test(elements): add basic integration test for angular elements (#24861)

PR Close #24861

integration/ng_elements/src/app.ts

@@ -0,0 +1,33 @@
+import {HelloWorldComponent, HelloWorldShadowComponent, TestCardComponent} from './elements';
+
+import {NgModule, Injector} from '@angular/core';
+import {BrowserModule} from '@angular/platform-browser';
+import {createCustomElement} from '@angular/elements';
+
+
+@NgModule({
+  declarations: [HelloWorldComponent, HelloWorldShadowComponent, TestCardComponent],
+  entryComponents: [HelloWorldComponent, HelloWorldShadowComponent, TestCardComponent],
+  imports: [BrowserModule],
+})
+export class AppModule {
+  constructor(private injector:Injector){
+    customElements.define(
+      'hello-world-el',
+      createCustomElement(HelloWorldComponent, {injector})
+    );
+    customElements.define(
+      'hello-world-shadow-el',
+      createCustomElement(HelloWorldShadowComponent, {injector})
+    );
+    customElements.define(
+      'test-card',
+      createCustomElement(HelloWorldShadowComponent, {injector})
+    );
+  }
+  ngDoBootstrap(){
+
+  }
+}
+
+export {HelloWorldComponent};