1 files changed, 72 insertions, 0 deletions
diff --git a/testing/web-platform/tests/html/rendering/bidi-rendering/slot-direction.window.js b/testing/web-platform/tests/html/rendering/bidi-rendering/slot-direction.window.js
new file mode 100644
index 0000000000..673f6c0b0f
--- /dev/null
+++ b/testing/web-platform/tests/html/rendering/bidi-rendering/slot-direction.window.js
@@ -0,0 +1,72 @@
+// https://html.spec.whatwg.org/multipage/rendering.html#bidi-rendering
+// https://github.com/whatwg/html/pull/9796
+// https://github.com/whatwg/html/pull/9880
+
+for (let t of [
+  {
+    description: "<slot> inherits direction from parent",
+    shadow_tree: `
+      <div dir=ltr data-expected="ltr">
+        <slot data-expected="ltr"></slot>
+      </div>
+    `,
+    host_dir: "rtl",
+  },
+  {
+    description: "<slot> inherits CSS direction from parent",
+    shadow_tree: `
+      <div style="direction: ltr" data-expected="ltr">
+        <slot data-expected="ltr"></slot>
+      </div>
+    `,
+    host_dir: "rtl",
+  },
+  {
+    description: "<slot dir=ltr>",
+    shadow_tree: `
+      <slot dir="ltr" data-expected="ltr"></slot>
+    `,
+    host_dir: "rtl",
+  },
+  {
+    description: "<slot dir=rtl>",
+    shadow_tree: `
+      <slot dir="rtl" data-expected="rtl"></slot>
+    `,
+    host_dir: "ltr",
+  },
+  {
+    description: "<slot dir=auto> resolving to LTR",
+    shadow_tree: `
+      <slot dir="ltr" data-expected="ltr"></slot>
+    `,
+    host_dir: "rtl",
+    host_contents: "A",
+  },
+  {
+    description: "<slot dir=auto> resolving to RTL",
+    shadow_tree: `
+      <slot dir="rtl" data-expected="rtl"></slot>
+    `,
+    host_dir: "ltr",
+    host_contents: "\u0627",
+  },
+]) {
+  test(() => {
+    let host = document.createElement("div");
+    document.body.appendChild(host);
+    host.dir = t.host_dir;
+    if ("host_contents" in t) {
+      host.innerHTML = t.host_contents;
+    }
+
+    let root = host.attachShadow({mode: "open"});
+    root.innerHTML = t.shadow_tree;
+
+    for (let e of Array.from(root.querySelectorAll("[data-expected]"))) {
+      assert_equals(getComputedStyle(e).direction, e.getAttribute("data-expected"), `direction of ${e.nodeName}`);
+    }
+
+    host.remove();
+  }, `<slot> element sets CSS direction property: ${t.description}`);
+}