Key press simulation in unit testing

I wrote below code to press three tab keys after that press enter key using robot. But it doesn't work as expected.

public void test_11() throws InterruptedException, AWTException {
    Robot robot=new Robot();

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