Enough with theory! Let's look into how classical TDD techniques are applied, to discover algorithm implementations by moving with baby steps and triangulating into a more generic implementation. This talk is fully based on live coding in Scala, but does not require any prior experience with the language. It covers the following techniques: baby steps, transformation priority premise, mutable vs. immutable code, and functional programming habits that may get in the way. It will end with an introduction to tail call optimization, and raise the question which code was more readable.