Usually the technician (who comes for installation) will demonstrate in front of you how to test the LCD TV, for example, they will show you screens of different colors, such as white, blue red, black, etc. in order for you to see whether there are "dead dots". So, if the technician does not do that, then you have to ask him to do so.
Besides, you must make sure or ask the shop whether the delivery man is also the technician who will do the installation & testing for you.