Command Feedback doesn't work with @e and no mobs which match the selector

Usually, when you run a command, you get either the message: Killed ...
or something like: This specific player doesn't exist

But when you run a command and no entity fulfills the criterias, there won't be a error message (neither in command block nor chat).

Example:

/testfor @e[score_TEST=0]

No objective called TEST may exist