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;
        generator.target = true;

    }

    /**
     * Sets the maximum size of the thumbnail task queue.
     *
     * @param thumbnailTaskQueueSize the queue size to set
     */
    public void setThumbnailTaskQueueSize(final int thumbnailTaskQueueSize) {
        this.thumbnailTaskQueueSize = thumbnailTaskQueueSize;
    }

    /**
     * Sets the expiration time for no-image placeholder files.
     *