Mocking Azure ServiceBusClient dependency not working with AutoFixture.AutoMoq Freeze

Question

The following class has a dependency on ServiceBusClient from the Azure.Messaging.ServiceBus NuGet package (for sending Azure Service Bus messages):

public class MyService {
    private readonly ServiceBusClient _serviceBusClient;

    public MyService(ServiceBusClient serviceBusClient) {
        _serviceBusClient = serviceBusClient;
    }

    public async Task SendServiceBusMessageAsync() {
        var sender = _serviceBusClient.CreateSender("Topic_Name");
        // Send the message
    }
}

When mocking the ServiceBusClient dependency using Moq as follows, it works as desired, and the call to CreateSender returns what was specified in the setup:

    var mockServiceBusClient = new Mock<ServiceBusClient>();
    mockServiceBusClient.Setup(s => s.CreateSender(It.IsAny<string>())).Returns(new Mock<ServiceBusSender>().Object);

    var sut = new MyService(MockServiceBusClient.Object);
    await sut.SendServiceBusMessageAsync();

When attempting the same using AutoFixture.AutoMoq as shown below, the following error occurs: AutoFixture.ObjectCreationExceptionWithPath The connection string could not be parsed; either it was malformed or contains no well-known tokens.

    fixture = new Fixture();
    fixture.Customize(new AutoMoqCustomization());

    var mockServiceBusClient = fixture.Freeze<Mock<ServiceBusClient>>();
    mockServiceBusClient.Setup(s => s.CreateSender(It.IsAny<string>())).Returns(new Mock<ServiceBusSender>().Object);

    var sut = fixture.Create<MyService>();
    await sut.SendServiceBusMessageAsync();

Does anyone know how to get it to work with AutoFixture.AutoMoq?

I looked at ServiceBusClient, and I see that the parameterless constructor is protected, and the public constructor takes a connection string. I'm guessing AutoFixture.AutoMoq is using the latter, but as I understand it uses Moq. Why then does it work fine if done with Moq directly?

I think I'll just pull the method into another class and then inject and mock that, but it would be nice to understand why this is happening.

Answer 1

You could build one with OmitAutoProperties so it will not try to pass on a connection string:

var mockServiceBusClient = fixture.Build<Mock<ServiceBusClient>>().OmitAutoProperties().Create();
fixture.Inject(mockServiceBusClient);