Test Automation Challenges

Scroll-Driven Animations and Test Automation

6 min read • 1,194 words

For years, web developers and QA engineers have played a game of cat and mouse with the browser. We’ve spent years optimizing test automation to handle the asynchronous nature of the web, reaching a “well-oiled” state of stability. Now, a new challenger has entered the ring: Scroll-Driven Animations (SDA).

The Era of “Wait and See”

Traditionally, test automation tools (like Playwright, Cypress, or Selenium) have become incredibly smart at waiting. They don’t just “sleep”, they check for:

• Page Load States: Ensuring the network is idle.
• Element Visibility: Checking if a button is not just in the DOM, but clickable.
• Animation Stabilization: Waiting for a brief period so a 300ms fade-in doesn’t cause a “flaky” screenshot.

In this world, animations were transient. They had a beginning, a middle, and an end. If you waited half a second, the UI would reach its “final form,” making it safe to test.

The same is true for automated accessibility tests, which usually wait for the page to be in a stable state to accurately assess contrast ratios, focus states, and other accessibility features.

Enter the Scroll: Why SDA Changes the Game

Scroll-driven animations break the “final form” rule. Unlike classic CSS transitions that trigger and finish, an SDA’s state is bound directly to the scroll progress.

The problem? There is no longer a “finished” state to wait for. The element is effectively always in the middle of a transition as long as the user (or the test runner) is moving.

The Visual Testing Trap

If you are performing visual regression testing or worse accessibility testing, SDA creates a high risk of “flakiness.” Depending on the exact pixel-position of the scroll container when the screenshot is snapped, an element might be 20% opaque or 80% opaque.

Here’s this in action (if your browser supports it):

Notice how the text opacity changes as you scroll—this inconsistent state is exactly what breaks automated testing.

For automated accessibility tests, this is a nightmare. If a test runner checks the text while it’s mid-fade, the “baseline” image will never consistently match the “current” image.

Accessibility Testing

The friction isn’t just visual; it’s functional. Automated accessibility tools like axe-core are designed to catch contrast violations.

If your test scrolls to a section to check for compliance, and that section uses an SDA to fade text in, the tool might catch the text while it’s at 30% opacity.

Scroll-Triggered vs. Scroll-Driven

Scroll-triggered animations represent the next evolution of scroll-based animations arriving in 2026. It’s important to distinguish between the two, as they require different testing strategies:

Considering the differences, scroll-triggered animations pose less of a problem for test automation, as they can be handled with traditional waiting strategies. Scroll-driven animations, however, require a more nuanced approach to ensure reliable testing outcomes.

Want to go deeper on the UX rationale (not tooling) and why scroll-driven behavior can be a better fit for subtle fades like this example? Check out Brecht De Ruyte’s post on CSS animation triggers.

How do we adapt? (It’s complicated)

There is no “magic button” in current automation frameworks to handle SDA globally. Because these animations are tied to the scroll timeline rather than a clock, our usual tricks for “waiting” fall short. Here is a breakdown of current strategies and why they aren’t perfect:

Forcing prefers-reduced-motion

Setting prefers-reduced-motion is the standard “go-to” for automation. By setting the browser’s emulation to reduced, many CSS animations are stripped away.

The Future: prefers-reduced-transparency as a Better Solution

Ideally for those fading use cases, we’d use prefers-reduced-transparency, but browser support isn’t mature enough to make this a reliable universal fix yet, nor is it possible to set this setting in most testing tools yet.

Manual Scroll Mocking (E2E Only)

For functional E2E tests, you can force the browser to a specific pixel value:

// Force Playwright to scroll to specific position before taking screenshot
// (Note: This is rarely precise enough for reliable testing)
await page.evaluate(() => window.scrollTo(0, 500));

Linearizing or Disabling Timelines (The Technical Hack)

The third option involves using a “test-only” stylesheet or attribute injection to override the scroll-timeline. This would essentially turn off problematic animations during test automation.

The How

You could inject CSS that overwrites the animation-timeline by setting animation-timeline: none !important;, forcing the element to its final state (e.g., opacity: 1).

Alternatively, you could set a data-a11y-testing attribute on the body and use that as a selector to disable animations in your stylesheet:

body:not([data-a11y-testing]) .animated-element {
	animation: fadeIn 1ms linear both;
	animation-timeline: view();
}

The Missing Feature: A “Global SDA Toggle”

The ideal solution doesn’t actually exist yet. We need a native browser setting or a flag in the Chrome DevTools Protocol (CDP) that allows automation runners to “freeze” or “disable” scroll-linked timelines, forcing all elements to their 100% animation state.

Until then, we’re stuck choosing between flaky visual tests or heavy-handed CSS overrides that might mask real-world issues.

What’s Your Experience?

As SDA becomes more prevalent, this friction is only going to increase. I’m curious if anyone has found a more elegant way to handle this without compromising the integrity of the test environment.

• Are you using specific Playwright/Cypress configurations to handle this?

• Have you found a way to bridge the gap for a11y scanners like axe-core?

Let’s talk about it! Reach out to me on Bluesky or LinkedIn if you have a working solution or a horror story to share.