So this is ancient but seems true and quite significant to me.
Basically, you don’t need to do a ton of usability testing, you just really need to do at least “some”. Carefully watching a handful of novice users try and use your system will very quickly uncover the significant problems. Don’t let “usability testing” be a monolith and so time consuming that is too big to ever actually do. Small, targeted and heeded, thats the goal.
Usability Testing with 5 Users (Jakob Nielsen’s Alertbox)
Elaborate usability tests are a waste of resources. The best results come from testing no more than 5 users and running as many small tests as you can afford.