'loop_until can be passed a generator of intervals to wait on.'

@capture_logging(None)
def test_custom_time_steps(self, logger):

    result = object()
    results = [None, False, result]
    def predicate():
        return results.pop(0)
    clock = Clock()
    d = loop_until(clock, predicate, steps=[1, 2, 3])
    clock.advance(1)
    self.assertNoResult(d)
    clock.advance(1)
    self.assertNoResult(d)
    clock.advance(1)
    self.assertEqual(self.successResultOf(d), result)
