'Should return only stream redirects if no files_preserve.'

def test_returns_stream_redirects_if_no_files_preserve(self):

    instance = self.test_instance
    instance.files_preserve = None
    expect_result = set((stream.fileno() for stream in self.stream_files_by_name.values()))
    result = instance._get_exclude_file_descriptors()
    self.failUnlessEqual(expect_result, result)
