text: from unittest import TestCase
  
  from django.core.exceptions import ValidationError
  from django.db import models
  
  
  class ValidationMessagesTest(TestCase):
  
      def _test_validation_messages(self, field, value, expected):
          with self.assertRaises(ValidationError) as cm:
              field.clean(value, None)
          self.assertEqual(cm.exception.messages, expected)
  
      def test_autofield_field_raises_error_message(self):
          f = models.AutoField(primary_key=True)
          self._test_validation_messages(f, 'fõo', ["'fõo' value must be an integer."])
  
      def test_integer_field_raises_error_message(self):
          f = models.IntegerField()
          self._test_validation_messages(f, 'fõo', ["'fõo' value must be an integer."])
  
      def test_boolean_field_raises_error_message(self):
          f = models.BooleanField()
          self._test_validation_messages(f, 'fõo', ["'fõo' value must be either True or False."])
  
      def test_float_field_raises_error_message(self):
          f = models.FloatField()
          self._test_validation_messages(f, 'fõo', ["'fõo' value must be a float."])
  
      def test_decimal_field_raises_error_message(self):
          f = models.DecimalField()
          self._test_validation_messages(f, 'fõo', ["'fõo' value must be a decimal number."])
  
      def test_null_boolean_field_raises_error_message(self):
          f = models.NullBooleanField()
          self._test_validation_messages(f, 'fõo', ["'fõo' value must be either None, True or False."])
  
      def test_date_field_raises_error_message(self):
          f = models.DateField()
          self._test_validation_messages(
              f, 'fõo',
              ["'fõo' value has an invalid date format. It must be in YYYY-MM-DD format."]
          )
          self._test_validation_messages(
              f, 'aaaa-10-10',
              ["'aaaa-10-10' value has an invalid date format. It must be in YYYY-MM-DD format."]
          )
          self._test_validation_messages(
              f, '2011-13-10',
              ["'2011-13-10' value has the correct format (YYYY-MM-DD) but it is an invalid date."]
          )
          self._test_validation_messages(
              f, '2011-10-32',
              ["'2011-10-32' value has the correct format (YYYY-MM-DD) but it is an invalid date."]
          )
  
      def test_datetime_field_raises_error_message(self):
          f = models.DateTimeField()
          # Wrong format
          self._test_validation_messages(
              f, 'fõo',
              ["'fõo' value has an invalid format. It must be in YYYY-MM-DD HH:MM[:ss[.uuuuuu]][TZ] format."]
          )
          # Correct format but invalid date
          self._test_validation_messages(
              f, '2011-10-32',
              ["'2011-10-32' value has the correct format (YYYY-MM-DD) but it is an invalid date."]
          )
          # Correct format but invalid date/time
          self._test_validation_messages(
              f, '2011-10-32 10:10',
              ["'2011-10-32 10:10' value has the correct format (YYYY-MM-DD HH:MM[:ss[.uuuuuu]][TZ]) "
               "but it is an invalid date/time."]
          )
  
      def test_time_field_raises_error_message(self):
          f = models.TimeField()
          # Wrong format
          self._test_validation_messages(
              f, 'fõo',
              ["'fõo' value has an invalid format. It must be in HH:MM[:ss[.uuuuuu]] format."]
          )
          # Correct format but invalid time
          self._test_validation_messages(
              f, '25:50',
              ["'25:50' value has the correct format (HH:MM[:ss[.uuuuuu]]) but it is an invalid time."]
          )
  