old_contents: from django.test import TestCase
  from users.models import User
  
  from django.core.exceptions import ValidationError
  
  
  class UserPhonenumberTest(TestCase):
      def setUp(self):
          self.user = User()
          self.valid_email = "test@example.com"
          self.valid_password = "test_password"
  
          self.valid_phonenumber = "12345678"
          self.invalid_short_phonenumber = "1234567"
          self.invalid_not_digit_phonenumber = "1234567a"
  
      def test_user_should_have_phonenumber_field(self):
          try:
              self.user.phonenumber
          except AttributeError:
              self.fail("User should have phonenumber field")
  
      def test_user_phonenumber_is_at_least_8_digit(self):
          self.user.phonenumber = self.valid_phonenumber
          self.assertGreaterEqual(len(self.user.phonenumber), 8, "phone number is less than 8")
  
      def test_user_with_short_phonenumber_should_not_be_valid(self):
          self.assertRaises(ValidationError, User.objects.create_user,
                            email=self.valid_email,
                            password=self.valid_password,
                            phonenumber=self.invalid_short_phonenumber)
new_contents: from django.test import TestCase
  from users.models import User
  
  from django.core.exceptions import ValidationError
  
  
  class UserPhonenumberTest(TestCase):
      def setUp(self):
          self.user = User()
          self.valid_email = "test@example.com"
          self.valid_password = "test_password"
  
          self.valid_phonenumber = "12345678"
          self.invalid_short_phonenumber = "1234567"
          self.invalid_not_digit_phonenumber = "1234567a"
  
      def test_user_should_have_phonenumber_field(self):
          try:
              self.user.phonenumber
          except AttributeError:
              self.fail("User should have phonenumber field")
  
      def test_user_phonenumber_is_at_least_8_digit(self):
          self.user.phonenumber = self.valid_phonenumber
          self.assertGreaterEqual(len(self.user.phonenumber), 8, "phone number is less than 8")
  
      def test_user_with_short_phonenumber_should_not_be_valid(self):
          self.assertRaises(ValidationError, User.objects.create_user,
                            email=self.valid_email,
                            password=self.valid_password,
                            phonenumber=self.invalid_short_phonenumber)
  
      def test_user_with_digit_should_not_be_valid(self):
          self.assertRaises(ValidationError, User.objects.create_user,
                              email=self.valid_email,
                              password=self.valid_password,
                              phonenumber=self.invalid_not_digit_phonenumber)
subject: add regex validation method for phone number