override = new GBeanOverride(gbeanType, new JexlExpressionParser());
override.setAttribute(gbeanInfo.getAttribute("bar1"), "foo", bundle);
override.setAttribute(gbeanInfo.getAttribute("bar2"), "foo", bundle);
override.getAttributes().put("foo", null);
GbeanType gbean = override.writeXml();
assertEquals(3, gbean.getAttributeOrReference().size());
AttributeType attribute = (AttributeType)gbean.getAttributeOrReference().get(2);
assertEquals("foo", attribute.getName());
assertTrue(attribute.isNull());
}