1 files changed, 33 insertions, 0 deletions
diff --git a/testing/web-platform/tests/css/css-shadow-parts/support/shadow-helper.js b/testing/web-platform/tests/css/css-shadow-parts/support/shadow-helper.js
new file mode 100644
index 0000000000..94accd6b1f
--- /dev/null
+++ b/testing/web-platform/tests/css/css-shadow-parts/support/shadow-helper.js
@@ -0,0 +1,33 @@
+// Takes a root element and a list of ids of shadow host elements. Each id refers to a shadow host
+// inside the previous id's shadow tree.
+function getElementByShadowIds(root, ids) {
+  for (var i = 0; ;i++) {
+    var host = root.getElementById(ids[i]);
+    if (host == null) {
+      throw "No element found: i=" + i + " id=" + ids[i] + ". Root was " + root;
+    }
+    if (i == ids.length - 1) {
+      return host;
+    }
+    root = host.shadowRoot;
+    if (root == null) {
+      throw "No shadowRoot found: i=" + i + " id=" + ids[i] + ". Host was " + host;
+    }
+  }
+}
+
+// Installs a mininal custom element based on this template.
+function installCustomElement(element_name, template_id) {
+  ceClass = class extends HTMLElement {
+    constructor() {
+      super();
+      var template = document
+        .getElementById(template_id)
+        .content;
+      this
+        .attachShadow({mode: 'open'})
+        .appendChild(template.cloneNode(true));
+    }
+  };
+  window.customElements.define(element_name, ceClass);
+}