Advanced Topics in pytest

pytest is highly flexible, enabling advanced techniques for efficient testing workflows. This section covers combining parameterized tests with fixtures, advanced fixture usage, and integrating pytest with popular frameworks.

Parameterized Tests with Fixtures

Combining parameterized tests with fixtures enables dynamic and reusable test scenarios.

Example: Parameterized Tests with Fixtures

import pytest
 
# Fixture to provide a base number
@pytest.fixture
def base_number():
    return 10
 
# Parameterized test using fixture and parameters
@pytest.mark.parametrize("multiplier, expected", [(1, 10), (2, 20), (3, 30)])
def test_multiplication(base_number, multiplier, expected):
    result = base_number * multiplier
    assert result == expected

In this example:

The base_number fixture provides a common starting value.
The @pytest.mark.parametrize decorator dynamically tests with multiple multiplier and expected values.

Advanced Fixture Usage

Autouse Fixtures

Autouse fixtures are automatically applied to all tests within a scope, eliminating the need for explicit inclusion.

Example: Using Autouse Fixtures

import pytest
 
# Autouse fixture for setup
@pytest.fixture(autouse=True, scope="function")
def setup_environment():
    print("Setting up environment...")
    yield
    print("Tearing down environment...")
 
def test_example():
    print("Running test example.")
    assert True

In this example:

The setup_environment fixture automatically applies to each test within the function scope.
yield is used for setup and teardown logic.

Fixture Dependency

Fixtures can depend on other fixtures to create complex setups.

Example: Dependent Fixtures

import pytest
 
# Database fixture
@pytest.fixture
 
def db_connection():
    return "Database Connection"
 
# Fixture dependent on db_connection
@pytest.fixture
def db_cursor(db_connection):
    return f"Cursor using {db_connection}"
 
def test_db_cursor(db_cursor):
    assert db_cursor == "Cursor using Database Connection"

Integrating pytest with Frameworks

pytest seamlessly integrates with popular frameworks like Django and FastAPI for testing web applications.

Example: Using pytest with Django

Install pytest-django:
```
pip install pytest-django
```

Configure pytest for Django in pytest.ini:

[pytest]
DJANGO_SETTINGS_MODULE = myproject.settings

Write tests using Django models:

import pytest
from myapp.models import MyModel
 
@pytest.mark.django_db
def test_model_creation():
    obj = MyModel.objects.create(name="Test")
    assert obj.name == "Test"

Example: Using pytest with FastAPI

Install httpx for testing FastAPI:
```
pip install httpx
```

Write tests for FastAPI endpoints:

from fastapi import FastAPI
from fastapi.testclient import TestClient
 
app = FastAPI()
 
@app.get("/items/{item_id}")
def read_item(item_id: int):
    return {"item_id": item_id}
 
client = TestClient(app)
 
def test_read_item():
    response = client.get("/items/1")
    assert response.status_code == 200
    assert response.json() == {"item_id": 1}

By mastering these advanced pytest topics, you can optimize your testing workflows and seamlessly integrate pytest with larger systems. This flexibility empowers robust and efficient testing strategies across diverse projects.

Real World examples of pytest Debugging with pytest