public void Update_UnknownGuidPassed_ReturnsNotFoundResult()
        {
            // Arrange
            var nameMissingItem = new SubjectModel()
            {
                Id        = 50,
                Credits   = 3,
                TeacherId = 1
            };
            // Act
            var notFoundResult = studentsController.PutSubject(nameMissingItem.Id, nameMissingItem).Result;

            // Assert
            Assert.IsType <NotFoundResult>(notFoundResult);
        }