Creating testable WCF service without OperationContext

Question

I've implemented a subscribe/publish (for my own enjoyment) WCF service which works reasonably well. Like all blogs and books I've seen they all use OperationContext to get the clients callback address. After a bit of reading, due to many people saying not to use OperationContext, I found myself not being able to create proper unit tests. Yet I haven't been able to find an alternative. I suppose the subscribe method could accept a parameter for it to provide its own address? I could see the code being testable from an intergration test stand point of view but not for unit testing since OperationContext would always be null.

How do I get the clients endpoint when they subscribe to my service without using OperationContext?

Little bit of an aside but where is a good WCF resource with testing in mind when showing code samples? There are tons of blogs out there reiterating the same code without providing sample test cases.

Thank you.

Answer 1

Microsoft developers really like sealed and static keywords (as well as internal) and they hate virtual. Because of that standard testing approaches and framworks often don't work. You have two choices:

1. Wrap access to OperationContext in custom class and inject an instance of the class to your service. This will involve additional work because you will need to do injection somewhere outside your service. For example constructor injection will need custom IInstanceProvider.
2. Use more poweful testing framework. Check Moles framework which is able to intercept calls and redirect them. This enables "mocking" sealed classes and static methods/properties.

Another approach is simply refactoring your code. Take away all business logic from your service into separate testable business class and let the service participate only in integration test. Service is more like infrastructure and not everything really needs unit test. Integration / end-to-end / behavior test is also test and valid approach.