Just keep the TDD life cycle, as follows, in mind:
A development to-do list helps organize and focus on tasks individually. It also helps provide a platform to list down ideas during the development process, which could be a single feature later on.
Let's add the first feature in the development to-do list--the add multiplication functionality:
3 * 3 = 9
The preceding list describes what needs to be done. It also provides a clear example of how to verify the multiplication 3 * 3 = ...