'Test that a LineBuffer flushes everything when its iterator is
exhausted, and itself raises StopIteration.'

def testFinishLineBuffering(self):

    output = []
    input = iter(['a', 'b', 'c'])
    c = pop3._IteratorBuffer(output.extend, input, 5)
    for i in c:
        pass
    self.assertEqual(output, ['a', 'b', 'c'])
