LayoutTests/accessibility/custom-elements/controls-shadow.html

<!DOCTYPE html>
<html>
<body>
<script src="../../resources/js-test.js"></script>
<script src="../../resources/accessibility-helper.js"></script>
<div class="control">Panel 1</div>
<div class="control">Panel 2</div>
<div id="host"></div>
<script>

class CustomTabElement extends HTMLElement {
    constructor()
    {
        super();
        window.internals = this.attachInternals();
        internals.role = 'tab';
        internals.ariaControlsElements = Array.from(document.querySelectorAll('.control'));
        shouldBe('internals.ariaControlsElements.length', '2');
        shouldBe('internals.ariaControlsElements[0]', 'document.querySelectorAll(".control")[0]');
        shouldBe('internals.ariaControlsElements[1]', 'document.querySelectorAll(".control")[1]');
    }
};
customElements.define('custom-tab', CustomTabElement);

const customElement = new CustomTabElement;
customElement.id = 'custom-tab';
const shadowRoot = host.attachShadow({'mode': 'closed'});
shadowRoot.appendChild(customElement);

description("This tests that ElementInternals.ariaControlsElements can reference nodes outside the shadow tree.");
if (!window.accessibilityController)
    debug('This test requires accessibilityController');
else {
    function labelForControl(control) {
        if (accessibilityController.platformName == "mac")
            return control.childAtIndex(0).stringValue;
        return control.stringValue;
    }
    window.customTab = accessibilityController.accessibleElementById('custom-tab');
    shouldBeEqualToString('labelForControl(customTab.ariaControlsElementAtIndex(0))', 'AXValue: Panel 1');
    shouldBeEqualToString('labelForControl(customTab.ariaControlsElementAtIndex(1))', 'AXValue: Panel 2');
}

</script>
</body>
</html>