JSONObject config = new JSONObject('{' + ContainerConfig.DEFAULT_CONTAINER + ':' +
"{'gadgets.features':{opensocial:" +
"{supportedFields: {mediaItem: ['id', 'language', 'title']}}" +
"}}}");
containerConfig = new JsonContainerConfig(config, Expressions.forTesting());
handler = new MediaItemHandler(mediaService, containerConfig);
registry = new DefaultHandlerRegistry(null, converter,
new HandlerExecutionListener.NoOpHandler());
registry.addHandlers(ImmutableSet.<Object>of(handler));