I don't order "test dishes" as such, and certainly something I know I don't really want or like. If a Mexican, Tex-Mex or otherwise Latin restaurant cannot serve a decent salsa, which is the first thing you are usually offered, I am going to be out. A restaurant we used to go to frequently for a couple decades apparently changed hands, and now their salsa is just pureed tomato from a can. 
There is no onion, jalapeno or cilantro in the mix, and it is just really bad. Sure enough, the rest of the food has followed suit, and the scorching hot plates have been replaced with cheese enchiladas served with unmelted cheese. They used to have the best cheese enchiladas. 
They won't get my business anymore, but fortunately we have plenty of good Latin restaurants with better food in our area. I have to make my own cheese enchiladas now to get back to the quality of the now dead to me resto, but that's okay. I can get delicious and perfectly cooked, perfectly accompanied skirt steak at our current favorite place, so that eases the pain of the loss of an old friend restaurant where the staff all knew us. 
If a southern Indian restaurant can't serve a delicious paper masala dosa, I'm also out. I know from my attempts to make these at home how difficult they are and how involved, so I leave it to the professionals. Again, very fortunately we have a great southern Indian restaurant nearby and their dosas are still up to what inspired me to try making them at home. Wikipedia says:"Masala dosa was listed as number 49 on World's 50 most delicious foods compiled by CNN Go in 2011." I agree, and wish I could make them myself. They also have great fluffy and light idly, which is another good test for Southern Indian. I'm not even gonna attempt these at home.
