assertEquals("********", SystemUtil.maskSensitiveValue("SMTP_PASSWORD", "secret123"));
    }

    @Test
    public void test_maskSensitiveValue_withSecret() {
        assertEquals("********", SystemUtil.maskSensitiveValue("AWS_SECRET_ACCESS_KEY", "AKIAIOSFODNN7EXAMPLE"));
        assertEquals("********", SystemUtil.maskSensitiveValue("secret", "mySecret"));