I'm with @lil_tea on this one, there is no clear-cut answer to this one. What you test should be driven by insight into objectives, users/audience and qualitative- and quantitative data (any source you see fit) - those tests are the ones that will drive improvement.
In most cases, patterns will form, and you will see where and what needs to be improved. Test major friction first, go ahead and fine tune later!
I'm with @lil_tea on this one, there is no clear-cut answer to this one. What you test should be driven by insight into objectives, users/audience and qualitative- and quantitative data (any source you see fit) - those tests are the ones that will drive improvement.
In most cases, patterns will form, and you will see where and what needs to be improved. Test major friction first, go ahead and fine tune later!