I love what Norvig said. I can relate to it. As far as data structures are concerned, I think it's worth playing smart with your tests - focus on the "invariants" and ensure their integrity.

A classic example of invariant I can think of is the min-heap - node N is less than or equal to the value of its children - the heap property.

Five years from now, you might forget the operations and the nuanced design principles, but the invariants might stay well in your memory.