def test_subpipe_input_set_as_expected(self):
a = Mock(output=lambda: list('abc'))
b = Mock(output=lambda: list('def'))
c = Mock(output=lambda: list('beg'))
def ugh(x):
x.input = c.output
c.link = Mock(side_effect=ugh)
subpipe = BasePipe()
subpipe.add(a, b)
pipe = BasePipe()
pipe.add(c, subpipe) # should not raise
c.link.assert_called_once_with(subpipe)
self.assertEqual(subpipe.input(), c.output())
