Testing the value of an input in Angular using unit tests

Question

Testing the value of an input in Angular using unit tests

Currently, I am delving into the official documentation of Angular2 which focuses on unit testing (https://angular.io/docs/ts/latest/guide/testing.html). My struggle lies in setting a component's input field value so that it reflects in the component property bound via ngModel. The application works seamlessly in the browser, however, when it comes to running unit tests, I face difficulty in changing the field's value.

The code snippet I am using is shown below. "fixture" initialization is correct as other tests are functioning properly. "comp" represents the instance of my component and the input field is linked to "user.username" through ngModel.

it('should update model...', async(() => {
    let field: HTMLInputElement = fixture.debugElement.query(By.css('#user')).nativeElement;
    field.value = 'someValue'
    field.dispatchEvent(new Event('input'));
    fixture.detectChanges();

    expect(field.textContent).toBe('someValue');
    expect(comp.user.username).toBe('someValue');
}));

My Angular2 version: "@angular/core": "2.0.0"

angular unit-testing angular2-testing

Answer 1

Answer №1

TextContent cannot be retrieved from inputs, only their value. Therefore, using

expect(field.textContent).toBe('someValue');

is not valid. This is likely the reason for the failure. However, the second expectation should succeed. Below is a complete test example:

@Component({
  template: `<input type="text" [(ngModel)]="user.username"/>`
})
class TestComponent {
  user = { username: 'peeskillet' };
}

describe('component: TestComponent', () => {
  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [FormsModule],
      declarations: [ TestComponent ]
    });
  });

  it('should be ok', async(() => {
    let fixture = TestBed.createComponent(TestComponent);
    fixture.detectChanges();
    fixture.whenStable().then(() => {
      let input = fixture.debugElement.query(By.css('input'));
      let el = input.nativeElement;

      expect(el.value).toBe('peeskillet');

      el.value = 'someValue';
      el.dispatchEvent(new Event('input'));

      expect(fixture.componentInstance.user.username).toBe('someValue');
    });
  }));
});

The key aspect is the initial fixture.whenStable(). Since there is asynchronous form setup happening, we must wait for it to complete after calling fixture.detectChanges(). If you are using fakeAsync() instead of async(), then simply use tick() after fixture.detectChanges().

Answer 2

TextContent cannot be retrieved from inputs, only their value. Therefore, using

expect(field.textContent).toBe('someValue');

is not valid. This is likely the reason for the failure. However, the second expectation should succeed. Below is a complete test example:

@Component({
  template: `<input type="text" [(ngModel)]="user.username"/>`
})
class TestComponent {
  user = { username: 'peeskillet' };
}

describe('component: TestComponent', () => {
  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [FormsModule],
      declarations: [ TestComponent ]
    });
  });

  it('should be ok', async(() => {
    let fixture = TestBed.createComponent(TestComponent);
    fixture.detectChanges();
    fixture.whenStable().then(() => {
      let input = fixture.debugElement.query(By.css('input'));
      let el = input.nativeElement;

      expect(el.value).toBe('peeskillet');

      el.value = 'someValue';
      el.dispatchEvent(new Event('input'));

      expect(fixture.componentInstance.user.username).toBe('someValue');
    });
  }));
});

The key aspect is the initial fixture.whenStable(). Since there is asynchronous form setup happening, we must wait for it to complete after calling fixture.detectChanges(). If you are using fakeAsync() instead of async(), then simply use tick() after fixture.detectChanges().

Answer 3

Answer №2

Simply include

fixture.detectChanges();

fixture.whenStable().then(() => {
  // define your expectation here
})

Answer 4

Simply include

fixture.detectChanges();

fixture.whenStable().then(() => {
  // define your expectation here
})

Answer 5

Answer №3

To incorporate your expect/assert statements into the whenStable.then function, follow this example:

component.text = 'hello';
fixture.detectChanges();

fixture.whenStable().then(() => {
    expect(component.text).toBe('hello');
}

Answer 6

To incorporate your expect/assert statements into the whenStable.then function, follow this example:

component.text = 'hello';
fixture.detectChanges();

fixture.whenStable().then(() => {
    expect(component.text).toBe('hello');
}

Answer 7

Answer №4

If you're looking to incorporate Unit Testing with @Input content, take a look at the following code snippet.

testing.component.ts

    import { Component, OnInit } from '@angular/core';
    @Component({
      selector: 'app-testing',
      templateUrl: `<app-input [message]='text'></app-input>`,
      styleUrls: ['./testing.component.css']
    })
    export class TestingComponent implements OnInit {
    public text = 'input message';
      constructor() { }
    
      ngOnInit() {
      }
    
    }

input.component.ts

    import { Component, OnInit, Input } from '@angular/core';
    
    @Component({
      selector: 'app-input',
      templateUrl: `<div *ngIf="message">{{message}}</div>`,
      styleUrls: ['./input.component.css']
    })
    export class InputComponent implements OnInit {
    @Input() public message: string;
      constructor() { }
    
      ngOnInit() {
        console.log(this.message);
      }
    
    }

input.component.spec.ts

    import { async, ComponentFixture, TestBed } from '@angular/core/testing';
    
    import { InputComponent } from './input.component';
    import { TestingComponent } from '../testing/testing.component';
    
    describe('InputComponent', () => {
      let component: InputComponent;
      let fixture: ComponentFixture<InputComponent>;
    
      beforeEach(async(() => {
        TestBed.configureTestingModule({
          declarations: [ InputComponent, TestingComponent ]
        })
        .compileComponents();
      }));
    
      beforeEach(() => {
        fixture = TestBed.createComponent(InputComponent);
        component = fixture.componentInstance;
        fixture.detectChanges();
      });
    
      it('should create', () => {
        expect(component).toBeTruthy();
      });
    
      it('should correctly render the passed @Input value', () => {
        component.message = 'test input';
        fixture.detectChanges();
        expect(fixture.nativeElement.innerText).toBe('test input');
      });
    
    });

Answer 8

If you're looking to incorporate Unit Testing with @Input content, take a look at the following code snippet.

testing.component.ts

    import { Component, OnInit } from '@angular/core';
    @Component({
      selector: 'app-testing',
      templateUrl: `<app-input [message]='text'></app-input>`,
      styleUrls: ['./testing.component.css']
    })
    export class TestingComponent implements OnInit {
    public text = 'input message';
      constructor() { }
    
      ngOnInit() {
      }
    
    }

input.component.ts

    import { Component, OnInit, Input } from '@angular/core';
    
    @Component({
      selector: 'app-input',
      templateUrl: `<div *ngIf="message">{{message}}</div>`,
      styleUrls: ['./input.component.css']
    })
    export class InputComponent implements OnInit {
    @Input() public message: string;
      constructor() { }
    
      ngOnInit() {
        console.log(this.message);
      }
    
    }

input.component.spec.ts

    import { async, ComponentFixture, TestBed } from '@angular/core/testing';
    
    import { InputComponent } from './input.component';
    import { TestingComponent } from '../testing/testing.component';
    
    describe('InputComponent', () => {
      let component: InputComponent;
      let fixture: ComponentFixture<InputComponent>;
    
      beforeEach(async(() => {
        TestBed.configureTestingModule({
          declarations: [ InputComponent, TestingComponent ]
        })
        .compileComponents();
      }));
    
      beforeEach(() => {
        fixture = TestBed.createComponent(InputComponent);
        component = fixture.componentInstance;
        fixture.detectChanges();
      });
    
      it('should create', () => {
        expect(component).toBeTruthy();
      });
    
      it('should correctly render the passed @Input value', () => {
        component.message = 'test input';
        fixture.detectChanges();
        expect(fixture.nativeElement.innerText).toBe('test input');
      });
    
    });

Testing the value of an input in Angular using unit tests

Answer №1

Answer №2

Answer №3

Answer №4

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