public Progress process(Processing processing) {
            DocumentPut put = (DocumentPut)processing.getDocumentOperations().get(0);
            Document document = put.getDocument();
            document.setFieldValue("t", new StringFieldValue("The T"));
            document.removeFieldValue("a");
            document.setFieldValue("y", new IntegerFieldValue(2011));
            document.setFieldValue("i", new StringFieldValue("ISBN YEP"));
            return Progress.DONE;
        }
Tests vespa-documentgen-plugin

@author vegardh
documentgen-test/src/test/java/com/yahoo/vespa/config/DocumentGenPluginTest.java