feat(aio): add google analytics (#15081)

aio/src/app/app.component.spec.ts

@@ -2,6 +2,7 @@ import { async, inject, ComponentFixture, TestBed } from '@angular/core/testing'
 import { APP_BASE_HREF } from '@angular/common';
 import { AppComponent } from './app.component';
 import { AppModule } from './app.module';
+import { GaService } from 'app/shared/ga.service';
 import { SearchService } from 'app/search/search.service';
 import { MockSearchService } from 'testing/search.service';
 
@@ -14,7 +15,8 @@ describe('AppComponent', () => {
       imports: [ AppModule ],
       providers: [
         { provide: APP_BASE_HREF, useValue: '/' },
-        { provide: SearchService, useClass: MockSearchService }
+        { provide: SearchService, useClass: MockSearchService },
+        { provide: GaService, useClass: TestGaService }
       ]
     });
     TestBed.compileComponents();
@@ -29,6 +31,18 @@ describe('AppComponent', () => {
     expect(component).toBeDefined();
   });
 
+  describe('google analytics', () => {
+    it('should call gaService.locationChanged with initial URL', () => {
+      const url = window.location.pathname.substr(1); // strip leading '/'
+      const { locationChanged } = TestBed.get(GaService) as TestGaService;
+      expect(locationChanged.calls.count()).toBe(1, 'gaService.locationChanged');
+      const args = locationChanged.calls.first().args;
+      expect(args[0]).toBe(url);
+    });
+
+    // Todo: add test to confirm tracking URL when navigate.
+  });
+
   describe('isHamburgerVisible', () => {
   });
 
@@ -57,3 +71,7 @@ describe('AppComponent', () => {
     }));
   });
 });
+
+class TestGaService {
+  locationChanged = jasmine.createSpy('locationChanged');
+}