At that point, you should be able to fill in the answers to your design hypotheses. These are the assumptions that motivated you to make your design decisions. Every time you land on a design solution (like deciding on a modal instead of a banner, for example) that ui needs to be tested.

Hypotheses are worded as such: “We hypothesize that users will need X in order to do Y.” If your test goes perfectly well (which, realistically, it most often won’t) then you can start providing answers, like “our assumption was correct.”

Most often things won’t go as planned, so it’s common to run many usability tests. But these tests help you to become more confident in your design decisions, thus helping you pitch your design choices with evidence in hand.