private void Arrange()
        {
            _mediator = new Mock <IMediator>();

            _mediator.Setup(mediator =>
                            mediator.Send(It.Is <RegisterGenre>(g => g.Name == "Genre1"), CancellationToken.None))
            .Returns(Task.FromResult(_genreId));

            _subject = new AssignGenresToTitleHandler(_mediator.Object, Context);
        }
        private void Arrange()
        {
            _mediator = new Mock <IMediator>();

            _subject = new AssignGenresToTitleHandler(_mediator.Object, Context);

            Context.TitleGenres.Add(new TitleGenre {
                TitleId = _titleId, GenreId = _keepGenreId
            });
            Context.TitleGenres.Add(new TitleGenre {
                TitleId = _titleId, GenreId = _removeGenreId
            });

            Context.SaveChanges();

            _mediator.Setup(mediator =>
                            mediator.Send(It.Is <RegisterGenre>(rg => rg.Name == _keepGenre), CancellationToken.None))
            .Returns(Task.FromResult(_keepGenreId));

            _mediator.Setup(mediator =>
                            mediator.Send(It.Is <RegisterGenre>(rg => rg.Name == "Genre2"), CancellationToken.None))
            .Returns(Task.FromResult(_removeGenreId));
        }