Hi:
I have taken the C_TADMSEC_04 certification last november.
If you are working on Authorizations it wont be a problem at all.But, you need to go through ADM 940 , ADM 950,ADM 960 thoroughly.
But , you also need to go through ITS(Internet Transaction Server) .You will get around 8-11 question from this topic.
I too have searched for online tests but,couldn't find any.
I think you should just go through the material and give the test.
All the best.
Krishna.