new_contents: '''Test case for MongoDB database backend
  '''
  import unittest
  
  from lighty.db import fields, models
  
  
  class ModelTestCase(unittest.TestCase):
      '''Test case
      '''
  
      def testClassExtending(self):
          '''Test is child class inherit all the field from parent class
          '''
          class Base(models.Model):
              title = fields.CharField()
  
          class Child(Base):
              text = fields.TextField()
  
          assert 'title' in Child._fields, (
                          'Error on model class extending: %s' % Child._fields)
          assert isinstance(Child.title, fields.CharField), (
                          'Error on model class extending: %s' % Child.title)
  
  
  def test():
      suite = unittest.TestSuite()
      suite.addTest(ModelTestCase('testClassExtending'))
      return suite
  
subject: Add test case for model class inheritance