def test_mutuallyExclusiveCornerCase(self):
        """
        Exercise a corner-case of ZshArgumentsGenerator.makeExcludesDict()
        where the long option name already exists in the `excludes` dict being
        built.
        """
        class OddFighterAceOptions(FighterAceExtendedOptions):
            # since "fokker", etc, are already defined as mutually-
            # exclusive on the super-class, defining them again here forces
            # the corner-case to be exercised.
            optFlags = [['anatra', None,
                         'Select the Anatra DS as your dogfighter aircraft']]
            compData = Completions(
                            mutuallyExclusive=[['anatra', 'fokker', 'albatros',
                                                'spad', 'bristol']])

        opts = OddFighterAceOptions()
        ag = _shellcomp.ZshArgumentsGenerator(opts, 'ace', BytesIO())

        expected = {
             'albatros': set(['anatra', 'b', 'bristol', 'f',
                              'fokker', 's', 'spad']),
             'anatra': set(['a', 'albatros', 'b', 'bristol',
                            'f', 'fokker', 's', 'spad']),
             'bristol': set(['a', 'albatros', 'anatra', 'f',
                             'fokker', 's', 'spad']),
             'fokker': set(['a', 'albatros', 'anatra', 'b',
                            'bristol', 's', 'spad']),
             'spad': set(['a', 'albatros', 'anatra', 'b',
                          'bristol', 'f', 'fokker'])}

        self.assertEqual(ag.excludes, expected)

        Exercise a corner-case of ZshArgumentsGenerator.makeExcludesDict()
        where the long option name already exists in the `excludes` dict being
        built.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/test/test_shellcomp.py