private JsonReader createReader(String jsonInput) {
        InputStream input = new ByteArrayInputStream(Utf8.toBytes(jsonInput));
        return new JsonReader(types, input, parserFactory);
    }
Basic test of JSON streams to Vespa document instances.

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