docMap.put("_id", "docid1");

        boolean result = thumbnailManager.offer(docMap);
        assertFalse(result);
    }

    // Test offer with full queue
    public void test_offer_fullQueue() {
        thumbnailManager.setThumbnailTaskQueueSize(1);
        thumbnailManager.init();

        TestThumbnailGenerator generator = new TestThumbnailGenerator();
        generator.available = true;