Testing Angular 2 components with Input properties provided

Question

Testing Angular 2 components with Input properties provided

Currently, I am working on a component that utilizes the @Input() annotation on an instance variable. As part of this process, I am attempting to write a unit test for the openProductPage() method. However, I'm feeling a bit uncertain about how to set up my unit test effectively. Although I could make the instance variable public, I believe there should be a better solution.

Can someone provide guidance on how to configure my Jasmine test so that a mocked product is injected or provided? My ultimate goal is to test the functionality of the openProductPage() method.

Here's a snippet of my component:

import {Component, Input} from "angular2/core";
import {Router} from "angular2/router";

import {Product} from "../models/Product";

@Component({
    selector: "product-thumbnail",
    templateUrl: "app/components/product-thumbnail/product-thumbnail.html"
})

export class ProductThumbnail {
    @Input() private product: Product;


    constructor(private router: Router) {
    }

    public openProductPage() {
        let id: string = this.product.id;
        this.router.navigate(["ProductPage", {id: id}]);
    }
}

angular typescript unit-testing jasmine angular-test

Answer 1

Answer №1

Referencing the official documentation found at https://angular.io/docs/ts/latest/guide/testing.html#!#component-fixture, one can create a new input object named expectedHero and then pass it to the component using comp.hero = expectedHero.

It is important to remember to call fixture.detectChanges(); in the end, as without it, the property will not be properly bound to the component.

Here is a working example:

// Setting up async beforeEach
beforeEach( async(() => {
    TestBed.configureTestingModule({
        declarations: [ DashboardHeroComponent ],
    })
    .compileComponents(); // Compiling template and CSS
}));

// Setting up synchronous beforeEach
beforeEach(() => {
    fixture = TestBed.createComponent(DashboardHeroComponent);
    comp    = fixture.componentInstance;
    heroEl  = fixture.debugElement.query(By.css('.hero')); // Finding the hero element

    // Simulating connection to an entity that supplies a hero
    expectedHero = new Hero(42, 'Test Name');
    comp.hero = expectedHero;
    fixture.detectChanges(); // Triggering initial data binding
});

Answer 2

Referencing the official documentation found at https://angular.io/docs/ts/latest/guide/testing.html#!#component-fixture, one can create a new input object named expectedHero and then pass it to the component using comp.hero = expectedHero.

It is important to remember to call fixture.detectChanges(); in the end, as without it, the property will not be properly bound to the component.

Here is a working example:

// Setting up async beforeEach
beforeEach( async(() => {
    TestBed.configureTestingModule({
        declarations: [ DashboardHeroComponent ],
    })
    .compileComponents(); // Compiling template and CSS
}));

// Setting up synchronous beforeEach
beforeEach(() => {
    fixture = TestBed.createComponent(DashboardHeroComponent);
    comp    = fixture.componentInstance;
    heroEl  = fixture.debugElement.query(By.css('.hero')); // Finding the hero element

    // Simulating connection to an entity that supplies a hero
    expectedHero = new Hero(42, 'Test Name');
    comp.hero = expectedHero;
    fixture.detectChanges(); // Triggering initial data binding
});

Answer 3

Answer №2

When utilizing TestBed.configureTestingModule for compiling your test component, consider this alternative method. It closely resembles the accepted solution but aligns more with how angular-cli typically generates specs. Just an additional perspective.

import { Component, CUSTOM_ELEMENTS_SCHEMA } from '@angular/core';
import { ComponentFixture, TestBed } from '@angular/core/testing';
import { DebugElement } from '@angular/core';

describe('ProductThumbnail', () => {
  let component: ProductThumbnail;
  let fixture: ComponentFixture<TestComponentWrapper>;

  beforeEach(async () => {
    await TestBed.configureTestingModule({
      declarations: [ 
        TestComponentWrapper,
        ProductThumbnail
      ],
      schemas: [CUSTOM_ELEMENTS_SCHEMA]
    })
    .compileComponents();

    fixture = TestBed.createComponent(TestComponentWrapper);
    component = fixture.debugElement.children[0].componentInstance;
    fixture.detectChanges();
  });

  it('should create', () => {
    expect(component).toBeTruthy();
  });
});

@Component({
  selector: 'test-component-wrapper',
  template: '<product-thumbnail [product]="product"></product-thumbnail>'
})
class TestComponentWrapper {
  product = new Product()
}

Answer 4

When utilizing TestBed.configureTestingModule for compiling your test component, consider this alternative method. It closely resembles the accepted solution but aligns more with how angular-cli typically generates specs. Just an additional perspective.

import { Component, CUSTOM_ELEMENTS_SCHEMA } from '@angular/core';
import { ComponentFixture, TestBed } from '@angular/core/testing';
import { DebugElement } from '@angular/core';

describe('ProductThumbnail', () => {
  let component: ProductThumbnail;
  let fixture: ComponentFixture<TestComponentWrapper>;

  beforeEach(async () => {
    await TestBed.configureTestingModule({
      declarations: [ 
        TestComponentWrapper,
        ProductThumbnail
      ],
      schemas: [CUSTOM_ELEMENTS_SCHEMA]
    })
    .compileComponents();

    fixture = TestBed.createComponent(TestComponentWrapper);
    component = fixture.debugElement.children[0].componentInstance;
    fixture.detectChanges();
  });

  it('should create', () => {
    expect(component).toBeTruthy();
  });
});

@Component({
  selector: 'test-component-wrapper',
  template: '<product-thumbnail [product]="product"></product-thumbnail>'
})
class TestComponentWrapper {
  product = new Product()
}

Answer 5

Answer №3

Make sure to assign the product value to the component instance after it's been loaded during testing.

For example, consider this basic component with an input that can serve as a starting point for your scenario:

@Component({
  selector: 'dropdown',
  directives: [NgClass],
  template: `
    <div [ngClass]="{open: open}">
    </div>
  `,
})
export class DropdownComponent {
  @Input('open') open: boolean = false;

  ngOnChanges() {
    console.log(this.open);
  }
}

Below is the corresponding test script:

it('should open', injectAsync([TestComponentBuilder], (tcb: TestComponentBuilder) => {
  return tcb.createAsync(DropdownComponent)
  .then(fixture => {
    let el = fixture.nativeElement;
    let comp: DropdownComponent = fixture.componentInstance;

    expect(el.className).toEqual('');

    // Update the input
    comp.open = true; // <-----------

    // Apply changes
    fixture.detectChanges(); // <-----------

    var div = fixture.nativeElement.querySelector('div');
    // Verify elements based on the input
    expect(div.className).toEqual('open');
  });
}));

Check out this plunkr link for reference: https://plnkr.co/edit/YAVD4s?p=preview.

Answer 6

Make sure to assign the product value to the component instance after it's been loaded during testing.

For example, consider this basic component with an input that can serve as a starting point for your scenario:

@Component({
  selector: 'dropdown',
  directives: [NgClass],
  template: `
    <div [ngClass]="{open: open}">
    </div>
  `,
})
export class DropdownComponent {
  @Input('open') open: boolean = false;

  ngOnChanges() {
    console.log(this.open);
  }
}

Below is the corresponding test script:

it('should open', injectAsync([TestComponentBuilder], (tcb: TestComponentBuilder) => {
  return tcb.createAsync(DropdownComponent)
  .then(fixture => {
    let el = fixture.nativeElement;
    let comp: DropdownComponent = fixture.componentInstance;

    expect(el.className).toEqual('');

    // Update the input
    comp.open = true; // <-----------

    // Apply changes
    fixture.detectChanges(); // <-----------

    var div = fixture.nativeElement.querySelector('div');
    // Verify elements based on the input
    expect(div.className).toEqual('open');
  });
}));

Check out this plunkr link for reference: https://plnkr.co/edit/YAVD4s?p=preview.

Answer 7

Answer №4

My usual approach for testing the ProductThumbnail component is as follows:

describe('ProductThumbnail', ()=> {
  it('should work',
    injectAsync([ TestComponentBuilder ], (tcb: TestComponentBuilder) => {
      return tcb.createAsync(TestCmpWrapper).then(rootCmp => {
        let cmpInstance: ProductThumbnail =  
               <ProductThumbnail>rootCmp.debugElement.children[ 0 ].componentInstance;

        expect(cmpInstance.openProductPage()).toBe(/* whatever */)
      });
  }));
}

@Component({
 selector  : 'test-cmp',
 template  : '<product-thumbnail [product]="mockProduct"></product-thumbnail>',
 directives: [ ProductThumbnail ]
})
class TestCmpWrapper { 
    mockProduct = new Product(); //mock your input 
}

It's important to note that in this method, fields like product in the ProductThumbnail class can be kept private, which is why I prefer this approach over others despite being slightly more verbose.

Answer 8

My usual approach for testing the ProductThumbnail component is as follows:

describe('ProductThumbnail', ()=> {
  it('should work',
    injectAsync([ TestComponentBuilder ], (tcb: TestComponentBuilder) => {
      return tcb.createAsync(TestCmpWrapper).then(rootCmp => {
        let cmpInstance: ProductThumbnail =  
               <ProductThumbnail>rootCmp.debugElement.children[ 0 ].componentInstance;

        expect(cmpInstance.openProductPage()).toBe(/* whatever */)
      });
  }));
}

@Component({
 selector  : 'test-cmp',
 template  : '<product-thumbnail [product]="mockProduct"></product-thumbnail>',
 directives: [ ProductThumbnail ]
})
class TestCmpWrapper { 
    mockProduct = new Product(); //mock your input 
}

It's important to note that in this method, fields like product in the ProductThumbnail class can be kept private, which is why I prefer this approach over others despite being slightly more verbose.

Testing Angular 2 components with Input properties provided

Answer №1

Answer №2

Answer №3

Answer №4

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