When it comes to evaluating the usability of an interface, user testing is often considered unnecessary if an expert has already reviewed it. Since people rarely behave the way you expect, an expert can find major usability problems, but usability tests always reveal surprising issues.

Usability testing and expert reviews are both useful and tend to have different findings, therefore it’s usually recommended to combine the two in order to get the most comprehensive analysis of the interface.

https://uxmyths.com/post/3086989914/myth-30-if-you-are-expert-you-dont-need-to-test-your-des