'When L{HistoricRecvLine} receives a printable character,
it adds it to the current line buffer.'

def test_printableCharacters(self):

    self.p.keystrokeReceived('x', None)
    self.p.keystrokeReceived('y', None)
    self.p.keystrokeReceived('z', None)
    self.assertEqual(self.p.currentLineBuffer(), ('xyz', ''))
