new_contents: import mock
  from linkr import db
  import database.common
  from test.backend.test_case import LinkrTestCase
  
  
  class TestCommon(LinkrTestCase):
      def test_create_tables(self):
          with mock.patch.object(db, 'create_all') as mock_create:
              database.common.create_tables()
  
              self.assertTrue(mock_create.called)
  
subject: Test database.common for full coverage of database