def METHOD_NAME(self):
    """Test unsuccessful registration (email already exists)"""
    self.user_login('test')
    user = User.objects.get(username='test')
    token = Token.objects.get(user=user)
    response = self.client.post(
        reverse('api_register'), {
            'username': 'restapi',
            'email': 'admin@example.com',
            'password': 'AekaiLe0ga'
        },
        Authorization=f'Token {token.key}'
    )
    self.assertEqual(response.status_code, HTTP_400_BAD_REQUEST)