diff --git a/testing/web-platform/tests/html/dom/elements/global-attributes/dir-slots-directionality.tentative.html b/testing/web-platform/tests/html/dom/elements/global-attributes/dir-slots-directionality.tentative.html
index 1f0dc07f8ef5c..5e8cedb9c156f 100644
--- a/testing/web-platform/tests/html/dom/elements/global-attributes/dir-slots-directionality.tentative.html
+++ b/testing/web-platform/tests/html/dom/elements/global-attributes/dir-slots-directionality.tentative.html
@@ -2,9 +2,9 @@
 <title>HTML Test: dir=auto|rtl with slots, and direction should be RTL</title>
 <meta charset="UTF-8">
 <meta name="author" title="Miyoung Shin" href="mailto:myid.shin@igalia.com">
-<meta name="assert" content="When dir='auto', the direction is set according to
-  slot's assigned node. And the direction should be propagated to shadow" />
+<meta name="author" title="L. David Baron" href="mailto:dbaron@chromium.org">
 <link rel="help" href="https://html.spec.whatwg.org/multipage/#the-dir-attribute"/>
+<link rel="help" href="https://github.com/whatwg/html/issues/3699">
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
 <div id="host1"><span></span></div>
@@ -12,27 +12,55 @@
 <span id="host3" dir="auto"></span>
 <div id="host4">اختبر</div>
 <div id="host5"></div>
+<div id="host6">اختبر</div>
 <script>
-let root1 = host1.attachShadow({mode:"open"});
-root1.innerHTML = '<slot dir="rtl"></slot>';
 
-let root2 = host2.attachShadow({mode:"open"});
-root2.innerHTML = '<span></span>';
+test(() => {
+  let root1 = host1.attachShadow({mode:"open"});
+  root1.innerHTML = '<slot dir="rtl"></slot>';
+  let span = host1.firstChild;
+  assert_equals(getComputedStyle(span).direction, "rtl");
+  assert_true(span.matches(":dir(ltr)"));
+}, 'Slots: Directionality: dir=rtl on slot');
 
-let root3 = host3.attachShadow({mode:"open"});
-root3.innerHTML = `اختبر`;
+test(() => {
+  let root2 = host2.attachShadow({mode:"open"});
+  root2.innerHTML = '<span></span>';
+  let span = root2.querySelector("span");
+  assert_equals(getComputedStyle(span).direction, "rtl");
+  assert_true(span.matches(":dir(rtl)"));
+}, 'Slots: Directionality: dir=rtl on host');
 
-let root4 = host4.attachShadow({mode:"open"});
-root4.innerHTML = '<span dir="auto"><slot></slot></span>';
+test(() => {
+  let root3 = host3.attachShadow({mode:"open"});
+  root3.innerHTML = `اختبر`;
+  let span = host3;
+  assert_equals(getComputedStyle(span).direction, "ltr");
+  assert_true(span.matches(":dir(ltr)"));
+}, 'Slots: Directionality: dir=auto on host with Arabic shadow tree content');
 
-let root5 = host5.attachShadow({mode:"open"});
+test(() => {
+  let root4 = host4.attachShadow({mode:"open"});
+  root4.innerHTML = '<span dir="auto"><slot></slot></span>';
+  let span = root4.querySelector("span");
+  assert_equals(getComputedStyle(span).direction, "ltr");
+  assert_true(span.matches(":dir(ltr)"));
+}, 'Slots: Directionality: dir=auto in shadow tree with Arabic light tree content');
+
+test(() => {
+  let root5 = host5.attachShadow({mode:"open"});
   root5.innerHTML = '<span dir="auto"><slot>اختبر</slot></span>';
+  let span = root5.querySelector("span");
+  assert_equals(getComputedStyle(span).direction, "rtl");
+  assert_true(span.matches(":dir(rtl)"));
+}, 'Slots: Directionality: dir=auto in shadow tree with Arabic shadow tree content');
 
 test(() => {
-  assert_equals(getComputedStyle(host1.firstChild).direction, "rtl");
-  assert_equals(getComputedStyle(root2.querySelector("span")).direction, "rtl");
-  assert_equals(getComputedStyle(host3).direction, "ltr");
-  assert_equals(getComputedStyle(root4.querySelector("span")).direction, "rtl");
-  assert_equals(getComputedStyle(root5.querySelector("span")).direction, "rtl");
-}, 'Slots: Directionality');
+  let root6 = host6.attachShadow({mode:"open"});
+  root6.innerHTML = '<slot dir="auto"></slot>';
+  let span = root6.querySelector("slot");
+  assert_equals(getComputedStyle(span).direction, "rtl");
+  assert_true(span.matches(":dir(rtl)"));
+}, 'Slots: Directionality: dir=auto on slot with Arabic light tree content');
+
 </script>