We invest a lot of time and attention in order to achieve a good design, everyone is enthusiastic. Before the launch, of course, testing is done. No bugs? Great! Does the website run smoothly? Great! Does the website have everything our users need? We assume it has. A design was made with great attention to detail by experienced designers, so that must be a good enough. Right?
The method described here often occurs in practice. This can also lead to an acceptable result. But it is not without risk: the end user has not yet been able to find anything. And if there is one thing that practice always proves: no, you can not predict how your typical website visitor will behave. Do people have to think or search too much? Then they leave your site.
If you want your users to browse smoothly through your website, you have to put in the process as early as possible. The sooner, the better (and the cheaper). Please welcome ... the usability test!
Making assumptions: of course the designer makes assumptions. There is nothing inherently wrong with that. The essence of a usability test is to then to confirm or reject those assumptions. If the visitor can carry out the desired tasks on your website without having to think about it too much, then that's okay. It can be that simple.
Whether a usability test succeeds is determined by a number of factors that all have to be right: relevance, accessibility, effectiveness and experience.