@Test
public void testAppendPanelTypeClassPrefixPanelTypeClassPrefixNull() throws Exception {

    // set up
    request.setAttribute(ResultMessages.DEFAULT_MESSAGES_ATTRIBUTE_NAME,
            ResultMessages.error().add(ResultMessage.fromText("foo")));
    tag.setPanelTypeClassPrefix(null);
    int ret = tag.doStartTag();
    String expected = "<div class=\"alerterror\"><ul><li>foo</li></ul></div>";
    // assert
    assertThat(getOutput(), is(expected));
    assertThat(ret, is(TagSupport.EVAL_BODY_INCLUDE));
}