The golden rules of Test-Driven Development (TDD) are:
- Don’t write source code until a test requires it
- Reference new classes, methods, variables etc in your test first, so the code won’t compile, and then fix it by declaring them
- Aim to have just one thing broken at a time if possible
Source: TDD, Jason Gorman, http://www.codemanship.co.uk/tdd.html