An extension of type 'Microsoft.Activities.UnitTesting.Stubs.IMessagingStub' must be configured in order to run this workflow

Question

I have a workflow service and I need run unit test for workflow service

Here is code:

[TestClass]
public class WorkflowServiceTest
{
    private readonly Binding _binding = new NetNamedPipeBinding();
    private readonly EndpointAddress _serviceAddress = new EndpointAddress("net.pipe://localhost/WorkflowService");


    [TestMethod]
    [DeploymentItem(@"WorkflowServices\WorkflowService.xamlx")]
    public void StartWorkFlow()
    {
        #region Test 2
        var xamlInjector = new XamlInjector("WorkflowService.xamlx");
        xamlInjector.ReplaceAll
            (typeof(ExecutePofolioControllerActivityAsync), typeof(MockExecutePofolioControllerActivityAsync));
        xamlInjector.ReplaceAll
            (typeof (GetPortfolioControllerStatusActivity), typeof (MockGetPortfolioControllerStatusActivity));
        xamlInjector.ReplaceAll(typeof (GetTraderStatusesActivity), typeof (MockGetTraderStatusesActivity));
        xamlInjector.ReplaceAll(typeof(Delay),typeof(DelayStub));
        xamlInjector.ReplaceAll(typeof(Receive), typeof(ReceiveStub));
        xamlInjector.ReplaceAll(typeof(SendReply), typeof(SendReplyStub));

        // Then we load the service and replace the activities with mocks
        var mockedService = xamlInjector.GetWorkflowService();

        DelayStub.StubDuration = TimeSpan.FromSeconds(10);

        WorkflowServiceTestHost host = null;
        try
        {
            // Host the service
            using (host = WorkflowServiceTestHost.Open(mockedService, _serviceAddress))
            {
                // Setup a proxy to use named pipes
                var proxy = new WorkflowServiceClient(this._binding, this._serviceAddress);

                var serviceTask = new ServiceTask
                {
                    UserId = ValidId,
                    TaskType = TaskType.Start,
                    IssuerName = "UserTest",
                };

                proxy.Start(serviceTask);
            }
        }
        finally
        {
            if (host != null)
            {
                host.Tracking.Trace();
            }
        }

        #endregion

    }
}

So when I run debug UnitTest, I receive an error message at line "using (host = WorkflowServiceTestHost.Open(mockedService, _serviceAddress))":

Here is error:

"Test method StartWorkFlow threw exception: System.Activities.ValidationException: An extension of type 'Microsoft.Activities.UnitTesting.Stubs.IMessagingStub' must be configured in order to run this workflow."

I don't know why I receive that error.

Can someone show me the right code for it to work?