public void AddMarkToDatabase()
{
// Arrange
var classes = new List <StudentClass>();
var queryable = classes.AsQueryable();
var mockDbSet = new Mock <IDbSet <StudentClass> >();
mockDbSet.As <IQueryable <StudentClass> >().Setup(m => m.Provider).Returns(queryable.Provider);
mockDbSet.As <IQueryable <StudentClass> >().Setup(m => m.Expression).Returns(queryable.Expression);
mockDbSet.As <IQueryable <StudentClass> >().Setup(m => m.ElementType).Returns(queryable.ElementType);
mockDbSet.As <IQueryable <StudentClass> >().Setup(m => m.GetEnumerator()).Returns(() => queryable.GetEnumerator());
mockDbSet.Setup(d => d.Add(It.IsAny <StudentClass>())).Callback <StudentClass>((cl) => classes.Add(cl));
var mockDbContext = new Mock <IDatabaseContext>();
mockDbContext.Setup(c => c.StudentClasses).Returns(mockDbSet.Object);
var studentClassService = new StudentClassService(mockDbContext.Object);
var studentClass = new StudentClass("1A");
// Act
studentClassService.Add(studentClass);
// Assert
Assert.IsTrue(classes.Count() == 1);
Assert.IsTrue(classes.Contains(studentClass));
}