'Set up a test to verify a key that isn\'t present.  Return a 3-tuple of
the UI, a list set up to collect the result of the verifyHostKey call,
and the sample L{KnownHostsFile} being used.
This utility method avoids returning a L{Deferred}, and records results
in the returned list instead, because the events which get generated
here are pre-recorded in the \'ui\' object.  If the L{Deferred} in
question does not fire, the it will fail quickly with an empty list.'

def verifyNonPresentKey(self):

    hostsFile = self.loadSampleHostsFile()
    absentKey = Key.fromString(thirdSampleKey)
    ui = FakeUI()
    l = []
    d = hostsFile.verifyHostKey(ui, 'sample-host.example.com', '4.3.2.1', absentKey)
    d.addBoth(l.append)
    self.assertEqual([], l)
    self.assertEqual(ui.promptText, "The    authenticity    of    host    'sample-host.example.com    (4.3.2.1)'    can't    be    established.\nRSA    key    fingerprint    is    SHA256:mS7mDBGhewdzJkaKRkx+wMjUdZb/GzvgcdoYjX5Js9I=.\nAre    you    sure    you    want    to    continue    connecting    (yes/no)?    ")
    return (ui, l, hostsFile)
