[avgcorrection]

You use the naive implementation as a test oracle, limit `n` to something small (through the property tester), and use the test oracle on your efficient implementation.

Unit testing elegant functions has no value.

(fib is often used as an example. But you asked how to test it.)

[davidgrenier]

In combinatorics the adjusted fibonacci numbers start with 1 instead and is more commonly used as it aligns with many other results. One might want to document in the code, via a test, which sequence is of interest.

This is just an example of course but elegant functions might need to be tested.