if you're an innovator, "Would you use this" is a question you really want to answer. But you can't ask it in a usability test. Usability tests can evaluate comprehension and ease of use, but test respondents can't reliably predict their own future behaviour. If you base your strategic choices on experiments where you ask them to do that, you can cause serious damage to your company.
But using the JTBD change making forces, and the MAO model, you can start to explore the factors that influence people's actions systematically . You can find out *when* and *why* people will use your new product idea, which is enough to work out whether your product is on the right track.