how to mock an interface that needs to be cast to another interface?
what I want to do is construct a moq for I1 - which is fine ... however in the course of the method that I am testing that uses this mock I need to cast it to I2 in order to access some properties that are not on I1
Interface I1
{ int AProperty{get;set;}}
Interface I2
{int AnotherProperty{get;set;}}
I then have some objects
Class O1 : I1 {}
and
Class O2 : O1 , I2 {}
the problem is that when i have an instance of a I2 implementing object I can cast it to I1 in order to access the methods that are implmented through that interface. In code this is not a problem and everythign works as expected.
The only problem comes when writing a unit test on that class.
The interfaces also expose a method called GetNewInstance which returns an initialised instance of the the implementing object cast into the IGetNewInstance interface ... i can usually mock this fine and make it return itself (and so I keep working with the mock object).
however when you try to cast this returned object of type I2 into I1 a null reference results - this makes sense as the mock object that implements I2 does not inherit from anything that inherits I1.
the question is how can i force the mock object to inherit from both I1 ansd I2 at the same time?
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.
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