old_contents: from unittest import TestCase
  
  from sqlalchemy import BigInteger, Column, String
  
  from tornado_sqlalchemy import declarative_base, make_session_factory
  
  
  postgres_url = 'postgres://t_sa:t_sa@localhost/t_sa'
  
  mysql_url = 'mysql://t_sa:t_sa@localhost/t_sa'
  
  sqlite_url = 'sqlite:///t_sa.sqlite3'
  
  Base = declarative_base()
  
  
  class User(Base):
      __tablename__ = 'users'
  
      id = Column(BigInteger, primary_key=True)
      username = Column(String(64), unique=True)
  
      def __init__(self, username):
          self.username = username
  
  
  class BaseTestCase(TestCase):
      def setUp(self):
          self.factory = make_session_factory(postgres_url)
  
          Base.metadata.create_all(self.factory.engine)
  
      def tearDown(self):
          Base.metadata.drop_all(self.factory.engine)
  
new_contents: from unittest import TestCase
  
  from sqlalchemy import BigInteger, Column, String
  
  from tornado_sqlalchemy import declarative_base, make_session_factory
  
  
  postgres_url = 'postgresql://t_sa:t_sa@localhost/t_sa'
  
  mysql_url = 'mysql://t_sa:t_sa@localhost/t_sa'
  
  sqlite_url = 'sqlite:///t_sa.sqlite3'
  
  Base = declarative_base()
  
  
  class User(Base):
      __tablename__ = 'users'
  
      id = Column(BigInteger, primary_key=True)
      username = Column(String(64), unique=True)
  
      def __init__(self, username):
          self.username = username
  
  
  class BaseTestCase(TestCase):
      def setUp(self):
          self.factory = make_session_factory(postgres_url)
  
          Base.metadata.create_all(self.factory.engine)
  
      def tearDown(self):
          Base.metadata.drop_all(self.factory.engine)
  
subject: update dialect in test case URL