Model thing = new Model();
        assertEquals(thing, thing);
    }

    @Test
    void testToStringNullSafe() {
        assertNotNull(new Model().toString());
    }

    @Test
    void testPropertiesClear() {
        // Test for issue #11552: NullPointerException when clearing properties
        Model model = new Model();
        model.addProperty("key1", "value1");
        model.addProperty("key2", "value2");