List<ModelNode> getNodes() {
        return modelNodes;
    }
@Test
    void require_that_dependencies_are_correctly_set() {
        ModelGraphBuilder builder = new ModelGraphBuilder();
        builder.addBuilder(new GraphMock.BC()).addBuilder(new GraphMock.BB()).addBuilder(new GraphMock.BA());
        ModelGraph graph = builder.build();
        List<ModelNode> nodes = graph.getNodes();
        assertEquals(3, graph.getNodes().size());
        assertTrue(nodes.get(0).hasDependencies());
        assertTrue(nodes.get(1).hasDependencies());
        assertFalse(nodes.get(2).hasDependencies());
        assertTrue(nodes.get(0).dependsOn(nodes.get(1)));
        assertTrue(nodes.get(1).dependsOn(nodes.get(2)));
        assertFalse(nodes.get(2).dependsOn(nodes.get(0)));
    }