While researching more on Test Driven Development for SharePoint I came across a cute code duel website. The basis of this website is to write valid C# code and have the PEX engine analyse the code, come up with suitable test values and then compare those against expected values. If your code matches the secret implementation which is providing the expected values, the PEX scan will complete without errors.
Although this site can provide hours of fun entertainment for bored coders ( I could not resist to solve one or the other puzzle myself to try it out) and feel good factor for coming up with clever and light solutions (resource constraints stop you from using the full object model) it can also serve a very different purpose:
Recruitment Assistance! Sit your next development candidate infront of two or three of those puzzles and let them solve them there and then. No need to come up with lots of scenarios. No need to test the solutions. Heck, no need to know anything about coding at all. Just let them solve it and confirm that the puzzles complete with a success note.
Record exactly which puzzle was atempted, and if a candidate gets stuck let them try out another one. The senior developer can always evaluate which ones were completed and which ones not at a later stage.