Html code block not displayed inside defer block in Angular v17

[MattiaMalandrone]

Current behavior

Trying testing new angular control flow the html inside a defer block is not displayed when running test in component testing inside cypress

describe('AppComponent.cy.ts', () => {
  it('should mount', () => {
    cy.mount(AppComponent)
  })
})

app.component.html

outside defer

@defer() {
  inside defer
}

@defer(on timer(500ms)) {
  inside defer with condition
}

Only string "outside defer" is displayed

Desired behavior

I expect that html code inside a defer block will be displayed

Test code to reproduce

https://github.com/MattiaMalandrone/cypress-defer-block-angular17

launching npx cypress open -> component testing -> chrome -> AppComponent.cy.ts

Cypress Version

13.5.0

Node version

18.18.2

Operating System

windows 10

Debug Logs

No response

Other

No response

[kanidjar]

Same issue here. Critical bug on my side since i cannot test my components.

[MattiaMalandrone]

any news about it?

[felixgeissler]

We are experiencing the same behaviour in our component tests running v13.5.1

[psrebrny]

I confirm this behaviour in cypress v13.6.1 when can we expect to handle defer in component testing?

[psrebrny]

I have written a workaround for this issue

Service:

import { Injectable, signal, Signal } from '@angular/core';

@Injectable({
    providedIn: 'root',
})
export class DeferrableStateService {
    defer: Signal<boolean> = signal(true);
    constructor() {}
}

Component:

import { ChangeDetectionStrategy, Component, Input } from '@angular/core';
import { DeferrableStateService } from '../../services/deferrable-state.service';
import { NgTemplateOutlet } from '@angular/common';

@Component({
    selector: 'app-deferrer',
    standalone: true,
    imports: [NgTemplateOutlet],
    templateUrl: './deferrer.component.html',
    changeDetection: ChangeDetectionStrategy.OnPush,
})
export class DeferrerComponent {
    isdeferred = this.deferrableStateService.defer;
    constructor(private deferrableStateService: DeferrableStateService) {}
}

and HTML for that component:

<ng-template #content>
    <ng-content></ng-content>
</ng-template>

@if (isdeferred()) { @defer (on viewport) {
<ng-container *ngTemplateOutlet="content"></ng-container>
} @placeholder () {
 // your placeholder
} } @else {
<ng-container *ngTemplateOutlet="content"></ng-container>
}

then in component test add configuration

cy.mount(Component, {
  imports: [
      // YourComponents and/or modules
  ],
  providers: [
      {
          provide: DeferrableStateService,
          useValue: {
              defer: signal(false),
          },
      },
  ],
  declarations: [],
  componentProperties: {
      // your properties
  },
 
});

[jordanpowell88]

Hey @MattiaMalandrone thanks for opening this issue. I went ahead and created an example repo and blog article to highlight how you can do this. https://dev.to/angular/testing-defer-blocks-in-angular-with-cypress-21j8

Hopefully this helps!

[jordanpowell88]

I'm going to close this for now but we may create something more "official" in the future

[MattiaMalandrone]

Hey @MattiaMalandrone thanks for opening this issue. I went ahead and created an example repo and blog article to highlight how you can do this. https://dev.to/angular/testing-defer-blocks-in-angular-with-cypress-21j8

Hopefully this helps!

Thanks Jordan!!!!