While you're right, most people on here try to solve issues as consice, clever or creative :)

So I agree, it's not good practice, and one should never use code like this in production.

It's not the tests that are broken, it's your solution. Maybe you misunderstood the task.

I copied your code and ran it, here's the first bit of feedback:

Incorrect answer for n=195: expected 15 to equal 6

Your returned 15 is more than 1 digit long. You need to repeat this process until you get one-digit number (15 -> 1 + 5 -> 6)