All our programs must be well-designed, well-written, and reliable to perform their functions as intended. Testing is a critical element in software development, with the unit testing framework being the most common type. Unit tests focus on the program’s basic building blocks, such as functions and methods in the classes. Unit tests are often created simultaneously with the source code to be tested; in the Test-driven Development (TDD) approach, unit tests come before the actual program code. Ready-made libraries are available to help create and run unit tests. One of the most popular of these libraries in the Python environment is PyTest.