fixup

Author: JakobVogelsang

web-test-runner.config.mjs

@@ -132,8 +132,21 @@ export default /** @type {import("@web/test-runner").TestRunnerConfig} */ ({
   
   }
   </script>
+  <script>
+  const _customElementsDefine = window.customElements.define;
+  window.customElements.define = (name, cl, conf) => {
+    if (!customElements.get(name)) {
+      try {
+        _customElementsDefine.call(window.customElements, name, cl, conf);
+      } catch (e) {
+        console.warn(e);
+      }
+    }
+  };
+</script>
             <script>window.process = { env: ${JSON.stringify(process.env)} }</script>
             <script type="module" src="${testFramework}"></script>
+            
             <script>
             function descendants(parent) {
               return (Array.from(parent.childNodes)).concat(