We design our code for performance, maintenance, simplicity, extensibility and other goals, but most of us do not think about testability as a design goal, yet verifying the correctness of our code is of great importance. What does it mean to have testable code, and what kind of trade offs does one have to think about when designing for testability. Turns out that testable code is well designed code, and it has many of the characteristics we search for such as low cohesion, separation of concerns, proper encapsulation and many others.
