public void ReturnAllClasses()
        {
            // Arrange
            var classes = new List <StudentClass>()
            {
                new StudentClass("1A"),
                new StudentClass("2A"),
                new StudentClass("3A")
            }.AsQueryable();


            var mockedDbSet = new Mock <IDbSet <StudentClass> >();

            mockedDbSet.As <IQueryable <StudentClass> >().Setup(m => m.Provider).Returns(classes.Provider);
            mockedDbSet.As <IQueryable <StudentClass> >().Setup(m => m.Expression).Returns(classes.Expression);
            mockedDbSet.As <IQueryable <StudentClass> >().Setup(m => m.ElementType).Returns(classes.ElementType);
            mockedDbSet.As <IQueryable <StudentClass> >().Setup(m => m.GetEnumerator()).Returns(() => classes.GetEnumerator());

            var mockedDbContext = new Mock <IDatabaseContext>();

            mockedDbContext.Setup(c => c.StudentClasses).Returns(mockedDbSet.Object);

            var studentClassService = new StudentClassService(mockedDbContext.Object);

            // Act
            var allClasses = studentClassService.GetAll().ToList();

            // Assert
            CollectionAssert.AreEqual(classes, allClasses);
        }