Selenium assertFalse fails with staleelementreferenceexception

问题

I have a selenium test in Java and I am doing some assertions like that:

assertFalse(isElementPresent(By.xpath("//td[2]/div")));

private boolean isElementPresent(By by) {
try { driver.findElement(by); return true; }
catch (NoSuchElementException e) { 
return false; }

It´s the standard method Selenium is generating when export from IDE to Java Webdriver.

(Yes I want to assert that this element is not present)

I always get errors when I am testing at this above code line Error: stale element reference: element is not attached to the DOM

But when I put a thread.sleep in front of that step it works. The fact I don´t get is that it is enough to wait 1 milli sec. Is it typical to wait before an assertion? Is there another way to solve this? (Implicit wait is not helping here) Greetings from Germany!

回答1:

As you are facing staleelementreferenceexception in assertFalse() function, to negate the FalsePossitive usecase you can induce WebDriverWait with ExpectedConditions clause set to stalenessOf within assertTrue() function as follows :

Assert.assertTrue(new WebDriverWait(driver, 20).until(ExpectedConditions.stalenessOf(driver.findElement(By.xpath("//td[2]/div")))));

Explaination

The ExpectedConditions clause stalenessOf will check for the staleness of the element identified as (By.xpath("//td[2]/div")). When the intended element becomes stale, you can check for assertTrue(boolean condition). assertTrue() would assert that a condition is true. If it isn't, an AssertionError would be raised.

assertFalse(condition)

If you still want to implement the FalsePossitive case of assertFalse(condition) raising Error you still can :

Assert.assertFalse(new WebDriverWait(driver, 20).until(ExpectedConditions.stalenessOf(driver.findElement(By.xpath("//td[2]/div")))));

回答2:

I think, timeouts are not set to WebDriver. try this

assertFalse(isElementPresent(By.xpath("//td[2]/div")));

private boolean isElementPresent(By by) {
driver.timeouts().implicitlyWait(5, TimeUnit.SECONDS);
driver.manage().timeouts().pageLoadTimeout(30, TimeUnit.SECONDS);
try { driver.findElement(by); return true; }
catch (NoSuchElementException e) { 
return false; }

来源：https://stackoverflow.com/questions/49231669/selenium-assertfalse-fails-with-staleelementreferenceexception