What would you accept as proof that the entire concept was invalid?

Is there any single experiment or study that would show this? If not, how many - and what would they need to cover?

That test was the entire basis of the concept. If it can't be measured or proven in any way then it's just an idea, not an actual "thing". Unconscious bias doesn't have any supporting evidence but lives on because people don't get the message that it's based on junk science.

> That test was the entire basis of the concept

Simply untrue. Even Patrick Forscher, one of the authors of the IAT critique that has become such a popular anti-diversity talking point, doesn't deny that implicit bias is real. Questioning the accuracy of one measurement is not the same as "no supporting evidence" let alone "junk science" and your use of those phrases only betrays that you're trying to argue from a basis other than fact.