Testing is good, and as developers we should all do more of it. Test-Driven Development (TDD) is a principle and a development discipline that can help immensely to improve the quality of your finished code. But because TDD relies on a rapid development cycle that requires frequently rebuilding, re-deploying and re-running tests, it requires that your tests are able to deploy and run quickly in order to be feasible. If they are not, then the developer will naturally tend to become less disciplined in running the tests regularly and the benefits of TDD will be diminished.
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