Well sorry, you might be right. But the getters/setters might be misleading for beginners who don't know how they are usually done in C# :)

In C#, the test is Assert.AreEqual(TimeFormat.GetReadableTime(359999),"99:59:59") (which matches the maximum value mentioned in the description), but it fails with:

String lengths are both 8. Strings differ at index 0.
Expected: "03:59:59"
But was: "99:59:59"

Moreover, on submit it fails with

Expected: "00:00:00"
But was: "24:00:00"

for input 86400. This is imho just not possible, for 86400 != 0. I think we got an issue here.

The instructions are unclear. I got caught in a ceiling fan.

To me, the kata seems to be perfectly fine (except that the Fibonacci Sequence does not start with 0).