int result = this.tag.doStartTag();
assertEquals(BodyTag.EVAL_BODY_BUFFERED, result);
assertNotNull(getPageContext().getAttribute(ErrorsTag.MESSAGES_ATTRIBUTE));
assertTrue(getPageContext().getAttribute(ErrorsTag.MESSAGES_ATTRIBUTE) instanceof List);
String bodyContent = "Foo";
this.tag.setBodyContent(new MockBodyContent(bodyContent, getWriter()));
this.tag.doEndTag();
this.tag.doFinally();
assertEquals(bodyContent, getOutput());
assertEquals(existingAttribute,
getPageContext().getAttribute(ErrorsTag.MESSAGES_ATTRIBUTE, PageContext.APPLICATION_SCOPE));