Also, please provide a few sample test cases to the user instead of just using the default setup. Perhaps you could move the current "Test Cases" into the "Sample Test Cases" section?

Only 4 fixed assertions in the entire test suite is hardly full code coverage and is far from enough for preventing logically flawed and/or hardcoded solutions. The lack of code coverage in a Kata as an Issue is recognised as an official CW stance so you should either (1) add at least 16 more unique, distinct fixed assertions including edge cases or better still, (2) write 100+ random tests.