Testing the click functionality in Angular components

Question

Testing the click functionality in Angular components

I am currently in the process of implementing unit tests for my Angular 2 application. One of the components includes a button with a (click) handler that triggers a function defined in the .ts class file. This function logs a message in the console when the button is clicked. My existing test code verifies the logging of this message:

describe('Component: ComponentToBeTested', () => {
    var component: ComponentToBeTested;

    beforeEach(() => {
        component = new ComponentToBeTested();
        spyOn(console, 'log');
    });

    it('should call onEditButtonClick() and print console.log', () => {
        component.onEditButtonClick();
        expect(console.log).toHaveBeenCalledWith('Edit button has been clicked!);
    });
});

However, this current test only focuses on testing the controller class and does not cover the HTML aspect. I want to ensure not only that the log message is printed when onEditButtonClick is called, but also that the function is actually triggered when the edit button in the component's HTML file is clicked. How can I achieve this dual testing approach?

angular typescript jasmine

Answer 1

Answer №1

I am aiming to verify if the 'onEditButtonClick' function is triggered upon clicking the edit button, rather than solely relying on the console.log output.

To accomplish this, you should first set up a test using Angular's TestBed. By doing so, you can actively interact with the button and simulate a click event. Essentially, you will configure a module specifically for testing purposes, similar to setting up an @NgModule.

import { TestBed, async, ComponentFixture } from '@angular/core/testing';

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

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      imports: [ ],
      declarations: [ TestComponent ],
      providers: [  ]
    }).compileComponents().then(() => {
      fixture = TestBed.createComponent(TestComponent);
      component = fixture.componentInstance;
    });
  }));
});

Next, you need to spy on the onEditButtonClick method, simulate a button click, and verify that the method was indeed called.

it('should', async(() => {
  spyOn(component, 'onEditButtonClick');

  let button = fixture.debugElement.nativeElement.querySelector('button');
  button.click();

  fixture.whenStable().then(() => {
    expect(component.onEditButtonClick).toHaveBeenCalled();
  });
}));

It is crucial to run an async test since the button click involves asynchronous event handling. You must wait for the event processing by utilizing fixture.whenStable().

Update

Currently, it is recommended to use the fakeAsync/tick combination instead of async/whenStable, especially when XHR calls are not involved. If XHR calls are made, the latter should be utilized as fakeAsync does not support them. To refactor the above code accordingly:

it('should', fakeAsync(() => {
  spyOn(component, 'onEditButtonClick');

  let button = fixture.debugElement.nativeElement.querySelector('button');
  button.click();
  tick();
  expect(component.onEditButtonClick).toHaveBeenCalled();

}));

Ensure that you import both fakeAsync and tick in your test file.

Update

Currently, it is recommended to use the fakeAsync/tick combination instead of async/whenStable, especially when XHR calls are not involved. If XHR calls are made, the latter should be utilized as fakeAsync does not support them. To refactor the above code accordingly:

it('should', fakeAsync(() => {
  spyOn(component, 'onEditButtonClick');

  let button = fixture.debugElement.nativeElement.querySelector('button');
  button.click();
  tick();
  expect(component.onEditButtonClick).toHaveBeenCalled();

}));

Ensure that you import both fakeAsync and tick in your test file.

Answer №2

When testing events in Angular, the async/fakeAsync functions from '@angular/core/testing' can be used. This is because browser events are asynchronous and added to the event loop/queue.

Here's a simple example demonstrating how to test a click event using fakeAsync.

The fakeAsync function allows for a more linear coding style by executing the test body within a designated fakeAsync test zone.

In this case, a method triggered by a click event is being tested.

it('should', fakeAsync( () => {
    fixture.detectChanges();
    spyOn(componentInstance, 'method name'); //method attached to the click.
    let btn = fixture.debugElement.query(By.css('button'));
    btn.triggerEventHandler('click', null);
    tick(); // simulates the passage of time until all pending asynchronous activities finish
    fixture.detectChanges();
    expect(componentInstance.methodName).toHaveBeenCalled();
}));

The Angular docs highlight the following:

One key advantage of using fakeAsync instead of async is that the test feels synchronous. There's no then(...) disrupting the flow. The promise-based fixture.whenStable is replaced by tick()

However, there are some limitations such as not being able to make XHR calls within a fakeAsync block

Answer 4

When testing events in Angular, the async/fakeAsync functions from '@angular/core/testing' can be used. This is because browser events are asynchronous and added to the event loop/queue.

Here's a simple example demonstrating how to test a click event using fakeAsync.

The fakeAsync function allows for a more linear coding style by executing the test body within a designated fakeAsync test zone.

In this case, a method triggered by a click event is being tested.

it('should', fakeAsync( () => {
    fixture.detectChanges();
    spyOn(componentInstance, 'method name'); //method attached to the click.
    let btn = fixture.debugElement.query(By.css('button'));
    btn.triggerEventHandler('click', null);
    tick(); // simulates the passage of time until all pending asynchronous activities finish
    fixture.detectChanges();
    expect(componentInstance.methodName).toHaveBeenCalled();
}));

The Angular docs highlight the following:

One key advantage of using fakeAsync instead of async is that the test feels synchronous. There's no then(...) disrupting the flow. The promise-based fixture.whenStable is replaced by tick()

However, there are some limitations such as not being able to make XHR calls within a fakeAsync block

Answer 5

Answer №3

I have recently been using Angular 6 for my projects. Following a suggestion from Mav55, I decided to experiment with the code provided and found interesting results. Initially, I doubted the necessity of fixture.detectChanges(); but after removing it, the functionality still persisted. Curious, I then removed tick(); and surprisingly, everything continued to work flawlessly. Eventually, I even took the test out of the fakeAsync() wrap and to my amazement, it still functioned properly.

After these series of tests, I ended up simplifying the code to the following:

it('should call onClick method', () => {
  const onClickMock = spyOn(component, 'onClick');
  fixture.debugElement.query(By.css('button')).triggerEventHandler('click', null);
  expect(onClickMock).toHaveBeenCalled();
});

To my satisfaction, this revised version worked perfectly fine as well.

Answer 6

I have recently been using Angular 6 for my projects. Following a suggestion from Mav55, I decided to experiment with the code provided and found interesting results. Initially, I doubted the necessity of fixture.detectChanges(); but after removing it, the functionality still persisted. Curious, I then removed tick(); and surprisingly, everything continued to work flawlessly. Eventually, I even took the test out of the fakeAsync() wrap and to my amazement, it still functioned properly.

After these series of tests, I ended up simplifying the code to the following:

it('should call onClick method', () => {
  const onClickMock = spyOn(component, 'onClick');
  fixture.debugElement.query(By.css('button')).triggerEventHandler('click', null);
  expect(onClickMock).toHaveBeenCalled();
});

To my satisfaction, this revised version worked perfectly fine as well.

Answer 7

Answer №4

Before checking the button event, it is important to spy on the method that will be triggered upon clicking the button. To do this, we use the spyOn function. The spyOn function requires two arguments: 1) The component name 2) The method to be spied on, for example, 'onSubmit'. Only the name should be used without parentheses. Next, create an object representing the button that will be clicked. Then, trigger the event handler where we will add a click event. Finally, our code expects the submit method to be called once.

it('should call onSubmit method',() => {
    spyOn(component, 'onSubmit');
    let submitButton: DebugElement = 
    fixture.debugElement.query(By.css('button[type=submit]'));
    fixture.detectChanges();
    submitButton.triggerEventHandler('click',null);
    fixture.detectChanges();
    expect(component.onSubmit).toHaveBeenCalledTimes(1);
});

Answer 8

Before checking the button event, it is important to spy on the method that will be triggered upon clicking the button. To do this, we use the spyOn function. The spyOn function requires two arguments: 1) The component name 2) The method to be spied on, for example, 'onSubmit'. Only the name should be used without parentheses. Next, create an object representing the button that will be clicked. Then, trigger the event handler where we will add a click event. Finally, our code expects the submit method to be called once.

it('should call onSubmit method',() => {
    spyOn(component, 'onSubmit');
    let submitButton: DebugElement = 
    fixture.debugElement.query(By.css('button[type=submit]'));
    fixture.detectChanges();
    submitButton.triggerEventHandler('click',null);
    fixture.detectChanges();
    expect(component.onSubmit).toHaveBeenCalledTimes(1);
});

Answer 9

Answer №5

I encountered a similar issue, which I managed to resolve by utilizing the tick function in jasmine-core: 2.52. It was crucial to ensure that the time delay specified in tick matched or exceeded the milliseconds set in the original setTimeout call.

For instance, if a setTimeout(() => {...}, 2500); was implemented (to trigger after 2500 ms), calling tick(2500) effectively resolved the issue.

In one of my components, in response to a click on the Delete button:

delete() {
    this.myService.delete(this.id)
      .subscribe(
        response => {
          this.message = 'Successfully deleted! Redirecting...';
          setTimeout(() => {
            this.router.navigate(['/home']);
          }, 2500); // Wait for 2.5 seconds before redirecting
        });
}

Below is an example of a functional test scenario:

it('should delete the entity', fakeAsync(() => {
    component.id = 1; 
    component.getEntity(); 
    tick(); 
    expect(myService.getMyThing).toHaveBeenCalledWith(1);
    
    fixture.detectChanges();
    tick();
    fixture.detectChanges();
    
    const deleteButton = fixture.debugElement.query(By.css('.btn-danger')).nativeElement;
    deleteButton.click(); 

    tick(2501); // Delay for redirect set at 2500 ms

    expect(myService.delete).toHaveBeenCalledWith(1);
    // More expectations...
}));

P.S. For detailed information on fakeAsync and handling async tasks in testing, watch this informative video: a video on Testing strategies with Angular 2 - Julie Ralph, starting from 8:10, lasting 4 minutes :)

Answer 10

I encountered a similar issue, which I managed to resolve by utilizing the tick function in jasmine-core: 2.52. It was crucial to ensure that the time delay specified in tick matched or exceeded the milliseconds set in the original setTimeout call.

For instance, if a setTimeout(() => {...}, 2500); was implemented (to trigger after 2500 ms), calling tick(2500) effectively resolved the issue.

In one of my components, in response to a click on the Delete button:

delete() {
    this.myService.delete(this.id)
      .subscribe(
        response => {
          this.message = 'Successfully deleted! Redirecting...';
          setTimeout(() => {
            this.router.navigate(['/home']);
          }, 2500); // Wait for 2.5 seconds before redirecting
        });
}

Below is an example of a functional test scenario:

it('should delete the entity', fakeAsync(() => {
    component.id = 1; 
    component.getEntity(); 
    tick(); 
    expect(myService.getMyThing).toHaveBeenCalledWith(1);
    
    fixture.detectChanges();
    tick();
    fixture.detectChanges();
    
    const deleteButton = fixture.debugElement.query(By.css('.btn-danger')).nativeElement;
    deleteButton.click(); 

    tick(2501); // Delay for redirect set at 2500 ms

    expect(myService.delete).toHaveBeenCalledWith(1);
    // More expectations...
}));

P.S. For detailed information on fakeAsync and handling async tasks in testing, watch this informative video: a video on Testing strategies with Angular 2 - Julie Ralph, starting from 8:10, lasting 4 minutes :)

Answer 11

Answer №6

In scenarios where you don't have a specific CSS class to target, you can rely on using a function match based on attributes that are relevant to your case.

it('should trigger onClick when button element is clicked', fakeAsync(() => {
  spyOn(component, 'onClick').and.callFake(() => null);

  fixture.detectChanges();

  const button = fixture.debugElement.query(
    (val) => val.attributes['id'] === 'button-1'
  );

  expect(button).toBeTruthy();

  trashCanButton.children[0].triggerEventHandler('click', {});

  tick(1000);

  expect(component.onClick).toHaveBeenCalledTimes(1);
}));

Answer 12

In scenarios where you don't have a specific CSS class to target, you can rely on using a function match based on attributes that are relevant to your case.

it('should trigger onClick when button element is clicked', fakeAsync(() => {
  spyOn(component, 'onClick').and.callFake(() => null);

  fixture.detectChanges();

  const button = fixture.debugElement.query(
    (val) => val.attributes['id'] === 'button-1'
  );

  expect(button).toBeTruthy();

  trashCanButton.children[0].triggerEventHandler('click', {});

  tick(1000);

  expect(component.onClick).toHaveBeenCalledTimes(1);
}));

Testing the click functionality in Angular components

Answer №1

Update

See also:

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

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