public async Task GetRandomAsyncBadRequestFailureTest()
        {
            // Arrange
            const string          invalidLevel      = "invalid";
            IQbQuestionService    qbQuestionService = Substitute.For <IQbQuestionService>();
            QbQuestionsController controller        = new QbQuestionsController(qbQuestionService, mapper);

            // Act
            IActionResult result = await controller.GetRandomAsync(invalidLevel);

            // Assert
            result.Should().BeOfType <BadRequestResult>();
        }
        public async Task GetRandomAsyncFailureTest()
        {
            // Arrange
            IQbQuestionService qbQuestionService = Substitute.For <IQbQuestionService>();
            QbQuestion         question          = null;

            qbQuestionService.GetRandomAsync(Arg.Any <int?>()).Returns(question);
            QbQuestionsController controller = new QbQuestionsController(qbQuestionService, mapper);

            // Act
            IActionResult result = await controller.GetRandomAsync(null);

            // Assert
            result.Should().BeOfType <NotFoundResult>();
        }