How to Test for a Broken Image in Cypress

Описание: A comprehensive guide on how to test for broken images in Cypress, including checking image visibility and verifying alt text using the naturalWidth property.
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This video is based on the question https://stackoverflow.com/q/73604180/ asked by the user 'Jason Scaggs' ( https://stackoverflow.com/u/19867290/ ) and on the answer https://stackoverflow.com/a/73604196/ provided by the user 'Fody' ( https://stackoverflow.com/u/16997707/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Test for a Broken Image in Cypress

When developing web applications, ensuring that all images load correctly is crucial for user experience. A broken image can be frustrating and may even degrade the overall perception of your site. If you're using Cypress for automated testing, you might wonder how to effectively test for broken images. In this guide, we’ll explore a straightforward solution to this problem.

The Challenge

You may have come across a situation where you're trying to verify if an image on your webpage is broken. The HTML structure of a broken image could look like this:

[[See Video to Reveal this Text or Code Snippet]]

In this scenario, you might attempt to access the alternative text (alt text) of the image using Cypress commands:

[[See Video to Reveal this Text or Code Snippet]]

However, this approach can fail since the # shadow-root element is inaccessible from JavaScript and cannot be queried directly with Cypress.

The Solution

Don’t fret! While direct access to shadow DOM elements may not be possible, there’s still a way to verify whether the image is broken. The most reliable method involves checking the image's naturalWidth property. If the image is loaded properly, this property will return a value greater than zero.

Steps to Verify a Broken Image

Here’s how you can do it:

Select the Image: Utilize the cy.get() command to fetch the image element based on its src attribute.

Check Visibility: Use the .should('be.visible') assertion to ensure that Cypress can see the image element.

Assess Natural Width: Finally, use the .and() function with a custom assertion to check if the naturalWidth of the image is greater than zero.

Example Code

Here’s how this entire process is implemented in Cypress:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

cy.get('img[src="..."]'): This command retrieves the image you want to check by its source URL.

.should('be.visible'): This assertion ensures that the image is actually rendered on the page.

.and($img => expect($img[0].naturalWidth).to.be.gt(0)): This function checks the naturalWidth property of the image. If it is greater than zero, the image is successfully loaded and not broken.

Conclusion

By following these steps, you can effectively test for broken images in your web applications using Cypress. Although it may seem challenging to access certain elements, leveraging the naturalWidth property provides a solid workaround. Ensuring that your images are not broken is essential for maintaining a quality user experience. Happy testing!