public void ShouldCallLibraryStateUpdate()
        {
            var updateLibraryStateCalled = false;

            dynamic caller = new ExpandoObject();

            caller.updateLibraryState = new Action <object>((book) => {
                updateLibraryStateCalled = true;
            });

            _mockClients.Setup(m => m.Caller).Returns((ExpandoObject)caller);

            _hub.GetLibraryState("test");

            Assert.True(updateLibraryStateCalled);
        }