test(wtr): enable custom element registry tests

Author: wjhsf

packages/@lwc/integration-not-karma/configs/integration.js

@@ -9,9 +9,6 @@ export default {
         // FIXME: These tests are just symlinks to integration-karma for now so the git diff smaller
         'test/**/*.spec.js',
 
-        // Hacky nonsense highly tailored to Karma
-        '!test/custom-elements-registry/index.spec.js',
-
         // Logging mismatches
         '!test/component/LightningElement.addEventListener/index.spec.js',
 

packages/@lwc/integration-not-karma/test/custom-elements-registry/index.spec.js

@@ -18,13 +18,13 @@ async function getEngineCode() {
         ? ''
         : await getModuleCode('synthetic-shadow');
 
-    return `
+    return `(() => {
         globalThis.process = { env: { NODE_ENV: "production" } };
         globalThis.LWC = globalThis.exports = {};
         globalThis.lwcRuntimeFlags = ${JSON.stringify(lwcRuntimeFlags)};
         ${syntheticShadow};
         ${engineDom};
-        `;
+    })();`;
 }
 
 /**
@@ -157,7 +157,9 @@ describe('custom elements registry', () => {
 
             it(`creates elements in first engine - ${description}`, () => {
                 injectEngine();
-                callInIframe(() => (window.oldLWC = window.LWC));
+                callInIframe(() => {
+                    globalThis.oldLWC = globalThis.LWC;
+                });
                 injectEngine();
                 callInIframe(injectableCreateLWC, { customElement, globalLWC: 'oldLWC' });