I think we need to keep the following challenges in mind:
1) Unlike traditional apps (web development, rich client apps), there is no direct user interface to the services you are building and testing, so you need bring that up into an interface that allows you to interact with these services easily (i.e., provide data, construct messages, etc.)
2) Similar to traditional apps, there are functional requirements that your services need to adhere to, i.e., implement the requirements correctly and executes your use case scenarios correctly, but there are also non-functional quality aspects as well:
