You need random testing. Good random testing. Not just tests that always expect true, not just integers, a true mixed bag.

You need edge cases. Numbers of the form 1e3 shouldn't have been an edge case, but by ignoring them initially, you made them an edge case. Testing with 0 is conspicuously lacking as well; people are even commenting on their own solution about that. Random tests can help you find more edge cases; you then add fixed tests for these. ( Ideally, when people submit a solution that occasionally fails a random test, they will report what value or what kind of value is an edge case to them, and you can add fixed testing for it. )

"Math.PI" might be an interesting edge case. :P

You need better failure messages, or test headers that include the tested value.

There are no test messages whatsoever. This makes it very difficult to figure out why a given test is failing. For this kata, most of them are just running the function with a value... but there's one near the end that isn't. So it just says "Expected: false, instead got: true", which gives me no idea of how to fix the problem.

I will try and make it a bit more specific. Thanks fore the feedback!

Thanks for the feedback I'll try and fix this "1e3", other than that did you find anything else thats a bug or are you just suggesting more test cases?

The instruction for this kata are vague. What is and isn't being considered a number?