LDNSE #14 Mark Collin: All in Good Time

Mark Collin talking about Selenium Wait at London Selenium Meetup

Transcript

1. Mark Collin - @Ardesco http://ardesco.lazerycode.com All In Good Time 1
2. It’s a wait problem!
3. WebDriver Timeouts • Page load timeout • Script timeout • Implicitly wait
4. Implicit waits are evil! • They slow your checks down! • It’s not always obvious that they have been set. • They are left over baggage from Selenium 1
5. • Remember, when you set an implicit wait it lives for the life of the driver object. • Try to make it clear that you are setting implicit waits in your code. But I want to use them OK you can use them, but be careful!
6. So what should I use?
7. Explicit Waits! ! WebElement payButton = driver.findElement(By.id("pay_now"));
 WebDriverWait wait = new WebDriverWait(driver, 15, 500);
 wait.until(ExpectedConditions.visibilityOf(payButton)); There’s a pre-defined ExpectedConditions class in Java
8. Or maybe the Fluent Wait API (The core of Explicit Waits) • Predicates - Return a boolean • Functions - Return anything Wait<WebDriver> wait = new FluentWait<WebDriver>(driver)
 .withTimeout(15, TimeUnit.SECONDS)
 .pollingEvery(500, TimeUnit.MILLISECONDS)
 .ignoring(NoSuchElementException.class)
 .ignoring(StaleElementReferenceException.class)
 .withMessage("The message you will see in if a TimeoutException is thrown");
 
 wait.until(<Predicate> or <Function>)
9. What can I check for with Explicit/Fluent Waits? • Existence of elements • Visibility of elements • Invisibility of elements • Elements to stop/start moving • Alerts • Javascript hooks to be fired • Javascript values to be set • Pretty much anything!
10. Waiting anti-patterns.
11. public class WebElementLookup {
 private static final Logger LOG = LoggerFactory.getLogger(WebElementLookup.class);
 
 public static final int DEFAULT_TIMEOUT_IN_SECONDS = 10;
 private static final int POLL_INTERVAL_IN_MILLISECONDS = 300;
 
 private final By selector;
 private final int timeout;
 
 public WebElementLookup(final By selector, final int timeout) {
 this.selector = selector;
 this.timeout = timeout;
 }
 
 public WebElementLookup(final By selector) {
 this(selector, DEFAULT_TIMEOUT_IN_SECONDS);
 }
 
 public WebElement element(final WebDriver driver) {
 WebDriverWait wait = new WebDriverWait(driver, timeout, POLL_INTERVAL_IN_MILLISECONDS);
 return wait.until(new ExpectedCondition<WebElement>() {
 public WebElement apply(WebDriver driver) {
 LOG.debug("Looking up elements for selector {}", selector);
 final List<WebElement> elements = driver.findElements(selector);
 for (final WebElement webElement : elements) {
 if (matches(webElement)) {
 return webElement;
 }
 }
 return null;
 }
 });
 }
 
 private boolean matches(final WebElement webElement) {
 if (webElement == null) {
 return false;
 }
 return true;
 }
 } public WebElement findElement(final WebElementLookup webElementLookup) {
 return webElementLookup.element(driver);
 } public void clickBackLink() {
 driver.findElement(new WebElementLookup(By.className("back"))).click();
 }
12. Waiting anti-patterns. • Writing you own wait framework. • Mixing waiting strategies. • Waiting for a fixed period of time e.g. Thread.sleep()
13. It’s a wait problem!
14. It’s a wait problem! Maybe it’s a StaleElementReferenceException Problem…
15. So what is a StaleElementReferenceException?
16. How do we fix a StaleElementReferenceException?
17. So you can’t use waits with a StaleElementReferenceException?
18. Mark Collin - @Ardesco http://ardesco.lazerycode.com Questions?