Some automated test suites are inherently badly written: automated UI tests, for example, when the UI is rapidly changing. "Tests should be written so they woul

Some automated test suites are inherently badly written: automated UI tests, for example, when the UI is rapidly changing. "Tests should be written so they would indicate breakage early and address unstable, complex, but highly used parts of program." Yes: if your UI is changing every two days your automated UI tests break every two days, with no knowledge gained! For library code I'd use TDD, though. UIs are more suited to human testing (though cost pushes towards automated testing once the UI is stable enough), APIs are more suited to automated testing. And if you're doing prototyping or usability testing you might not need either (you might not even need to write code, sometimes).