chromium/third_party/blink/web_tests/fast/scroll-behavior/parse-scroll-behavior.html

<!DOCTYPE html>
<html>
<head>
<style>
#scrollBehaviorAuto {
    scroll-behavior: auto;
}

#scrollBehaviorSmooth {
    scroll-behavior: smooth;
}
</style>
<script src="../../resources/js-test.js"></script>
</head>
<body>
<div id="scrollBehaviorAuto"></div>
<div id="scrollBehaviorSmooth"></div>
<script>
description('Test that setting and getting scroll-behavior works as expected');

debug("Test getting scroll-behavior set through CSS");
var scrollBehaviorAuto = document.getElementById("scrollBehaviorAuto");
shouldBe("getComputedStyle(scrollBehaviorAuto, '').getPropertyValue('scroll-behavior')", "'auto'");

var scrollBehaviorSmooth = document.getElementById("scrollBehaviorSmooth");
shouldBe("getComputedStyle(scrollBehaviorSmooth, '').getPropertyValue('scroll-behavior')", "'smooth'");

debug("");
debug("Test initial value of scroll-behavior");
var element = document.createElement("div");
document.body.appendChild(element);
shouldBe("getComputedStyle(element, '').getPropertyValue('scroll-behavior')", "'auto'");

debug("");
debug("Test getting and setting scroll-behavior through JS");
element = document.createElement("div");
document.body.appendChild(element);
element.style.scrollBehavior = "smooth";
shouldBe("getComputedStyle(element, '').getPropertyValue('scroll-behavior')", "'smooth'");

element.style.scrollBehavior = "auto";
shouldBe("getComputedStyle(element, '').getPropertyValue('scroll-behavior')", "'auto'");

debug("");
debug("Test the value 'initial'");
element.style.scrollBehavior = "smooth";
shouldBe("getComputedStyle(element, '').getPropertyValue('scroll-behavior')", "'smooth'");
element.style.scrollBehavior = "initial";
shouldBe("getComputedStyle(element, '').getPropertyValue('scroll-behavior')", "'auto'");

debug("");
debug("Test the value 'inherit'");
var parentElement = document.createElement("div");
document.body.appendChild(parentElement);
parentElement.style.scrollBehavior = "smooth";
shouldBe("getComputedStyle(parentElement, '').getPropertyValue('scroll-behavior')", "'smooth'");
element = document.createElement("div");
parentElement.appendChild(element);
element.style.scrollBehavior = "inherit";
shouldBe("getComputedStyle(element, '').getPropertyValue('scroll-behavior')", "'smooth'");

debug("");
debug("Test that scroll-behavior is not inherited by default");
var parentElement = document.createElement("div");
document.body.appendChild(parentElement);
parentElement.style.scrollBehavior = "smooth";
shouldBe("getComputedStyle(parentElement, '').getPropertyValue('scroll-behavior')", "'smooth'");
element = document.createElement("div");
parentElement.appendChild(element);
shouldBe("getComputedStyle(element, '').getPropertyValue('scroll-behavior')", "'auto'");
</script>
</body>
</html>