* @param content the content to add line numbers to
     * @return the content with line numbers prepended, or empty string if content is blank
     */
    public String appendLineNumber(final String prefix, final String content) {
        if (StringUtil.isBlank(content)) {
            return StringUtil.EMPTY;
        }
        final String[] values = content.split("\n");

        assertEquals("", documentHelper.appendLineNumber("L", null));
        assertEquals("", documentHelper.appendLineNumber("L", ""));
        assertEquals("", documentHelper.appendLineNumber("L", " "));
        assertEquals("", documentHelper.appendLineNumber("L", "\n"));
        assertEquals("", documentHelper.appendLineNumber("L", "\n\n"));
        assertEquals("", documentHelper.appendLineNumber("L", "\n \n"));