def METHOD_NAME(self):
    """
    Test that ``RegistrationFormUniqueEmail`` validates uniqueness
    of email addresses.
    """
    # Create a user so we can verify that duplicate addresses
    # aren't permitted.
    User.objects.create_user('alice', 'alice@example.com', 'secret')
    form = forms.RegistrationFormUniqueEmail(data={'username': 'foo',
                                                   'email': 'alice@example.com',
                                                   'password1': 'foo',
                                                   'password2': 'foo'})
    self.assertFalse(form.is_valid())
    self.assertEqual(form.errors['email'],
                     ["This email address is already in use. Please supply a different email address."])
    form = forms.RegistrationFormUniqueEmail(data={'username': 'foo',
                                                   'email': 'foo@example.com',
                                                   'password1': 'foo',
                                                   'password2': 'foo'})
    self.assertTrue(form.is_valid())