I did not understand that all function calls should be cached. The current project description sounds to me like the goal is to cache only the most recent unique function call, and replace it whenever the function is called with arguments different only from those most recently used.

This took me too long to unravel, in part because the test cases are obscured. This kata would be improved by specifying that all unique function calls should be cached indefinitely, so that results derived from arbitrary arguments will not require a new function call NO MATTER HOW MANY UNIQUE FUNCTION CALLS HAVE OCCURRED IN BETWEEN.

Cool kata though.

Your function doesn't return anything, it just console logs it. So it's failing all the tests that expect to get a string back.