The test suite needs to be updated since the function chirp is no longer available. Moreover, most solutions use chirp, which was not recommended at the problem description and would render them false. On the other hand, the problem description also needs to be updated, it is not clear what the function "rise smoothly like an aircraft taking off from ground" is . Anyway, the few solutions that don't use chirp use sin, which is probably the right way to go. However, looking at the documentation of chirp, one may find several different functions to achieve a possible result and none of them is sin.

For the moment, this has become a hacking problem, until the author fixes it.