Wrap-Up

When you look at the result, nobody would seriously consider to deliver this piece of software. Many more tests would follow along with their implementation. And heavy refactoring would be in all likelyhood part of the further work.

However, this tutorial covered several important principles of test-driven development using a simple calculator class and csUnit as the unit testing framework.

Always write your tests first.
A test consists of three major parts: a) set up required object(s), b) manipulate the object(s), and c) assert outcome.
Implement as little as possible, keep it as simple as possible, sometimes even simplistic.
Run your tests frequently.
Test only one bit of functionality at a time.