'L{MXCalculator.getMX} returns the MX record with the lowest preference
if it was last marked bad longer than L{MXCalculator.timeOutBadMX}
seconds ago.'

def test_badExchangeExpires(self):

    domain = 'example.com'
    good = 'good.example.com'
    previouslyBad = 'bad.example.com'
    records = [RRHeader(name=domain, type=Record_MX.TYPE, payload=Record_MX(0, previouslyBad)), RRHeader(name=domain, type=Record_MX.TYPE, payload=Record_MX(1, good))]
    self.mx.markBad(previouslyBad)
    self.clock.advance(self.mx.timeOutBadMX)
    return self._exchangeTest(domain, records, previouslyBad)
