text: import pytest     # http://pytest.readthedocs.io/en/stable/
  
  
  def defaultdateimage():
    return 'datetimeweb/date:latest'
  
  
  def defaulttimeimage():
    return 'datetimeweb/time:latest'
  
  
  def defaultwebimage():
    return 'datetimeweb/web:latest'
  
  
  def pytest_addoption(parser):
    parser.addoption('--dateimage',
                     action = 'store',
                     default = None,
                     help = 'Default:  %s' % ( defaultdateimage() ))
    parser.addoption('--timeimage',
                     action = 'store',
                     default = None,
                     help = 'Default:  %s' % ( defaulttimeimage() ))
    parser.addoption('--webimage',
                     action = 'store',
                     default = None,
                     help = 'Default:  %s' % ( defaultwebimage() ))
  
  
  @pytest.fixture(scope = 'session')
  def dateimage(request):
    image = request.config.getoption('--dateimage')
    return image if image is not None else defaultdateimage()
  
  
  @pytest.fixture(scope = 'session')
  def timeimage(request):
    image = request.config.getoption('--timeimage')
    return image if image is not None else defaulttimeimage()
  
  
  @pytest.fixture(scope = 'session')
  def webimage(request):
    image = request.config.getoption('--webimage')
    return image if image is not None else defaultwebimage()
  