Since you have the file opened in the editor within PyCharm, you will see multiple green arrows to the left of your code, as illustrated here:
Run arrows in PyCharm
You might remember from Chapter 2, Installing and Configuring PyCharm, that by using a similar green arrow located at the beginning of the main scope of a Python program (the if __name__ == '__main__' condition), we can run the whole program. In general, these green arrows are indeed used to run, not just whole Python programs, but also code snippets and, in this case, unit tests. I personally like to call them run arrows.
As you click on any of these run arrows, ...
