def test_saveResetsClobberState(self):
        """
        After L{KnownHostsFile.save} is used once with an instance initialized
        by the default initializer, contents of the save path are respected and
        preserved.
        """
        hostsFile = KnownHostsFile(self.pathWithContent(sampleHashedLine))
        preSave = hostsFile.addHostKey(
            b"www.example.com", Key.fromString(otherSampleKey))
        hostsFile.save()
        postSave = hostsFile.addHostKey(
            b"another.example.com", Key.fromString(thirdSampleKey))
        hostsFile.save()

        self.assertEqual([preSave, postSave], list(hostsFile.iterentries()))

        After L{KnownHostsFile.save} is used once with an instance initialized
        by the default initializer, contents of the save path are respected and
        preserved.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_knownhosts.py