public async Task GetDeckAssignmentsByDeck_UnknownIdPassed_ReturnsNull()
        {
            // Arrange
            var controller    = new DeckAssignmentsController(flashcardDbContextMock.Object, GetMockUserManager().Object, emailService, logger);
            int unknownDeckId = 22;

            // Act
            var result = await controller.GetDeckAssignmentsByDeck(unknownDeckId);

            // Asssert
            Assert.Null(result.Result);
        }
        public async Task GetDeckAssignmentsByDeck_ReturnsAllAssignments()
        {
            // Arrange
            var controller = new DeckAssignmentsController(flashcardDbContextMock.Object, GetMockUserManager().Object, emailService, logger);
            int deckId     = 1;

            // Act
            var result = await controller.GetDeckAssignmentsByDeck(deckId);

            // Asssert
            var assignments = Assert.IsType <List <DeckAssignmentDTO> >(result.Value);

            Assert.Equal(1, assignments.Count);
        }