An introduction to unit testing with pytest

As we mentioned in the introduction, writing unit tests is an essential task in software development to deliver high-quality software. To help us be productive and efficient, a lot of libraries exist that provide tools and shortcuts dedicated to testing. In the Python standard library, a module exists for unit testing called unittest. Even though it’s quite common in Python code bases, many Python developers tend to prefer pytest, which provides a more lightweight syntax and powerful tools for advanced use cases.

In the following examples, we’ll write a unit test for a function called add, both with unittest and pytest, so that you can see how they compare on a basic use case. First, we’ll install pytest:

(venv) $ pip install pytest

Now, let’s see our simple add function, which simply performs an addition:

chapter09_introduction.py

def add(a: int, b: int) -> int:    return a...