Basically my question is what does the following line mean:
Context: Persons A and B are testing the combat abilities of one of two groups of people. To them unexpectedly person C arrives, with whom A and B have had mutual bad history (both sides did bad things). B reacts with surprise at the presence of C, but C behaves professionally and explains that she is there under orders and asks if there is a problem. Then the above line happens.
Now on to the line itself. I researched a bit, and there seems to be a possibility that が言うのもなんだけど is some sort of phrase. Allthough also after some time thinking about it, I can see it meaning:
That (is there a problem) is what we too meant/wanted to say/ask however,...
Which would make sense since they would want to know if the person means to start trouble. Which ties nicely into later B's comment to C about her not taking this chance to do revenge.
Then comes the later bit, which I assume has quite a bit of info that is supposed to be derived from context missing.
After some time looking at it, I think テストの相手があたしらで、might mean
because/since we are opponents in this test...
but I can't really tell what テストになんの？ means? I guess it might mean something along the line of A asking is this the test for her or something. But that is all contextual conjecture. In particular the になんの confuses me. I think it might be "に何の" but eh, I'm not 100% how that works then.