Test Driven Development has 3 simple rules:
- You are not allowed to write any production code unless it is to make a failing unit test pass.
- You are not allowed to write any more of a unit test than is sufficient to fail and compilation failures are failures.
- You are not allowed to write any more production code than is sufficient to pass the one failing unit test.
Source: http://butunclebob.com/ArticleS.UncleBob.TheThreeRulesOfTdd
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