chromium/third_party/blink/web_tests/accessibility/img-srcset-1x.html

<!DOCTYPE html>

<script>
    testRunner.setBackingScaleFactor(1, () => {});
</script>

<script src="../resources/testharness.js"></script>
<script src="../resources/testharnessreport.js"></script>

<img id="img1" src="resources/cake.png">
<img id="img2" width=16 height=16 srcset="resources/red.png 1x, resources/green.png 2x">

<script>
function filename(url) {
    return url.substring(url.lastIndexOf('/') + 1);
}

test(function(t) {
    var axImg1 = accessibilityController.accessibleElementById("img1");
    assert_equals(filename(axImg1.url), 'cake.png');
    var axImg2 = accessibilityController.accessibleElementById("img2");
    assert_equals(filename(axImg2.url), 'red.png');
}, "Test that img.url retrieves the loaded image when the img uses srcset");
</script>