angularjs - How to unit test if an angular 2 component contains another component -

i'm quite new angular 2.

i have component in turn has other components in template.

how write unit tests check if parent component consists of other components.

mentioning sample or directing me resource helpful.

mycomponent.ts:

import { component } '@angular/core'; @component({ selector: 'my-component', templateurl: `<div> <other-component></other-component> </div>` }) export class mycomponent{  } 

othercomponent.ts:

import { component } '@angular/core'; @component({ selector: 'other-component', templateurl: `<div> <h1>other component</h1> </div>` }) export class othercomponent{  } 

to test if component, when compiled, contains other components:

• inject component you're testing
• inject child components
• create parent component
• detect changes
• use queryselector or queryselectorall find child components

i typically check element exists , further testing in spec individual child component.

import { testbed, async } '@angular/core/testing';  import { appcomponent } './app.component'; import { othercomponent } './other/other.component';  describe('appcomponent', () => {   beforeeach(async(() => {     testbed.configuretestingmodule({       declarations: [         appcomponent,         othercomponent       ],     }).compilecomponents();   }));    it('should create app', async(() => {     const fixture = testbed.createcomponent(appcomponent);     const app = fixture.debugelement.componentinstance;     expect(app).tobetruthy();   }));    it('should have other component', async(() => {     const fixture = testbed.createcomponent(appcomponent);     fixture.detectchanges();     const compiled = fixture.debugelement.nativeelement;     expect(compiled.queryselector('app-other')).not.tobe(null);   })); }); 

checking null queryselector determine if component exists. queryselector mdn:

returns null if no matches found; otherwise, returns first matching element.

---

if you'd check there multiple instances of same child component, can use queryselectorall , check length property:

expect(compiled.queryselectorall('app-other').length).tobegreaterthan(4);