With the increasing use of mobile apps and web-based applications, usability is becoming more and more important. Bad usability can lead to the rejection of an application and damage the image of organizations. This tutorial will give you a full overview of what usability testing is about and how you can approach this important testing aspect successfully. It describes the various aspects to consider: usability, user experience and accessibility. After that we cover commonly used standards and how to the use different approaches in evaluating usability. You will appreciate what is different when testing usability compared to functional testing and significantly raise your awareness. The tutorial is presented in an uncomplicated way with examples.