Revolt of the Test Scripts

If testers are not invited early enough, they will not have the chance and the time to determine whether or not they have to adapt their existing scripts. As a matter of fact, some scripts will have to be de-activated since they start to report errors that aren't any. Someone smart once called this "False negatives", consequently the opposite exists, too (false positives). see also the blog entry as of July 2009 (The Test Successfully Failed).

...by the way, Test Tools and/or your own test scripts can be buggy, too (here a false negative).