You can ask them to do a coding task. If you want to send a coding task and they’re too elitist to do it, that should probably say something about the type of person they also are. Some give their candidates long assignments to make sure the candidate really wants the job and is willing to put in the effort.
You can also ask them for past code samples you can reference or a very clear track record of building an app from the ground up. There are also some recruiting sources like TripleByte who will do additional screening before the candidate gets to you. Doing some kind of coding test is important because the worst case scenario is hiring somebody who isn't even sure how to do the job on day one.
There are also sites like HackerRank that has short coding tests.