Will it work?

Sometimes you can only do so much to ensure a success of a system. You have established a good data contract. You mocked your services and tested some service calls from the server to client in a dev environment. When it is time to test with the real service, will it work? You don't know. Sometimes things happen and you need to deliver and can't push back on the delivery date. The team writing the other component slipped their deadline, you are now in a bad situation where you are essentially testing in the user acceptance phase. This sucks but all you can do is hope it works.