@Test
    public void testExtends() {
        String str =
                "package mypkg;\n" +
                     "import " + Person.class.getCanonicalName() + ";" +
                     "rule R1 when\n" +
                     "  $p1 : Person($address : address)\n" +
                     "then\n" +
                     "end\n" +
                     "rule R2 extends R1 when\n" +
                     "  $p2 : Person(this != $p1, $address.city == address.city)\n" +
                     "then\n" +
                     "  insert(\"Done\");\n" +
                     "end\n" +
                     "rule R3 when\n" +
                     "  $p : String(this == \"Done\")\n" +
                     "then\n" +
                     "end\n";

        Person p1 = new Person("John");
        p1.setAddress(new Address("A1"));
        Person p2 = new Person("Paul");
        p2.setAddress(new Address("A1"));
        runRule(str, p1, p2);
        
        AnalysisModel analysisModel = new ModelBuilder().build(str);

        ModelToGraphConverter converter = new ModelToGraphConverter();
        Graph graph = converter.toGraph(analysisModel);

        assertLink(graph, "mypkg.R1", "mypkg.R2");
        assertLink(graph, "mypkg.R2", "mypkg.R3", ReactivityType.POSITIVE);
    }