How to properly mock DbContext (EF6 - database first)

[freddie]

Hi,

i found this: http://pipersgates.wordpress.com/2014/03/25/mocking-entity-framework-6-context-with-rhino-mocks-code-first/

and of course what Microsoft stated: http://msdn.microsoft.com/en-us/data/dn314429.aspx

But it fails when I am trying to adapt it.

[TestClass]

public class MyTestClass
{    
      [TestMethod]
      public void MyTestMethod(){
 
            var mockRepository = new MockRepository();

            var list = new List<Employee>

            {

                new Employee{ Id = 1},

                new Employee{ Id = 2},

                new Employee{ Id = 3}

            }.AsQueryable();

            var mockEntities = MockRepository.GenerateMock<Entities>();

            IDbSet<Employee> mockDbSet= MockRepository.GenerateMock<IDbSet<Employee>, IQueryable>();

            mockDbSet.AsQueryable().Stub(m => m.Provider).Return(list .Provider);

            mockDbSet.AsQueryable().Stub(m => m.Expression).Return(list .Expression);

            mockDbSet.AsQueryable().Stub(m => m.ElementType).Return(list .ElementType);

            mockDbSet.AsQueryable().Stub(m => m.GetEnumerator()).Return(list .GetEnumerator());

            mockEntities.Stub(x => x.Employees).PropertyBehavior();

            mockEntities.Employees = mockDbSet as DbSet<Employee>;

            int expected = list .Count();

            var employeesService= mockRepository.PartialMock<EmployeesService>();

            int actual = employeesService.GetCount();

            Assert.AreEqual(expected, actual);

            mockRepository.VerifyAll();

       }
}

public partial class Entities : DbContext

{

        public Entities()

            : base("name=Entities")

        {

        }

    

        protected override void OnModelCreating(DbModelBuilder modelBuilder)

        {

            throw new UnintentionalCodeFirstException();

        }

    

        public virtual DbSet<Employee> Employees{ get; set; }
}


public class EmployeesService
{
     Entities context;

     public EmployeeService(Entities context)
     {
        this.context=context;
     }

           public int GetCount()

           {                   

                  return context.Employees.Count();                    

           }
}

mockDbSet is null after save casting to DbSet<Employee>. Therefor GetCount() throws a nullpointerreference because the property Employees is not set. 

Does anyone know what I am doing wrong? 

It is just a sample, no guarantee the code works as stated. ;) it just visualize things. 

Thanks!!

[haifisch]

Why do you need the cast to DbSet, couldn't you just use IDbSet?
For sure you couldn't cast a stubbed instance of IDbSet to DbSet because your stubbed instance doesn't inherit from DbSet.
Br,
Andreas