private Hit createHitWithOnlyHiddenFields() {
        Hit h = new Hit("hiddenFields");
        h.setField("NaN", NanNumber.NaN);
        h.setField("emptyString", "");
        h.setField("emptyStringFieldValue", new StringFieldValue(""));
        h.setField("$vespaImplementationDetail", "Hello, World!");
        return h;
    }
Functional testing of {@link JsonRenderer}.

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