I'm struggling to comprehend the behavior of the automatically generated .spec.ts tests in Angular. Each test contains expect(component).toBeTruthy();, which should be a straightforward check to verify if the component was created successfully. However, I'm puzzled by the fact that about half of these tests pass while the other half fail without any clear pattern.
For instance, let's consider a header element that is clearly visible on every page of the application:
Error: Expected undefined to be truthy.
at <Jasmine>
at UserContext.<anonymous> (http://localhost:9876/_karma_webpack_/src/app/header-page/header-page.component.spec.ts:24:23)
at ZoneDelegate.invoke (http://localhost:9876/_karma_webpack_/node_modules/zone.js/dist/zone-evergreen.js:364:1)
at ProxyZoneSpec.push../node_modules/zone.js/dist/zone-testing.js.ProxyZoneSpec.onInvoke (http://localhost:9876/_karma_webpack_/node_modules/zone.js/dist/zone-testing.js:292:1)
In contrast, other components have seemingly identical tests for 'should create' or 'should create an instance', and they pass smoothly.
I've been referring to the Angular documentation but haven't found a starting point to address this issue. Why do the auto-generated tests fail intermittently? Should I analyze each test individually? Could the visibility of the component on the client's screen impact the test results? Should I explore settings in the karma.conf.js file? The project runs error-free, so what sections of the code should I share to facilitate a solution?
import { Component, OnInit } from '@angular/core';
import { LoginPageComponent } from '../login-page/login-page.component';
@Component({
selector: 'app-header-page',
templateUrl: './header-page.component.html',
styleUrls: ['./header-page.component.css']
})
export class HeaderPageComponent implements OnInit {
constructor(public loginService: LoginPageComponent) { }
ngOnInit(): void {
}
}
<header>
<nav class ="navbar navbar-expand-md navbar-dark bg-dark">
<div><a href="http://localhost:4200/" class="navbar-brand">Computer Store</a></div>
<ul class="navbar-nav">
<li class="nav-item"><a *ngIf="!loginService.isUserLoggedIn()" routerLink="/user" class="nav-link">Create User</a></li>
<li class="nav-item"><a *ngIf="loginService.isUserLoggedIn()" routerLink="/shopmain" class="nav-link">Shop Computer Parts</a></li>
</ul>
<ul class="navbar-nav ml-auto">
<li class="nav-item"><a *ngIf="!loginService.isUserLoggedIn()" routerLink="/loginpage" class="nav-link">Log In</a></li>
<li class="nav-item"><a *ngIf="loginService.isUserLoggedIn()" routerLink="/logout" class="nav-link">LogOut</a></li>
</ul>
</nav>
</header>
HeaderPageComponent > should create
NullInjectorError: R3InjectorError(DynamicTestModule)[LoginPageComponent -> LoginPageComponent]:
NullInjectorError: No provider for LoginPageComponent!
error properties: Object({ ngTempTokenPath: null, ngTokenPath: [ 'LoginPageComponent', 'LoginPageComponent' ] })
at <Jasmine>
...
Expected undefined to be truthy.
Error: Expected undefined to be truthy.
at <Jasmine>
...
import { async, ComponentFixture, TestBed } from '@angular/core/testing';
import { HeaderPageComponent } from './header-page.component';
fdescribe('HeaderPageComponent', () => {
let component: HeaderPageComponent;
let fixture: ComponentFixture<HeaderPageComponent>;
beforeEach(async(() => {
TestBed.configureTestingModule({
declarations: [ HeaderPageComponent ]
})
.compileComponents();
}));
beforeEach(() => {
fixture = TestBed.createComponent(HeaderPageComponent);
component = fixture.componentInstance;
fixture.detectChanges();
});
it('should create', () => {
expect(component).toBeTruthy();
});
});