}

    // Test getImageFilename with custom settings
    public void test_getImageFilename_customSettings() {
        thumbnailManager.setImageExtention("jpg");
        thumbnailManager.setSplitSize(5);
        thumbnailManager.setSplitHashSize(20);

        String docid = "1234567890abcdef";
        String filename = thumbnailManager.getImageFilename(docid);
        assertNotNull(filename);

        this.imageExtention = imageExtention;
    }

    /**
     * Sets the split size for directory organization.
     *
     * @param splitSize the split size to set
     */
    public void setSplitSize(final int splitSize) {
        this.splitSize = splitSize;
    }

    /**
     * Sets the maximum size of the thumbnail task queue.
     *
     * @param thumbnailTaskQueueSize the queue size to set