Pytest Overview

Pytest is a powerful and flexible testing framework for Python. It’s designed to make writing tests enjoyable and efficient. In this section, we’ll explore the basics of Pytest and how to use it to test your FastAPI applications.

Getting Started with Pytest

Installation: If you haven’t already, install Pytest using pip:Bashpip install pytest
Creating Test Files: Create a tests directory in your project and create test files within it. Pytest automatically discovers test files that follow the naming convention test*.py.
Writing Tests: Write your tests using the pytest.mark decorator to indicate test functions. Here’s a basic example:Pythonimport pytest def test_add(): assert 2 + 2 == 4

Running Tests

To run your tests, open a terminal and navigate to your project directory. Then, execute the following command:

Bash

pytest

Pytest will automatically discover and run all tests in your project.

Common Test Fixtures

Pytest provides built-in fixtures that can be used to set up and tear down test environments. Some common fixtures include:

tmpdir: Creates a temporary directory for testing.
monkeypatch: Allows you to patch functions or modules during tests.
requests_mock: Simulates HTTP requests for testing APIs.

Example using tmpdir:

Python

import pytest

def test_create_file(tmpdir):
    file_path = tmpdir.join("test.txt")
    with open(file_path, "w") as f:
        f.write("Hello, world!")
    assert file_path.exists()

Testing FastAPI Applications

To test FastAPI applications, you can use the fastapi.testclient.TestClient class to create a test client. This client allows you to make requests to your application and inspect the responses.

Example:

Python

from fastapi import FastAPI
import pytest

app = FastAPI()

@app.get("/")
def read_root():
    return {"Hello": "World"}

@pytest.fixture
def client():
    with TestClient(app) as client:
        yield client

def test_read_root(client):
    response = client.get("/")
    assert response.status_code == 200
    assert response.json() == {"Hello": "World"}