public void LogInUser() { var data = new List <User> { new User { FirstName = "Stamat", LastName = "Stamatov", Age = 13, Email = "*****@*****.**", PhoneNumber = "0877253698", Username = "******", Password = "******", ConfirmPassword = "******", IsEmployer = false } }.AsQueryable(); var mockSet = new Mock <DbSet <User> >(); mockSet.As <IQueryable <User> >().Setup(u => u.Provider).Returns(data.Provider); mockSet.As <IQueryable <User> >().Setup(u => u.Expression).Returns(data.Expression); mockSet.As <IQueryable <User> >().Setup(u => u.ElementType).Returns(data.ElementType); mockSet.As <IQueryable <User> >().Setup(u => u.GetEnumerator()).Returns(data.GetEnumerator()); var mockContext = new Mock <JobApplicationDbContext>(); mockContext.Setup(c => c.Users).Returns(mockSet.Object); var service = new UserService(mockContext.Object); var users = data.ToList(); users.ForEach(u => service.Register(u.FirstName, u.LastName, u.Age.Value, u.Email, u.PhoneNumber, u.Username, u.Password, u.ConfirmPassword, u.IsEmployer)); int logInResult = service.Login(users[0].Username, users[0].Password); Assert.AreEqual(0, logInResult); }