Enterprise software needs tests the way buildings need fire and safety inspections. If you know certain electrical conditions or structural issues could lead to catastrophe, you look for them not just once but again and again. Likewise, if you want to guard against certain problems or conditions in your software application, writing tests for them ensures that they won’t ever escape into production.
Tests are doubly important with dynamic languages like Python. With dynamic languages, whole classes of errors surface only at runtime. Robust test suites can help smoke out those problems, and provide a way for whomever inherits the codebase to do the same.
By default, Python comes with its own unit-testing framework, and it is both useful and widely used. But many other options exist, each with its own philosophy about how to build and maintain unit tests. Following is a rundown of the default, unittest, along with the three most significant alternatives.