Hi @flint.christensen, thanks for writing in!
Here's hopefully a clarification of the difference:
The Unit Test file should just contain the code for the function/method. This is the file the checker looks for when running the test cases and what students need to complete correctly to submit.
The Scratchpad file is just a file that runs a separate program (in whatever language you're using). There is no actual relationship between them. The scratchpad is just there so while you're working on solving the problem, you have a place to test out some code, print things out, and experiment to help solve the problem.
This can be especially helpful because the Unit Test file isn't really runnable, since it's not a full program. It's just the function/method that we want tested.
Hope this helps clarify. Any other questions about the Scratchpad or Unit Tests?