var mockSet = new Mock<DbSet<Posting>>();
mockSet.As<IQueryable<Posting>>().Setup(m => m.Provider).Returns(data.Provider);
mockSet.As<IQueryable<Posting>>().Setup(m => m.Expression).Returns(data.Expression);
mockSet.As<IQueryable<Posting>>().Setup(m => m.ElementType).Returns(data.ElementType);
mockSet.As<IQueryable<Posting>>().Setup(m => m.GetEnumerator()).Returns(data.GetEnumerator());
var mockContext = new Mock<CustomDbContext>();
mockContext.Setup(m => m.Postings).Returns(mockSet.Object);