@Test
    public void requireThatIndexerForwardsUpdatesOfUnknownType() {
        var tester = new IndexingProcessorTester();
        DocumentUpdate input = new DocumentUpdate(new DocumentType("unknown"), "id:ns:music::");
        DocumentOperation output = tester.process(input);
        assertSame(input, output);
    }
Test sending assign of 1 field only, when needing 2.
TODO Vespa 9: This is allowed, but shouldn't be.
docprocs/src/test/java/com/yahoo/docprocs/indexing/IndexingProcessorTestCase.java