We don't write tests only to cover bugs right?

This needs to be tested because values can be null, values cannot be returned and many other edge cases that this can fall into. The fact that this is an abstraction of a language behaviour introduced as part of our application means that we need to test this and ensure it works as in the language, so we don't have un-matched expectations of the users.

Relying on the assumption that "people are using incorrectly" isn't a good thing for many reasons that I don't need to express here.