Django Testing with TDD

Contents

• When to Use
• TDD Workflow
• Testing Best Practices
• Coverage
• Quick Reference
• References

When to Use

• Writing new Django applications
• Implementing Django REST Framework APIs
• Testing Django models, views, and serializers
• Setting up testing infrastructure for Django projects

TDD Workflow

Red-Green-Refactor Cycle

RED     → Write failing test first
GREEN   → Write minimal code to pass
REFACTOR → Improve while keeping tests green
REPEAT  → Continue with next requirement

Example

# 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')

# Step 2: GREEN - Make test pass (implement User model)
# Step 3: REFACTOR - Improve while keeping tests green

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-db and --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

Running Coverage

# Run tests with coverage
pytest --cov=apps --cov-report=html --cov-report=term-missing

# Generate HTML report
open htmlcov/index.html

Coverage Targets

Quick Reference

Common Test Patterns

# Test with factory
def test_product_creation():
    product = ProductFactory(price=100.00)
    assert product.price == 100.00

def test_product_validation():
    product = ProductFactory.build(price=-1)
    with pytest.raises(ValidationError):
        product.full_clean()

def test_payment(mock_stripe, client, user):
    mock_stripe.Charge.create.return_value = {'status': 'succeeded'}
    # ... test payment flow

References

• Setup — pytest config, test settings, conftest
• Factory Examples — Factory Boy patterns
• Test Examples — Model, view, serializer, API tests
• Mocking & Integration — Mocking patterns and integration tests

Source: basidiocarp/lamella — distributed by TomeVault.