docs: add forms overview example for snippets (#25663)

PR Close #25663

aio/content/examples/forms-overview/src/app/app.component.spec.ts

@@ -0,0 +1,31 @@
+import { TestBed, async } from '@angular/core/testing';
+import { AppComponent } from './app.component';
+import { TemplateModule } from './template/template.module';
+import { ReactiveModule } from './reactive/reactive.module';
+
+describe('AppComponent', () => {
+
+  beforeEach(async(() => {
+    TestBed.configureTestingModule({
+      imports: [ReactiveModule, TemplateModule],
+      declarations: [
+        AppComponent
+      ],
+    }).compileComponents();
+  }));
+
+  it('should create the app', async(() => {
+    const fixture = TestBed.createComponent(AppComponent);
+    const app = fixture.debugElement.componentInstance;
+
+    expect(app).toBeTruthy();
+  }));
+
+  it('should render title in a h1 tag', async(() => {
+    const fixture = TestBed.createComponent(AppComponent);
+    fixture.detectChanges();
+
+    const compiled = fixture.debugElement.nativeElement;
+    expect(compiled.querySelector('h1').textContent).toContain('Forms Overview');
+  }));
+});