Question

I am new to Selenium WebDriver and am trying to understand the correct way to ‘wait’ for elements to be present.

I am testing a page with a bunch of questions that have radio button answers. As you select answers, Javascript may enable/disable some of the questions on the page.

The problem seems to be that Selenium is ‘clicking too fast’ and not waiting for the Javascript to finish. I have tried solving this problem in two ways – explicit waits solved the problem. Specifically, this works, and solves my issue:

private static WebElement findElement(final WebDriver driver, final By locator, final int timeoutSeconds) {
    FluentWait<WebDriver> wait = new FluentWait<WebDriver>(driver)
            .withTimeout(timeoutSeconds, TimeUnit.SECONDS)
            .pollingEvery(500, TimeUnit.MILLISECONDS)
            .ignoring(NoSuchElementException.class);

    return wait.until(new Function<WebDriver, WebElement>() {
        public WebElement apply(WebDriver webDriver) {
            return driver.findElement(locator);
        }
    });
}

However, I would prefer to use an implicit wait instead of this. I have my web driver configured like this:

driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);

This does not solve the problem and I get a NoSuchElementException. Additionally, I do not notice a 10 second pause – it just errors out immediately. I have verified this line in the code is being hit with a debugger. What am I doing wrong? Why does implicitlyWait not wait for the element to appear, but FluentWait does?

Note: As I mentioned I already have a work around, I really just want to know why Implicit wait isn’t solving my issue. Thanks.

Answer 1

Remember that there is a difference between several scenarios:

• An element not being present at all in the DOM.
• An element being present in the DOM but not visible.
• An element being present in the DOM but not enabled. (i.e. clickable)

My guess is that if some of the page is being displayed with javascript, the elements are already present in the browser DOM, but are not visible. The implicit wait only waits for an element to appear in the DOM, so it returns immediately, but when you try to interact with the element you get a NoSuchElementException. You could test this hypothesis by writing a helper method that explicits waits for an element to be be visible or clickable.

Some examples (in Java):

public WebElement getWhenVisible(By locator, int timeout) {
    WebElement element = null;
    WebDriverWait wait = new WebDriverWait(driver, timeout);
    element = wait.until(ExpectedConditions.visibilityOfElementLocated(locator));
    return element;
}

public void clickWhenReady(By locator, int timeout) {
    WebDriverWait wait = new WebDriverWait(driver, timeout);
    WebElement element = wait.until(ExpectedConditions.elementToBeClickable(locator));
    element.click();
}