Please inspect and approve!
Now most other solutions including author solution appends a : between minute and seconds:
This comment is hidden because it contains spoiler information about the solution
deleted (same message twice)
You can't accept my solution - that's funny, your kata and tests do:-)... and once again they do;-)...
So it's not a cheat, more a problem of your tests or kata. It was more a hint than a cheat:-)...
Sorry, I cannot accept your solution as valid.
If your intention was to make me to improve my test cases,
then I thank you for that otherwise it looks like a cheat solution to get tests passed.