private String render(Result r) throws InterruptedException, ExecutionException {
        Execution execution = new Execution(Execution.Context.createContextStub());
        return render(execution, r);
    }
Functional testing of {@link JsonRenderer}.

@author Steinar Knutsen
@author bratseth
container-search/src/test/java/com/yahoo/search/rendering/JsonRendererTestCase.java