public void ThrowsWhenBatchUpdateThrows()
        {
            var observables = createObservables();

            dataSource.BatchUpdate(Arg.Any <IEnumerable <IThreadSafeTestModel> >()).Returns(
                Observable.Throw <IEnumerable <IConflictResolutionResult <IThreadSafeTestModel> > >(new TestException()));

            Action startingState = () => state.Start(observables).SingleAsync().Wait();

            startingState.Should().Throw <TestException>();
        }