Selenium: Check for the presence of element

In real-time automation, do we check for the presence of every element(in test) before performing some action on them?

Wherever there is a findElement statement, there is a chance of NoSuchElementException. My question is whether we check for the presence of the element everytime?

Does every findElement statement need to be surrounded by try-catch block?

Solution 1:

There are two cases to account for:

1. Is the element present; meaning does it exist in the DOM.
2. Is the element visible; meaning it is in DOM and does not have a hidden or equivalent flag.

For the first case, I use the following helper method:

this.waitForElement = function(locator) {
    browser.wait(function() {
      return browser.isElementPresent(locator);
    }, testData.Timeout.TWO_MINUTES);
};

This will wait for an arbitrary amount of time for the element matching the provided locator to become present (It exists in the DOM).

For the second case, I use this helper method:

this.waitForElementIsVisible = function(el){
    let EC = protractor.ExpectedConditions;
    browser.wait(EC.visibilityOf(el), testData.Timeout.TWO_MINUTES, "Element did not become visible after 2 minutes");
};

This takes a WebElement as the single parameter and waits until the element becomes visible (It exists in the DOM and is not hidden via a css style or something)

As a bonus, I also found this helper method to be useful for testing error states in a form:

this.waitForElementIsClickable = function(el){
    let EC = protractor.ExpectedConditions;
    browser.wait(EC.elementToBeClickable(el), testData.Timeout.TWO_MINUTES, "Element did not become clickable after 2 minutes");
};

Takes a WebElement as the first parameter and waits until that WebElement can be clicked.

Note, I am using protractor, and reference Protractor in these snippets. So unless you are using Protractor as well, it's likely these will not work 100% through a straight copy+paste. Should be easy enough to tweak them to suite your setup though.

Solution 2:

Answering your questions one by one:

• "In real-time automation, do we check for the presence of every element(in test) before performing some action on them" : Yes as per best practices whenever user is redirected to a new page you need to ensure the state of the element as per your desired action.

There are 3 most widely used ExpectedConditions which can be used in-conjuction with WebDriverWait to validate an element's state as follows:

presenceOfElementLocated

presenceOfElementLocated(By locator) is defined as follows :

public static ExpectedCondition<WebElement> presenceOfElementLocated(By locator)

Description : An expectation for checking that an element is present on the DOM of a page. This does not necessarily mean that the element is visible.

visibilityOfElementLocated

visibilityOfElementLocated(By locator) is defined as follows :

public static ExpectedCondition<WebElement> visibilityOfElementLocated(By locator)

Description : An expectation for checking that an element is present on the DOM of a page and visible. Visibility means that the element is not only displayed but also has a height and width that is greater than 0.

elementToBeClickable

elementToBeClickable(By locator) is defined as follows :

public static ExpectedCondition<WebElement> elementToBeClickable(By locator)

Description : An expectation for checking an element is visible and enabled such that you can click it.

• "Wherever there is a findElement statement, there is a chance of NoSuchElementException": No, not at all. If you construct a proper Locator Strategy, you won't face NoSuchElementException.

Here you will find a detailed discussion on NoSuchElementExeption, selenium unable to locate element

• Does every findElement statement need to be surrounded by try-catch block: No, not always. If your usecase involves handling of both affirmative and negative scenarios then try-catch {} block is perfecto.