CompilerTest.java

@Test
    public void testDroolsContext() {
        String str =
                "global java.util.List list\n" +
                "\n" +
                "rule R when\n" +
                "then\n" +
                " list.add(kcontext);\n" +
                "end";

        KieSession ksession = getKieSession(str);

        List<Object> list = new ArrayList<>();
        ksession.setGlobal("list", list);
        ksession.fireAllRules();

        assertEquals( 1, list.size() );
    }