Usability Testing.

Usability testing is the best way to understand how real users experience your website or application. Unlike interviews or focus groups that attempt to get users to accurately self-report their own behavior or preferences, a well-designed user test measures actual performance on mission-critical tasks.

Myth #22: Usability testing is expensiveUX Myths
How to Conduct Usability StudiesNielsen Norman Group
Usability TestingUsability First
Running a Usability
The Art of Guerrilla Usability TestingUX BoothJuly 25th, 2017
Turn User Goals into Task Scenarios for Usability TestingNielsen Norman GroupJanuary 12th, 2014