When it’s an exercise, or a rehearsal, or a workshop. A subtle distinction maybe, but the word "test" can sometimes have undesirable connotations. It can suggest that the result will either be a pass or a fail, putting undue pressure on the participants, whereas the word "exercise" or "rehearsal" implies training and improvement.

Whilst a problem-free test may be seen by some as "successful", this can give a false sense of security. In fact, the most successful tests or exercises are the ones that flush out all the potential problems. This allows improvements to be made to plans, processes and procedures, thereby increasing the likelihood of recovery if it ever has to be done "in anger" (or in an emergency).

So, which would you rather have?