That easy?

UPD
See what you meant

As Voile said tests with more than 2 tail calls are not different from tests with 2 calls.

No sample tests.

This should really not be 5 kyu

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Nah forget it I'll change it myself later

Added

Well, I mean, adding that example is trivial, but why?

A change should happen for a reason, and you really haven't elaborated on what makes it more beneficial to add that specific test.

Fixed

Fixed

more examples should be added to infere wich of the two functions is called

I'll add this test.

I don't know, but what's the difference between that and naturalNumbers.tail().tail().head(), which is already in the sample tests?

Like, if for some reasons your code only breaks when more than 2 tail is called, then your code is something.

Please add an example for naturalNumbers.tail().tail().tail().tail().head()