@Test
public void testCacheEmptying() throws Exception {

    URL resource = VariableOnlineResourceTest.class.getResource("3.gif");
    StringLiteral lit = new StringLiteral(resource.toString());
    VariableOnlineResource vor = new VariableOnlineResource(lit);
    PlanarImage first = vor.getPlanarJAI(null);
    PlanarImage second = vor.getPlanarJAI(null);
    assertTrue(first == second);
    lit.setValue(VariableOnlineResourceTest.class.getResource("21.gif").toString());
    lit.setValue(VariableOnlineResourceTest.class.getResource("3.gif").toString());
    PlanarImage third = vor.getPlanarJAI(null);
    assertFalse(third == second);
}