@Override
        public Progress process(Processing processing) {
            for (DocumentOperation op : processing.getDocumentOperations()) {
                assertEquals("calledTwice", processing.getVariable("processor1"));
                processing.setVariable("processor2", "called");
            }
            return Progress.DONE;
        }
Asserts that a document processing service works
docproc/src/test/java/com/yahoo/docproc/DocumentProcessingAbstractTestCase.java