TB's mochitest: WARNING Found 'firefox' running before starting test browser!

[ISHIKAWA,chiaki]

I test my patches locally and run mochitest locally on my linux PC.

I noticed that there is a warning message issued by mochitest framework
as follows.:

WARNING Found 'firefox' running before starting test browser!

Is there an ill-effect if firefox is running on the same X server where
I start to execute TB mochitest?
I hope not.

I think the warning is meant to be for "firefox" mochitest and not for
"thunderbird", and
"test browser" mentioned in the warning string is actually thunderburd
binary.

I just wanted to be sure.

TIA

Chiaki

PS: If the warning is meant for firfox and I am running firefox prior to
running mochitest for firefox, does mochitest kills itself to avoid
confusion of test result? I bet it would, but no sure.