
        }
        mock_post.return_value = mock_response

        result = process_payment(100.00, 'tok_visa')

        assert result['status'] == 'erfolgreich'
        mock_post.assert_called_once()

Codeabdeckung

Coverage-Konfiguration

# .coveragerc
[run]
source = apps
omit =
    */migrations/*
    */tests/*
    */admin.py
    */apps.py
    */wsgi.py
    manage.py

[report]
exclude_lines =
    pragma: no cover
    def __repr__
    if self.debug:
    if settings.DEBUG
    raise AssertionError
    raise NotImplementedError
    if 0:
    if __name__ == .__main__.:

Zusammenfassung der Best Practices

1. Schreiben Sie zuerst den Test – Befolgen Sie den TDD-Rot-Grün-Refaktor-Zyklus
2. Verwenden Sie Factory Boy für saubere, wartbare Testdaten
3. Halten Sie Tests isoliert – Jeder Test sollte unabhängig ausführbar sein
4. Testen Sie Randfälle – Grenzwerte, Fehlerzustände und Berechtigungen
5. Mocken Sie externe Dienste – für zuverlässige, schnelle Tests
6. Streben Sie nach hoher Abdeckung – aber fokussieren Sie sich auf sinnvolle Tests
7. Verwenden Sie sprechende Testnamen – Dokumentieren Sie, was getestet wird
8. Halten Sie Testdaten minimal – Verwenden Sie nur das, was für den Test benötigt wird