public static String errorPage(int code, String message) {
        return Holder.INSTANCE.replaceAll(buildRegex("status_code"), valueOf(code))
                .replaceAll(buildRegex("error_message"), StringEscapeUtils.escapeHtml4(message));
    }
@Test
    public void shouldReplaceStatusCodeAndMessage() {
        assertThat(errorPage(404, "Error message"))
                .contains("<h1>404</h1>")
                .contains("<h2>Error message</h2>");
    }