Type definitions should start with a '{', expecting serialized type 'ErrorResponse', got string starting with: MOCK FOR URL NOT FOUND

Question

I'm writing a unit test with Xunit and Moq on a ServiceStack microservice.

I can get a unit test of a GET route to work with one class, but with a different class it refuses to work. I'm moq'ing the ServiceStack.JsonHttpClient.GET in this route:

public SampleResponse Get(SampleRequest request)
{
    var myServiceRequest = new SampleService.myRequest() { PrimaryId = request.PrimaryId };
    using (client = ClientFactory.CreateSampleService()) // client is extension of ServiceStack.JsonHttpClient
    {
        // This code runs on local but throws the exception with unit testing
        SampleService.myResponse myResponse = client.Get(myServiceRequest);
        ...
    }
}

And here is the test:

// Arrange
var myServiceRequest = new SampleService.myRequest { PrimaryId = 1234 };
var myServiceResponse = new SampleService.myResponse { ... };

 // assigning the request with the desired response
mockService.MockGet(myServiceRequest, myServiceResponse);

// Act
var request = new ServiceModel.SampleRequest { PrimaryId = 1234 };
 // This calls the above function and fails
var response = frontEndService.Get(request); 

// Assert
Assert.NotEmpty(response.Items);
Assert.Equal(3, response.Items.ANumber);

But I get this Exception and InnerException:

ServiceStack.WebException: 'Not Found'

Inner Exception

SerializationException: Type definitions should start with a '{', expecting serialized type 'ErrorResponse', got string starting with: MOCK FOR URL NOT FOUND

I did an almost identical setup for a simpler class and it works, but this class refuses to unit test correctly. It DOES run fine when ran locally.

Answer 1

This Exception occurs when the JSON doesn’t match the Type you’re trying to deserialize into.