I think it depends on what type of software you are doing. If it is "just" a mobile project then you can pre-plan most of it. But I come from a more scientific background and most of the stuff I did back at university was pretty much impossible to plan because you did not actually know how you would solve your current problem. Usually you would try several approaches until you find the one that works. In such a situation tests are hard to use because they reduce your flexibility.
How do you verify that the lack of understanding of the form of the solution was due to the problem domain (scientific) and not your lack of exactness of confirmation and ability to see what is in the problem due to not actually knowing?
