public ConfigPayloadBuilder getObject(String name) {
        ConfigPayloadBuilder p = objectMap.get(name);
        if (p == null) {
            validateObject(name);
            p = new ConfigPayloadBuilder(getStructDef(name));
            objectMap.put(name, p);
        }
        return p;
    }
@Test(expected=IllegalArgumentException.class)
    public void require_that_structs_must_exist() {
        builderWithDef.getObject("structdoesnotexist");
    }