Testing API Basics 🧪

Testing ensures your API works correctly. FastAPI makes it easy with the TestClient.

Setting Up Tests

Install pytest:

pip install pytest httpx

Create `test_main.py`:

from fastapi.testclient import TestClient
from main import app

client = TestClient(app)

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

Run tests:

pytest

Testing Endpoints

from fastapi.testclient import TestClient
from main import app

client = TestClient(app)

def test_get_item():
    response = client.get("/items/1")
    assert response.status_code == 200
    assert response.json()["id"] == 1

def test_create_item():
    response = client.post("/items", json={"name": "Test", "price": 10.0})
    assert response.status_code == 201
    assert response.json()["name"] == "Test"

Testing with Different Status Codes

def test_not_found():
    response = client.get("/items/999")
    assert response.status_code == 404

def test_bad_request():
    response = client.post("/items", json={"price": "invalid"})
    assert response.status_code == 422

Testing Request Body

def test_create_user():
    response = client.post("/users", json={
        "name": "John",
        "email": "john@example.com"
    })
    assert response.status_code == 201
    assert response.json()["name"] == "John"

Running Tests

# Run all tests
pytest

# Run specific file
pytest test_main.py

# Run with verbose output
pytest -v

# Run specific test
pytest test_main.py::test_read_root

🔑 Key Takeaways

• ✅ Use TestClient to test endpoints

• ✅ Check status codes

• ✅ Verify response data

• ✅ Test error cases

• ✅ Use pytest framework