private void registerMirrorsDocumentType() {
        DocumentType x = new DocumentType("mirrors");
        StructDataType woo = new StructDataType("woo");
        woo.addField(new Field("sandra", DataType.STRING));
        woo.addField(new Field("cloud", DataType.STRING));
        x.addField(new Field("skuggsjaa", woo));
        types.registerDocumentType(x);
    }
Functional tests for com.yahoo.document.json.JsonWriter.

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