If you are seeking assistance in the year 2020, I suggest visiting this particular webpage: https://www.selenium.dev/documentation/en/webdriver/waits/

I personally utilized the Explicit wait method and found it to be incredibly beneficial.

Although this may not directly address your question about slowing down the process, it does offer a potential solution to the issue you might be facing.

The key is not to make the steps run slower, but rather to ensure that no steps are executed until the page has fully loaded.

To tackle this problem, you can utilize methods like WebDriverWait and visibilityOfElementLocated.

I have made some additions to your code snippet below:

import static org.openqa.selenium.support.ui.ExpectedConditions.visibilityOfElementLocated;
import org.openqa.selenium.support.ui.WebDriverWait;


public static void main(String[] args) {

  //**********************************open ff
  WebDriver driver = new FirefoxDriver();
  WebDriverWait wait = new WebDriverWait(driver, 30);
  //**************************************maximize ff 

  driver.manage().window().maximize();

  Logger log = Logger.getLogger("devpinoyLogger");
  driver.get("http://navvitistgvm.cloudapp.net/nvrppluginassist/Account/Login");
  // The line below should ideally block execution until the page loads.
  // Try removing it from your code and observe the difference.
  // Wait till the username field is visible.
  wait.until(visibilityOfElementLocated(By.xpath("//*[@id='UserName']"))));

  log.debug("entering username");      
  driver.findElement(By.xpath("//*[@id='UserName']")).sendKeys("rpadmin");

  log.debug("entering password");
  driver.findElement(By.xpath("//*[@id='Password']")).sendKeys("Password123");

  log.debug("Clicking login");
  driver.findElement(By.xpath("//*[@id='loginForm']/form/div[4]/div/input")).click();

  // It seems there might be an issue here as well, where the view changes after clicking login.
  // To address this, add another wait.
  wait.until(visibilityOfElementLocated(By.xpath("html/body/nav/div[2]/div[2]/ul/li[2]/a")));

  log.debug("Clicking voucher");
  driver.findElement(By.xpath("html/body/nav/div[2]/div[2]/ul/li[2]/a")).click();

  log.debug("selecting search_voucher");

   List<WebElement> elements=driver.findElements(By.id("VoucherType"));
   //elements.get(0).click(); //GV
   elements.get(1).click();  //GC
   //elements.get(2).click();//AP

   driver.manage().timeouts().setScriptTimeout(30, TimeUnit.SECONDS);

  driver.findElement(By.xpath("//*[@id='main']/form[2]/div[2]/input[4]")).click();
  driver.manage().timeouts().setScriptTimeout(30, TimeUnit.SECONDS);
      driver.findElement(By.xpath("//*[@id='main']/div[1]/span/a")).click();
}
}

If you do wish for the code to execute "slower," although not recommended (as how slow should it go?), a better approach would be to conduct explicit testing using the method I have demonstrated above, incorporating waits only where necessary (e.g., page or view loading due to certain actions).

One strategy could involve encapsulating actions and applying a timeout, as shown in the example below:

public void waitAndClick(Xpath) {
  driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);
  driver.findElement(By.xpath(Xpath)).click();
}

However, I strongly encourage trying out the initial approach first, as it offers a more effective solution.

If you are encountering "no such element" exceptions in between actions, consider implementing an explicit wait strategy as suggested on this resource.

Avoid using excessive sleep statements!

To ensure smooth page loading or to wait for specific elements after clicking, it is recommended to utilize fluent wait in Selenium. This allows you to execute Selenium API calls only after the desired element has loaded:

If you want to learn more about how Fluent Wait works in Selenium, check out the documentation provided at: https://selenium.googlecode.com/git/docs/api/java/org/openqa/selenium/support/ui/FluentWait.html

If implicit and explicit waits are not working as expected, you can try using Thread.sleep(3000) for a 3-second delay.

For more information on execution speed, check out the following link: setSpeed in Selenium WebDriver using Ruby

I encountered a similar issue while working on my own code. Experimenting with the selenium API, I attempted the following approaches in my application:

WebDriverWait wait = new WebDriverWait(driver, 30);
wait.until(ExpectedConditions.elementToBeClickable(By.xpath("xpath")));
wait.until(visibilityOfElementLocated(By.xpath(xpath))); 

Although these methods improved the situation, I continued to face errors related to xpath not being located. It dawned on me that the waiting methods provided by Selenium were either too speedy or my elements weren't loading quickly enough.

To address this, I implemented the following additional delay within the code:

//Introducing extra wait time to accommodate Selenium's limitations as it sometimes loads too swiftly
        Random ran = new Random();
        //The variable x now holds a randomly generated number between 800 and 1200.
        int x = ran.nextInt(401) + 800;
        try {
            Thread.sleep(x);
        } catch (InterruptedException e) {
            // Handle interrupted exception
            e.printStackTrace();
        }