This is a known issue with the code runner which is not specific for this kata. I will mark your report as resolved, and there already are corresponding tickets on CW's Github.

For JS, there seems to be 100 small, 100 medium, and 250 large. So yes, it seems that the "exact amount of tests" in description is not that exact for JS.

how many large random tests are there? the description says 100 but i logged over 150 before timing out

Brilliant - both readable and clever.

There are 100 random tests...

I passed 10-13 random tests and then it times out, so it seems there are several random tests. One of the posts below says there are around 25 random tests, could be more. My code takes average 500ms to pass one random test, I believe I will have to pass each random test in less than 100ms to complete all tests.

how many random tests are there

Kata is still at Node 8.

why is Array.flat not a function?