*
     * @param keyPattern The pattern to filter environment variable keys.
     * @return A map of filtered environment variables.
     */
    public Map<String, String> getFilteredEnvMap(final String keyPattern) {
        final Pattern pattern = Pattern.compile(keyPattern);
        return getEnvMap().entrySet().stream().filter(e -> {
            final String key = e.getKey();

    }

    @Test
    public void test_getFilteredEnvMap() {
        Map<String, String> filteredEnvMap = systemHelper.getFilteredEnvMap("^FESS_ENV.*");
        assertEquals(0, filteredEnvMap.size());

        envMap.put("FESS_ENV_TEST", "123");
        filteredEnvMap = systemHelper.getFilteredEnvMap("^FESS_ENV.*");
        assertEquals(1, filteredEnvMap.size());
        assertEquals("123", filteredEnvMap.get("FESS_ENV_TEST"));