Skip to main content

​
Overview

The Python service uses pytest as the testing framework with SQLAlchemy database fixtures for test isolation. All tests run against a test database that is created fresh for each test function.

​
Pytest Configuration

​
Test Fixtures (conftest.py)

The tests/conftest.py file defines reusable fixtures: 
@pytest.fixture(scope="session")
def app():
    """Create application for testing."""
    app = create_app("testing")
    return app

@pytest.fixture(scope="function")
def db(app):
    """Create a fresh database for each test."""
    with app.app_context():
        _db.create_all()
        yield _db
        _db.session.rollback()
        _db.drop_all()

@pytest.fixture
def client(app, db):
    """Create a test client."""
    return app.test_client()

​
Available Fixtures

Application instance configured for testing environment.Scope: Session (created once per test session)
Fresh database instance with all tables created.Scope: Function (recreated for each test)Cleanup: Automatically rolls back and drops all tables after each test
Flask test client for making HTTP requests.Usage: client.get(), client.post(), etc.
Pre-created user with credentials:
List of 5 products across different categories:
  • Widget A ($29.99) - widgets category
  • Widget B ($49.99) - widgets category
  • Gadget X ($199.99) - gadgets category
  • Gadget Y ($299.99) - gadgets category
  • Tool Z ($15.99) - tools category
JWT access token for the sample user.Usage: Add to request headers:
headers={"Authorization": f"Bearer {auth_token}"}
5 pre-created orders with items for the sample user.

​
Test Files

​
test_auth.py - Authentication Tests

Tests for user registration and login endpoints. Example Test: 
class TestRegistration:
    def test_register_success(self, client):
        """Should register a new user successfully."""
        response = client.post(
            "/api/auth/register",
            data=json.dumps({
                "email": "[email protected]",
                "password": "securepassword123",
                "name": "New User",
            }),
            content_type="application/json",
        )
        assert response.status_code == 201
        data = response.get_json()
        assert data["user"]["email"] == "[email protected]"
        assert "access_token" in data
Coverage:
  • Successful registration with valid data
  • Missing required fields validation
  • Duplicate email prevention (409 conflict)
  • Successful login with valid credentials
  • Invalid password rejection (401 unauthorized)
  • Non-existent user handling

​
test_products.py - Product Tests

Tests for product listing, search, and creation. Example Test: 
class TestProductListing:
    def test_list_products_by_category(self, client, sample_products):
        """Should filter products by category."""
        response = client.get("/api/products/?category=widgets")
        assert response.status_code == 200
        data = response.get_json()
        assert len(data["products"]) == 2
Coverage:
  • Product listing with pagination
  • Category filtering
  • Search functionality
  • Product retrieval by ID
  • Product creation (requires authentication)
  • SQL injection prevention in search
  • 404 handling for non-existent products

​
test_orders.py - Order Tests

Tests for order creation and management. Example Test: 
class TestOrderCreation:
    def test_create_order_with_discount(self, client, auth_token, sample_products):
        """Should apply discount code to order."""
        response = client.post(
            "/api/orders/",
            data=json.dumps({
                "items": [
                    {"product_id": sample_products[2].id, "quantity": 1},
                ],
                "discount_code": "SAVE20",
            }),
            content_type="application/json",
            headers={"Authorization": f"Bearer {auth_token}"},
        )
        assert response.status_code == 201
        data = response.get_json()
        assert data["order"]["discount_amount"] == 40.0
Coverage:
  • Order creation with multiple items
  • Stock validation (insufficient stock handling)
  • Discount code application
  • Empty order rejection
  • Order listing for authenticated users
  • Single order retrieval
  • Non-existent product handling

​
test_payments.py - Payment Tests

Tests for payment calculation and checkout processing. Example Test: 
class TestTaxCalculation:
    def test_calculate_tax_standard_amount(self):
        """Should calculate 8.5% tax on $200.00."""
        tax = calculate_tax(200.00)
        assert tax == 17.0  # 200 * 0.085 = 17.0
Coverage:
  • Tax calculation at 8.5% rate
  • Percentage discount application (SAVE20 = 20% off)
  • Flat discount application (FLAT5 = $5 off)
  • Invalid discount code handling
  • Payment total calculation
  • Checkout flow completion
  • Order status update to “paid”

​
test_security.py - Security Tests

Tests for SQL injection prevention and security vulnerabilities. Example Test: 
class TestSQLInjection:
    def test_search_with_union_select(self, client, sample_products):
        """Should not be vulnerable to UNION-based SQL injection."""
        response = client.get(
            "/api/products/search?q=x' UNION SELECT 1,2,3,4,5,6--"
        )
        assert response.status_code == 200
        data = response.get_json()
        # Verify no injected data is returned
        for product in data.get("products", []):
            assert isinstance(product["name"], str)
            assert product["name"] != "2"  # Injected value
Coverage:
  • Single quote handling in search
  • UNION-based SQL injection prevention
  • Boolean-based SQL injection prevention
  • Input sanitization verification

​
Running Python Tests

1

Activate virtual environment

cd python-service
source venv/bin/activate
2

Run all tests

python -m pytest tests/ -v
Options:
  • -v: Verbose output with test names
  • --tb=short: Shorter traceback format
  • -k <pattern>: Run tests matching pattern
  • -x: Stop after first failure
3

Run specific test file

python -m pytest tests/test_auth.py -v
4

Run specific test class or function

# Run all tests in TestRegistration class
python -m pytest tests/test_auth.py::TestRegistration -v

# Run specific test function
python -m pytest tests/test_auth.py::TestRegistration::test_register_success -v

​
Test Output Example

========================= test session starts =========================
platform linux -- Python 3.11.0, pytest-7.4.0
rootdir: /path/to/python-service
collected 25 items

tests/test_auth.py::TestRegistration::test_register_success PASSED
tests/test_auth.py::TestRegistration::test_register_missing_fields PASSED
tests/test_auth.py::TestRegistration::test_register_duplicate_email PASSED
tests/test_auth.py::TestLogin::test_login_success PASSED
tests/test_auth.py::TestLogin::test_login_wrong_password PASSED

========================= 25 passed in 2.34s =========================

​
Best Practices

Each test should be independent and not rely on the state from other tests. The db fixture ensures database isolation.
Use descriptive test names that explain what the test verifies. Follow the pattern: test_<action>_<expected_result>
The test database is automatically created and destroyed for each test function, ensuring complete isolation.

Build docs developers (and LLMs) love

Get started for freeTalk to us