Mocking Azure RoleEnvironment API with Microsoft Fakes

Question

I'm trying to mock the Azure RoleEnvironment API with Microsoft Fakes. The problem is that I can't find a way to arrange the shims/stubs so that I can exercise the code in a unit test.

For instance, suppose I have the following code:

using Microsoft.WindowsAzure.ServiceRuntime;
// ...
Role role = RoleEnvironment.CurrentRoleInstance.Role;
int count = role.Instances.Count;

How would I mock the above with Fakes so that I can run it in a unit test?

So far my attempts fail because the RoleInstance class appears to have abstract properties with internal setters which prevents me from deriving a class from RoleInstance. This in turn prevents me from providing a shim for RoleEnvironment.CurrentRoleInstance.

BTW, I'm fully aware that relying too much on Fakes can be considered harmful. The thing is, I already have a wrapper for RoleEnvironment, together with production and test implementations. The code I'm trying to mock is in the production implementation which I want to test as well.

Answer 1

Unfortunately, I don't believe it is possible to isolate this code with Microsoft Fakes today. Normally, you would want to shim the RoleEnvironment.CurrentRoleInstance property to return a stub RoleInstance, that returns a stub Role. We can shim the CurrentRoleInstance property. But as you pointed out, both RoleInstance and Role are abstract classes with internal constructors, which we cannot stub with the current version of Fakes.