5 things to check with your tests

Unit tests should always check for these five scenarios:

1. When there is 0 (zero).
2. When there is 1.
3. When there are a few.
4. When there are many.
5. Oops (There’s an exception).

Autotest only recognizes .rb files

Minitest-autotest throws a LoadError exception if the file containing the functions to be tested doesn’t have the .rb extension.

Reference: Minitest-autotest source code.