'L{TwistOptions.selectDefaultLogObserver} will not override an already
selected observer.'

def test_selectDefaultLogObserverNoOverride(self):

    self.patchOpen()
    options = TwistOptions()
    options.opt_log_format('text')
    options.opt_log_file('queso')
    options.selectDefaultLogObserver()
    self.assertIdentical(options['fileLogObserverFactory'], textFileLogObserver)
    self.assertEqual(options['logFormat'], 'text')
