FastAPI Unit Testing with Pytest Concepts

Learning objective: By the end of this lesson, students will be able to describe the purpose of the Python Pytest library and demonstrate how to set up a Pytest testing environment.

Testing FastAPI with pytest

Pytest is a widely used testing framework in Python that simplifies writing and running tests. When developing a FastAPI application, testing ensures that individual components work correctly before deploying to production.

With Pytest, you can write unit tests for your FastAPI application, automatically execute them, and get detailed feedback on test results.

Installing pytest and dependencies

To start using Pytest with FastAPI, install the necessary dependencies:

pipenv install --dev pytest starlette httpx

• pytest: The core testing framework.
• starlette: Provides essential components for FastAPI, including test utilities.
• httpx: A powerful HTTP client used to simulate API requests in tests.

This will add those packages under the [dev-packages] section in your Pipfile and install them for development use.

Running tests with pytest

After installing the dependencies, you can execute your tests with the following command:

pipenv run pytest

Pytest will automatically discover test files and execute them, displaying a summary of the results in your terminal.