Any special case with 0% compression rate?

[amirabas-kz]

Hello,
Is there any special case, in which, this library can not compress the text? Thus, the compression rate would be 0%?

[Swiddis]

It generally does very poorly with highly repetitive strings

'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa' compressed by 0%