Introduction to doctest Module

Python includes a really useful module in its standard library that is called doctest. The doctest module will look at our code and determine if we have any text that looks like an interactive Python session. Then doctest will execute those given strings for testing to verify that they work the way they are written.

According to the Python documentation, doctest has three primary uses:

• Checking that a module’s docstrings are up-to-date by verifying the examples in the docstrings execute correctly
• Do regression testing using the interactive examples in the text or
• Write tutorial documentation for our package or module. We can do this by adding lots of examples in our docstrings that show inputs and outputs.

Creating a simple addition function

Let’s create a simple addition function that we can use to demonstrate what we can do with doctest. Save the following code into a file named test.py: