Mock and Dependency Redundancy

[Fabian918]

Is your feature request related to a problem? Please describe.

We recently stumbled over the issue of testing specific scenarios with the gRPC Channel object.
The issue was simplified (without the project overhead).

Example issue:

public class CustomGrpcService
{
   public CustomGrpcService()
   {
      this.GrpcChannel = GrpcChannel.ForAddress("testUri");
   }

   public GrpcChannel GrpcChannel { get; set; }

   public void DoSomething()
   {
      if (this.GrpcChannel.State == ConnectivityState.Idle)
      {
         // Do Smth
      }
      else if (this.GrpcChannel.State == ConnectivityState.Ready)
      {
         // Do Smth
      }
      else if (this.GrpcChannel.State == ConnectivityState.Connecting)
      {
         // Do Smth
      }
      else if (this.GrpcChannel.State == ConnectivityState.TransientFailure)
      {
         // Do Smth
      }
      else if (this.GrpcChannel.State == ConnectivityState.Shutdown)
      {
         // Do Smth
      }
   }
}

Example tests:

[Fact]
   public void TestIdleBehaiour()
   {
      CustomGrpcService customGrpcService = new CustomGrpcService();
      customGrpcService.DoSomething();

      // Assert result in some way
   }

   [Fact]
   public void TestReadyBehaiour()
   {
      CustomGrpcService customGrpcService = new CustomGrpcService();
      customGrpcService.DoSomething();

      // Assert result in some way
   }
....

As of now, we have no possibility to change the behavior of the channel. Also, we would like to test this kind of functionality without acquiring a real OS port.
Mocking is unfortunately not an option, due to the class GrpcChannel being sealed.

Describe the solution you'd like

I would like a possibility to abstract the GrpcChannel object in some way.

Define interface to decouple functionallity from implementation

  public interface IGrpcChannel: IDisposable
   {
      public ConnectivityState State { get; }
      public Task ConnectAsync(CancellationToken cancellationToken = default);
      ....
   }

Open up sealed class

Remove the sealed keyword from the 'GrpcChannel' to allow a mock implementation.

Additional context

I believe that some applications could really benefit from this functionality. If it fits into the current project architecture, I would be glad to contribute.

Best
Fabian