Test #4's description is a bit off. Numbers 1-3 say lowerCaseLetters should be {expected}, but #4 says lowerCaseLetters should be {input}. If you would liked to show the input in the test description, maybe have something like lowerCaseLetters({input}) should be {expected} Also, #4 is not very good as a random test. The input is a template filled with numbers and the output is fixed, which allows for hardcoding. True random tests would be the best, but if you must use template based tests, then thrown in some spaces or capitals rather than just having the alphabet with two digits between each letter.