What! How can this be? Yes it’s true, after many hours testing and contacting several people at Microsoft I can confirm that TIA will not work with WCF. The WCF client side code works correctly however the WCF service server side code will not get picked up by TIA.
I got this response from a helpful source at Microsoft:-
in IIS scenarios, we use the proxy to help pair up a client's requests (with are tied to the executing test) with the code executing in the server even in the process of multiple clients testing the same machine. The design principle was to err on the side of under-reporting to avoid saying a piece of code impacted a test unless it was truly caused by the test and avoid pollution from other concurrent requests. To accomplish that we hook in to the requests coming into the IIS pipeline and check for the "dye" we inject in the http headers at the client with the proxy. If the request is missing the dye, we don't account for the data to avoid pollution. Only HTTP requests can inject dye. WCF requests, because they don't necessarily pass through the proxy or have headers to inject the dye into, do not. Therefore we drop the request data on the floor.
This behaviour is intentional.
Whoa!! This is a biggie for me. Next task is to try and get this feature requested in vNext!