Can you explain how you would set up unit tests for a FastAPI application?

To set up unit tests for a FastAPI application, you would first install pytest and requests libraries. Then, create a test file in your project directory named ‘test_main.py’. In this file, import the necessary modules including FastAPI’s TestClient, pytest, and your main app.

Next, instantiate the TestClient with your FastAPI application as an argument. This client will be used to simulate HTTP requests in your tests.

For each endpoint in your application, write a function that sends a request to it using the TestClient and checks the response. Use pytest’s assert statements to verify the status code, headers, and body of the response match what is expected.

Remember to isolate each test case by mocking external dependencies and resetting any changes made during the test. Pytest fixtures can help manage setup and teardown tasks.