In this YouTube playlist, the Pencils of Rays problem from Project Euler is solved using TDD. The aim was strictly to show how a developer solves a problem. The videos are unedited so there are moments where I need to Google, etc. Please bear with me if you find the solution to be far from optimal in terms of performance, memory usage or any other important metric.
The code is stored in GitHub. The license is MIT so you can do whatever you want with this code.