old_contents: import unittest
  from pyquebec.querybuilder import QueryBuilder
  
  class TestQueryBuilder(unittest.TestCase):
      def test_where_with_None_value(self):
          self.assertRaises(ValueError, QueryBuilder,None)
  
  if __name__ == '__main__':
      unittest.main()
  
new_contents: import unittest
  from unittest.mock import Mock,MagicMock
  from pyquebec.querybuilder import QueryBuilder
  
  class TestQueryBuilder(unittest.TestCase):
      @classmethod
      def setUpClass(cls):
          dbo_mock = Mock()
          cls._mock_db_instance = Mock()
          cls._mock_db_instance.dbo = MagicMock(return_value=dbo_mock)
  
      def test_querybuilderctor_nonedbinstance_then_raises_ValueError(self):
          self.assertRaises(ValueError, QueryBuilder,None)
  
      def test_querybuilderctor_validdbinstance_the_createavalidinstance(self):
          qb = QueryBuilder(self._mock_db_instance)
          self.assertIsNotNone(qb)
      
  if __name__ == '__main__':
      unittest.main()
  
subject: change unit test method name for a better one, start creating db mock instance and +1 ut