css/cssom-view/scrollIntoView-horizontal-partially-visible.html

<!doctype html>
<title>CSSOM View - scrollIntoView scrolls partially-visible element in both inline and block directions.</title>
<meta charset="utf-8">
<link rel="author" title="Emilio Cobos Álvarez" href="mailto:emilio@crisal.io">
<link rel="author" title="Mozilla" href="https://mozilla.org">
<link rel="help" href="https://drafts.csswg.org/cssom-view/#dom-element-scrollintoview">
<link rel="help" href="https://bugs.webkit.org/show_bug.cgi?id=203497">
<link rel="help" href="https://bugs.chromium.org/p/chromium/issues/detail?id=916631">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
  #scroller {
    width: 200px;
    height: 200px;
    padding-top: 200px;
    padding-left: 200px;
    background: purple;
    overflow: hidden;
  }
  #child {
    width: 400px;
    height: 400px;
    background: green;
  }
</style>
<div id="scroller">
  <div id="child"></div>
</div>
<script>
  test(function() {
    let scroller = document.getElementById("scroller");
    let child = document.getElementById("child");

    scroller.scrollTop = 0;
    scroller.scrollLeft = 0;

    assert_equals(scroller.scrollTop, 0, "Precondition");
    assert_equals(scroller.scrollLeft, 0, "Precondition");
    assert_not_equals(scroller.scrollTopMax, 0, "Precondition")
    assert_not_equals(scroller.scrollLeftMax, 0, "Precondition")

    child.scrollIntoView();

    assert_equals(scroller.scrollTop, 200, "Should have scrolled in the block direction");
    assert_equals(scroller.scrollLeft, 200, "Should have scrolled in the inline direction");
  }, "scrollIntoView scrolls partially-visible child in both axes");
</script>