Why it matters: The way users navigate through your product has a direct influence on whether they will accomplish their goals there.
How to test it: Check your documentation on the site's information architecture. Make sure that proper navigation is present on every page, it doesn’t change or disappears in any place. Before diving into visual design, try 'card sorting' or 'tree testing' methods to ensure your information architecture pathways are as intuitive as possible. More on 'card sorting' method here:
Card sorting is a method used to help design or evaluate the information architecture of a site. In a card sorting session, participants organize topics into categories that make sense to them and they may also help you label these groups.
Check this article about ’tree testing’:
Tree Testing: Fast, Iterative Evaluation of Menu Labels and Categories
Overlapping information categories and confusing labels are two of the most pervasive problems in website design. Fortunately, there are fast and effective techniques you can use to create categories and labels that will make sense to your audience.