public void test_duplicateDocumentIds() throws Exception {
        try (RankFusionProcessor processor = new RankFusionProcessor()) {
            processor.setSearcher(new TestSearcherWithFixedIds("doc1", "doc2", "doc3"));
            processor.register(new TestSearcherWithFixedIds("doc2", "doc3", "doc4")); // Some duplicates
            processor.init();