def METHOD_NAME(target):
    from labgrid.strategy import GraphStrategy, InvalidGraphStrategyError
    class TestStrategy(GraphStrategy):
        def state_Root(self):
            pass
        @GraphStrategy.depends('Root')
        def state_A(self):
            pass
        @GraphStrategy.depends('Root', 'A', 'C')
        def state_B(self):
            pass
    with pytest.raises(InvalidGraphStrategyError) as e:
        TestStrategy(target, 'strategy')
    assert e.value.msg.startswith("B: State 'C' is unknown")