Prerequisite tests problems

[Vladimir Prus]

Hello,
I've trying to specify a test called "history.empty_main" as prerequisite for 
"time.empty_main" and cannot. The list of possible to in prerequisite adding 
dialog includes only time* tests and when I try "history.empty_main" 
manually, it results in message

    KeyError: history.empty_main

in the console, and test is simply not run -- without no messages in the gui.

Is is possible to specify prerequisite tests from different directory, and 
how?

- Volodya