The following is a simple A/B test I created. This particular page contains the script, the test and some of the results in the table at the bottom. The objective was to see what users expected and preferred to have happen after clicking a file link from the content list view. ("Open Preview" was the eventual winner but it was pretty close.)
Interesting how different each user is and that it's hard to always predict what flows and patterns users will prefer. So while testing is a necessary and valuable way to learn about user expectations, and a good way to build empathy and uncover patterns, UX designers often need to make and trust their decisions in order to drive the product and the business forward.