Azure-sdk-for-net: [FEATURE REQ] Make ServiceBusMessageBatch mockable

[drmathias]

Library or service name.
Azure.Messaging.ServiceBus

Is your feature request related to a problem? Please describe.
Currently there is no way to stub or mock ServiceBusMessageBatch, making it difficult to test batched calls.

[jsquire]

Thank you for your feedback. Tagging and routing to the team members best able to assist.

[JoshLove-msft]

@drmathias - thanks for raising this issue! Just to make sure I am understanding what you are looking to, are you simply looking to mock out a SendMessages call? Any chance you can include a snippet of the test code you are writing?

[drmathias]

I want to be able to test that the data being sent in a message batch is correct. Something like this. Although the return value of the call to CreateMessageBatchAsync(CancellationToken) cannot be mocked.

var clientName = "MyServiceBusClient";
var queueName = "MyServiceBusQueue";
var cancellationToken = new CancellationTokenSource().Token;

var serviceBusMessageBatchMock = new Mock<ServiceBusMessageBatch>();
var serviceBusSenderMock = new Mock<ServiceBusSender>();
serviceBusSenderMock.Setup(callTo => callTo.CreateMessageBatchAsync(cancellationToken))
                    .Returns(serviceBusMessageBatchMock.Object)
var serviceBusClientMock = new Mock<ServiceBusClient>();
serviceBusClientMock.Setup(callTo => callTo.CreateSender(It.IsAny<string>()))
                    .Returns(serviceBusSenderMock.Object);
var mockAzureClientFactoryMock = new Mock<IAzureClientFactory<ServiceBusClient>>();
mockAzureClientFactoryMock.Setup(callTo => callTo.CreateClient(clientName))
                          .Returns(serviceBusClientMock.Object);

var myMessageSender = new MyMessageSender(mockAzureClientFactoryMock.Object);

await myMessageSender.DoSomething(clientName, queueName, cancellationToken);

serviceBusMessageBatchMock.Verify(callTo => callTo.TryAddMessage(It.Is<ServiceBusMessage>(m => m.Body.ToBytes().IsEmpty)),
                                  Times.Exactly(100));
serviceBusSenderMock.Verify(callTo => callTo.SendMessagesAsync(serviceBusMessageBatchMock.Object, cancellationToken),
                            Times.Once);

[JoshLove-msft]

@drmathias, our general pattern here would be to make this output type (ServiceBusMessageBatch) creatable using a factory method as opposed to adding a protected constructor, which would make it mockable. You would still be able to create it for your tests, but would not be able to mock it.