tiangolo.fastapi

Thanks to Starlette's TestClient, testing FastAPI applications is easy and enjoyable.

It is based on Requests, so it's very familiar and intuitive.

With it, you can use pytest directly with FastAPI.

Using `TestClient`

Import TestClient from starlette.testclient.

Create a TestClient passing to it your FastAPI.

Create functions with a name that starts with test_ (this is standard pytest conventions).

Use the TestClient object the same way as you do with requests.

Write simple assert statements with the standard Python expressions that you need to check (again, standard pytest).

{!./src/app_testing/tutorial001.py!}

!!! tip Notice that the testing functions are normal def, not async def.

And the calls to the client are also normal calls, not using `await`.

This allows you to use `pytest` directly without complications.

In a real application, you probably would have your tests in a different file.

And your FastAPI application might also be composed of several files/modules, etc.

Let's say you have a file main.py with your FastAPI app:

{!./src/app_testing/main.py!}

Then you could have a file test_main.py with your tests, and import your app from the main module (main.py):

{!./src/app_testing/test_main.py!}

You can use the same TestClient to test WebSockets.

For this, you use the TestClient in a with statement, connecting to the WebSocket:

{!./src/app_testing/tutorial002.py!}

When you need your event handlers (startup and shutdown) to run in your tests, you can use the TestClient with a with statement:

{!./src/app_testing/tutorial003.py!}