The most fundamental part of unit testing is constructing individual test cases. A test case answers a single question about the code it is testing.
Unit testing is about automation.
Each test case is an island. Given that, let's build our first test case. To write a test case, first subclass the TestCase class of the unittest module. This class provides many useful methods which you can use in your test case to test specific conditions. It includes the lowest ten numbers, the highest number, every number that translates to a single-character Roman numeral, and a random sampling of other valid numbers.