We need testing tools and tools to debug the application.
Since you haven't given us any details about this application and what testing should cover (and instead started talking about tools directly) you may find it beneficial to move up a few levels and create yourself some overview and structure before you dive in to write the test plan (or worse, haphazardly test some stuff w/o any plan or structure).
I'd recommend checking out http://www.ideahamster.org,
now mirror for ISECOM: http://www.isecom.org
. Also see OSSTMM at http://www.osstmm.org
and one mirror of the PDF (current version 2.1 IIRC) outlining it all at http://www.isecom.ca/mirror/osstmm.en.2.1.zip
OTOH if you have a test plan, post it and I'll comment on it and suggest tools if I can.