private String fieldStringFromBase64RawContent(String base64data) throws IOException {
        Document doc = docFromJson("""
                                   {
                                     "put": "id:unittest:testraw::whee",
                                     "fields": {
                                       "actualraw": "%s"
                                     }
                                   }
                                   """.formatted(base64data));
        FieldValue f = doc.getFieldValue(doc.getField("actualraw"));
        assertSame(Raw.class, f.getClass());
        Raw s = (Raw) f;
        return Utf8.toString(s.getByteBuffer());
    }
Basic test of JSON streams to Vespa document instances.

@author Steinar Knutsen
@author bratseth
document/src/test/java/com/yahoo/document/json/JsonReaderTestCase.java