AutoFixture with AutoMoq always returns the same instance after Customization

Question

I have the following code to set up some response from a mock client (some parts of the code are omitted for brevity):

IFixture fixture = new Fixture().Customize(new AutoMoqCustomization() 
                   { ConfigureMembers = true, GenerateDelegates = true });

CustomNetworkCall<ResponseObject> GetNewResponse()
{
  var response = fixture.Create<ResponseObject>();
  fixture.Customize<ResponseObject>(ro => ro.FromFactory(() =>
  {
    response.DataList.AddRange(fixture.CreateMany<DataObject>(random.Next(3, 10)));
    return response;
  })
  .With(item => item.Id, Guid.NewGuid().ToString())  
  );
  return fixture.Create<CustomNetworkCall<ResponseObject>>();
}

//setup for mock code
clientMock.Setup(client => 
   client.GetResponseAsync(
       It.IsAny<IdDescription>(),
       It.IsAny<DataValidation>(), 
       It.IsAny<DateTime?>(), 
       It.IsAny<CancellationToken>()))
  .Returns(GetNewResponse());
           

I use the mocked out method to get a new instance but I always get the firstly created ResponseObject instance with the same Id:

try
{
    //I always get the same instance!!!
    responseObject = await basicClient.GetResponseAsync(new(){Id = Guid.NewGuid()}); 
}
catch (Exception e)
{
    Logger.LogError(e, e.Message);
}

Unfortunately the documentation is "quite" empty on this topic.

What should I change to get a new instance every time I call?

Answer 1

//...
.Returns(GetNewResponse());

will return the same instance provided when GetNewResponse() is invoked.

If you want a different instance per call then refactor the .Returns to invoke a delegate

//...
.Returns(() => GetNewResponse()); //<-- note the function in .Returns