old_contents: import pytest
  
  TRANSITION_CLASS_NAMES = (
      'ShaderTransition', 'SlideTransition', 'SwapTransition', 'FadeTransition',
      'WipeTransition', 'FallOutTransition', 'RiseInTransition', 'NoTransition',
      'CardTransition',
  )
  
  
  def test_switch_to():
      import kivy.uix.screenmanager as sm
      manager = sm.ScreenManager()
      screen1 = sm.Screen(name='first')
      screen2 = sm.Screen(name='second')
      manager.switch_to(screen1)
      manager.switch_to(screen2)
      manager.switch_to(screen1)
      manager.switch_to(screen2)
      manager.current = 'first'
      manager.switch_to(screen1)
      manager.current = 'second'
      manager.switch_to(screen2)
  
  
  @pytest.mark.parametrize('transition_cls_name', TRANSITION_CLASS_NAMES)
  def test_switching_does_not_affect_a_list_of_screens(transition_cls_name):
      import kivy.uix.screenmanager as sm
      transition_cls = getattr(sm, transition_cls_name)
      scrmgr = sm.ScreenManager()
      for i in range(3):
          scrmgr.add_widget(sm.Screen(name=str(i)))
      names = scrmgr.screen_names.copy()
      scrmgr.transition = transition_cls()
      scrmgr.current = '1'
      assert names == scrmgr.screen_names
      scrmgr.transition = transition_cls()
      scrmgr.current = '2'
      assert names == scrmgr.screen_names
  
new_contents: import pytest
  
  TRANSITION_CLASS_NAMES = (
      'ShaderTransition', 'SlideTransition', 'SwapTransition', 'FadeTransition',
      'WipeTransition', 'FallOutTransition', 'RiseInTransition', 'NoTransition',
      'CardTransition',
  )
  
  
  def test_switch_to():
      import kivy.uix.screenmanager as sm
      manager = sm.ScreenManager()
      screen1 = sm.Screen(name='first')
      screen2 = sm.Screen(name='second')
      manager.switch_to(screen1)
      manager.switch_to(screen2)
      manager.switch_to(screen1)
      manager.switch_to(screen2)
      manager.current = 'first'
      manager.switch_to(screen1)
      manager.current = 'second'
      manager.switch_to(screen2)
  
  
  @pytest.mark.parametrize('transition_cls_name', TRANSITION_CLASS_NAMES)
  def test_switching_does_not_affect_a_list_of_screens(transition_cls_name):
      import kivy.uix.screenmanager as sm
      transition_cls = getattr(sm, transition_cls_name)
      scrmgr = sm.ScreenManager()
      for i in range(3):
          scrmgr.add_widget(sm.Screen(name=str(i)))
      names = list(scrmgr.screen_names)
      scrmgr.transition = transition_cls()
      scrmgr.current = '1'
      assert names == scrmgr.screen_names
      scrmgr.transition = transition_cls()
      scrmgr.current = '2'
      assert names == scrmgr.screen_names
  
subject: fix python2 incompatibility