    @Test
    public void testSignalShouldNotPropagateEdgeIfNotEnoughSrcNodePotential() throws Exception {

        // tests when signal should propagate
        DGRN dgrn = getMockDGRN_twoNode();
        List<Edge> edges = dgrn.graph.getAllEdges();
        Assert.assertEquals(edges.size(), 1);  // only 1 edge in this graph
        Edge edge = edges.get(0);
        // init state:
        // (1) -2-> (0)
        Assert.assertEquals(dgrn.edgePropagatesSignal(edge), false);
    }