The reason is that the purpose of the test is to check that ```colorize``` won't raise any exception and not that it returns a specific value.
I was looking for an ```assertNoException``` but such a thing doesn't exist afaik.
Still, testing the return of the colorize function would be a nice thing but shouldn't it be done in another test.
Didn't bother to look if it already exists btw.
I can change it to ```assertEqual``` if you find it more robust / adequate.