MOQ - how to mock an interface that needs to be cast to another interface?
Solution 1:
The way I understand you, you want to create a mock that implements two interfaces. With Moq, that is as simple as this:
var mock = new Mock<IFoo>(); // Creates a mock from IFoo
mock.As<IBar>(); // Adds IBar to the mock
mock.As<IBar>().Setup(m => m.BarMethod()).Returns(new object()); // For setups.
Now, you can set up expectations and use your mock as you would normally use the object implementing both IFoo and IBar.
For your GetNewInstance method, you can just set up an expectation that returns the mock itself.