As terrible as this kata is, this test case seems to be correct as far as the requirements go: -800 is evenly divisible by 400, so it is should be treated as a leap year, and have 366 days.

I'm getting the below error, I've been testing it for quite a while and it doesn't look like its properly tested for negative numbers in JS.

Should work for random years: expected '-800 has 365 days' to equal '-800 has 366 days'