assertNotNull(results);
        }
    }

    /**
     * Test handling of documents with null ID field.
     */
    @Test
    public void test_documentsWithNullIdField() throws Exception {
        try (RankFusionProcessor processor = new RankFusionProcessor()) {
            processor.setSearcher(new TestSearcher(100));
            processor.register(new NullIdFieldSearcher());