As the title implies, I am looking for a good, simple, single word antonym of "assume". Alternatively, if no good antonym exists that satisfies the requirements below, I am also open to suggestions for a synonym of "assume" and its antonym.

The specific context is as a function name in a programming language, where the user can, for instance, assume X is zero. The antonym must follow the same pattern, i. e., _ X is zero and ideally be an "obvious" partner, i. e., when reading it should be clear to most people that it undoes the assumption.

I looked in a thesaurus, and the only good candidate I could find was "forget". The problem with this word is that I don't think it is immediately clear that it undoes an assumption, and I would struggle to remember it (ironically). Another word that I have considered is, "unassume". It is not in any dictionary, but I think it is fairly obvious from the context what it means, and I find it memorable.