Selenium键盘事件代码在Mac OS上不起作用

Question

我有一个键盘事件代码，但是此代码在mac os High Sierra版本10.13.4上不起作用。

只能听到蜂鸣声且未执行键盘操作

WebDriver driver = new ChromeDriver(); 
driver.get("http://newtours.demoaut.com/");

Actions mouse = new Actions(driver);
WebElement Register = driver.findElement(By.linkText("REGISTER"));

mouse.contextClick(Register).build().perform();

Thread.sleep(2000);

try {

    Robot robot = new Robot();
    for(int i=0;i<2;i++) {
        robot.keyPress(KeyEvent.VK_DOWN);
        robot.keyRelease(KeyEvent.VK_DOWN);
        Thread.sleep(2000);
    }

    robot.keyPress(KeyEvent.VK_ENTER);
    robot.keyRelease(KeyEvent.VK_ENTER);
}