Moq & EF6 - Mocking EF6 Delete method that does not delete an object

Question

I'm trying to make fun of my EF6 DbContext, and it works for the methods Add, Update, Find. But it does not work by method Removefor an unknown reason.

In theory, after deletion, the collection Studentsshould have only 1 return on the left. But he continues to return Count-2.

I put 3 Moq .Verifychecks to make sure that all methods are called and they are executed. But this is not the removal of an object from the collection of students.

If I commented on a line Assert.Equalthat checks the number of samples, the whole test passed.

Delete XUnit Method

[Fact]
public void Delete()
{            
    Mock<DbContexts.MVCWebAppDbContext> dbContext = new Mock<DbContexts.MVCWebAppDbContext>();
    IStudentsService studentService = new StudentsService(dbContext.Object);

    var students = new List<Student>()
    {
        new Student() { StudentID = 1, RefNo = "12456343", FirstName = "John", LastName = "Smith", DateOfBirth = DateTime.Now.AddYears(-10), DateCreated = DateTime.Now },
        new Student() { StudentID = 2, RefNo = "87984564", FirstName = "Pete", LastName = "Luck", DateOfBirth = DateTime.Now.AddYears(-20), DateCreated = DateTime.Now.AddDays(1) }
    };

    var mockSet = new Mock<DbSet<Student>>();
    mockSet.As<IQueryable<Student>>().Setup(m => m.Provider).Returns(students.AsQueryable().Provider);
    mockSet.As<IQueryable<Student>>().Setup(m => m.Expression).Returns(students.AsQueryable().Expression);
    mockSet.As<IQueryable<Student>>().Setup(m => m.ElementType).Returns(students.AsQueryable().ElementType);
    mockSet.As<IQueryable<Student>>().Setup(m => m.GetEnumerator()).Returns(students.AsQueryable().GetEnumerator());

    mockSet.Setup(m => m.Remove(It.IsAny<Student>())).Callback<Student>((entity) => students.Remove(entity));

    dbContext.Setup(c => c.Students).Returns(mockSet.Object);

    int idToDelete = 1;

    dbContext.Setup(s => s.Students.Find(idToDelete)).Returns(students.Single(s => s.StudentID == idToDelete));

    // call delete method now
    studentService.Delete(idToDelete);

    // 1 object deleted, it should return 1
    Assert.Equal(1, students.Count());  // <----- Error here

    dbContext.Verify(s => s.Students.Find(idToDelete), Times.Once);
    dbContext.Verify(s => s.Students.Remove(It.IsAny<Student>()), Times.Once);
    dbContext.Verify(s => s.SaveChanges(), Times.Once);
}

StudentService.cs removal method

MVCWebAppDbContext _context;

public StudentsService(MVCWebAppDbContext context)
{
    _context = context;
}

public int Delete(int id)
{
    var objToDelete = _context.Students.Find(id);

    if (objToDelete != null)
    {
        _context.Students.Remove(objToDelete);
        return _context.SaveChanges();
    }

    return -1;
}

Could you guys help me with this removal method, mocking?

Answer 1

mockSet
    .Setup(m => m.Remove(It.IsAny<Student>()))
    .Callback<Student>((entity) => students.Remove(entity));

dbContext
    .Setup(m => m.Students.Remove(It.IsAny<Student>()))
    .Callback<Student>((entity) => students.Remove(entity));

DbContext.Students, DbSet.Remove

DbSet mocking,

[Fact]
public void Delete() {
    var dbContext = new Mock<DbContexts.MVCWebAppDbContext>();
    IStudentsService studentService = new StudentsService(dbContext.Object);

    var students = new List<Student>()
    {
        new Student() { StudentID = 1, RefNo = "12456343", FirstName = "John", LastName = "Smith", DateOfBirth = DateTime.Now.AddYears(-10), DateCreated = DateTime.Now },
        new Student() { StudentID = 2, RefNo = "87984564", FirstName = "Pete", LastName = "Luck", DateOfBirth = DateTime.Now.AddYears(-20), DateCreated = DateTime.Now.AddDays(1) }
    };

    dbContext
        .Setup(m => m.Students.Remove(It.IsAny<Student>()))
        .Callback<Student>((entity) => students.Remove(entity));

    int idToDelete = 1;

    dbContext
        .Setup(s => s.Students.Find(idToDelete))
        .Returns(students.Single(s => s.StudentID == idToDelete));

    // call delete method now
    studentService.Delete(idToDelete);

    // 1 object deleted, it should return 1
    Assert.AreEqual(1, students.Count());

    dbContext.Verify(s => s.Students.Find(idToDelete), Times.Once);
    dbContext.Verify(s => s.Students.Remove(It.IsAny<Student>()), Times.Once);
    dbContext.Verify(s => s.SaveChanges(), Times.Once);
}