public void CountForUser_ReturnsCorrectUserReservations()
        {
            var options = new DbContextOptionsBuilder <ApplicationDbContext>().UseInMemoryDatabase(Guid.NewGuid().ToString()).Options;

            using (var dbContext = new ApplicationDbContext(options))
            {
                var user = new ApplicationUser {
                    UserName = "******", Email = "*****@*****.**"
                };
                Reservation reservation = new Reservation()
                {
                    VehicleMake         = "BMW",
                    VehicleModel        = "M5",
                    LicenseNumber       = "СА 1234 КР",
                    PhoneNumber         = "0897482124",
                    ReservationDateTime = new DateTime(2020, 3, 21, 10, 30, 10),
                    User = user,
                };

                var reservationsService = new ReservationsService(dbContext);

                dbContext.Reservations.Add(reservation);
                dbContext.SaveChanges();

                var result = reservationsService.CountForUser(user.UserName);

                Assert.Equal(1, result);
            }
        }