Introduction to Pytest for Python Testing

Pytest introduction

Pytest is a framework for testing Python code. Pytest allows you to test your functions, methods, and classes with a straight forward syntax. In this tutorial, I’ll go over how to write tests for an async Python application.

Prerequisites

Before you start, make sure you have the following installed on your machine:

- Python 3.7 or greater

- Pytest

You can install Pytest using pip:

pip install pytest

Writing tests

In Pytest, tests are written as functions, methods, or classes. The syntax is very similar to writing your application code. To mark an async function, you need to decorate the function with the @pytest.mark.asyncio decorator.

import pytest

@pytest.mark.asyncio
async def test_function():
  assert 1 == 1

To write a test method, you need to define it inside a class and decorate it with @pytest.mark.asyncio.

import pytest

class TestClass:
    @pytest.mark.asyncio
    async def test_method(self):
        assert 1 == 1

Run pytests

To run your tests, use pytest from the command line. Pytest searches for tests files that are either prefixed with test_ or the suffix as *_test.py and pytest will execute the function, method, or class inside these files.

For example, to run all the tests in the current directory, you can use the following command:

pytest .

To run a specific test file, you can pass the file name as an argument to pytest.

pytest test_my_file.py

To run a specific test function, method, or class, you can use the -k option and specify a keyword to filter the tests by.

pytest -k test_my_function