public void test_getImageFilename_customSettings() {
        thumbnailManager.setImageExtention("jpg");
        thumbnailManager.setSplitSize(5);
        thumbnailManager.setSplitHashSize(20);

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

    }

    /**
     * Sets the hash size for splitting thumbnail storage directories.
     *
     * @param splitHashSize the hash size to set
     */
    public void setSplitHashSize(final int splitHashSize) {
        this.splitHashSize = splitHashSize;
    }