Investigate use of Proxies for mocking

[jamesadarich]

Using proxies could get over the issue faced with interfaces having no definition at runtime however we'd need to make assumptions between functions and properties when determining what value to return

Mock<T>(T); // creates a mock based on the passed prototype

Mock<I>(); // creates a mock using a Proxy assuming all properties are FunctionSpies

Then properties should be overridden by something like

SetProperty(mock.property).to(42);

CallingFunction(mock.function).returns(42)

to define explicitly whether a property is a FunctionSpy or PropertySpy