Error encountered during Angular unit testing: Unable to read the 'id' property of a null value. (Jasmine, Karma)

Question

Error encountered during Angular unit testing: Unable to read the 'id' property of a null value. (Jasmine, Karma)

I am currently working on writing unit tests for a specific component in my Angular application. The component uses a currentUser variable both in the component logic and the HTML template. I have hardcoded this variable by mocking it in every test using component.currentUser = {...}. However, I am encountering failures when running Karma tests. Any help or suggestions would be greatly appreciated.

UserProfileComponent > should create
TypeError: Cannot read property 'id' of null
    at UserProfileComponent.ngOnInit (http://localhost:9877/_karma_webpack_/webpack:/src/app/modules/user-profile/page/user-profile/user-profile.component.ts:4:21)
    at callHook (http://localhost:9877/_karma_webpack_/webpack:/node_modules/@angular/core/__ivy_ngcc__/fesm2015/core.js:2573:1)
    at callHooks (http://localhost:9877/_karma_webpack_/webpack:/node_modules/@angular/core/__ivy_ngcc__/fesm2015/core.js:2542:1)
    at executeInitAndCheckHooks (http://localhost:9877/_karma_webpack_/webpack:/node_modules/@angular/core/__ivy_ngcc__/fesm2015/core.js:2493:1)
    at refreshView (http://localhost:9877/_karma_webpack_/webpack:/node_modules/@angular/core/__ivy_ngcc__/fesm2015/core.js:9481:1)
    at renderComponentOrTemplate (http://localhost:9877/_karma_webpack_/webpack:/node_modules/@angular/core/__ivy_ngcc__/fesm2015/core.js:9580:1)
    at tickRootContext (http://localhost:9877/_karma_webpack_/webpack:/node_modules/@angular/core/__ivy_ngcc__/fesm2015/core.js:10811:1)
    at detectChangesInRootView (http://localhost:9877/_karma_webpack_/webpack:/node_modules/@angular/core/__ivy_ngcc__/fesm2015/core.js:10836:1)
    at RootViewRef.detectChanges (http://localhost:9877/_karma_webpack_/webpack:/node_modules/@angular/core/__ivy_ngcc__/fesm2015/core.js:22815:1)
    at ComponentFixture._tick (http://localhost:9877/_karma_webpack_/webpack:/node_modules/@angular/core/__ivy_ngcc__/fesm2015/testing.js:141:1)

Below is an example of the code.

user-profile.component.ts

ngOnInit(): void {
    this.currentUser = this.userService.getUser();
    console.log(this.currentUser.id);
    this.userAnnouncements();
  }

user-profile.component.spec.ts

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

  beforeEach(async () => {
    await TestBed.configureTestingModule({
      imports: [HttpClientTestingModule, RouterTestingModule],
      declarations: [UserProfileComponent],
      schemas: [CUSTOM_ELEMENTS_SCHEMA],
    }).compileComponents();
  });

  beforeEach(() => {
    fixture = TestBed.createComponent(UserProfileComponent);
    component = fixture.componentInstance;
    component.currentUser = {
      id: 1,
      email: '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="7716131a1e193716131a1e195914181a">[email protected]</a>',
      firstname: 'admin',
      img_name: 'photo',
      lastname: 'admin',
      location: 1,
      password: 'hashed_pass',
      role: 'admin',
      username: 'admin',
    };
    fixture.detectChanges();
  });

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

javascript angular typescript unit-testing karma-jasmine

Answer 1

Answer №1

The main issue here is the absence of data mocking for userService, which leads to the override of the value being set.

To address this, it is crucial to properly mock the service as demonstrated below:

describe('UserProfileComponent', () => {
  let component: UserProfileComponent;
  let fixture: ComponentFixture<UserProfileComponent>;
  let userService: jasmine.SpyObj<UserService>;
  beforeEach(async () => {
    const userServiceSpy = jasmine.createSpyObj('UserService', ['getUser']);
    await TestBed.configureTestingModule({
      imports: [HttpClientTestingModule, RouterTestingModule],
      declarations: [UserProfileComponent],
      providers: [ {provide: UserService, useValue: userServiceSpy }],
      schemas: [CUSTOM_ELEMENTS_SCHEMA],
    }).compileComponents();
  });

  beforeEach(() => {
    userService = TestBed.inject(UserService) as jasmine.SpyObj<UserService>;
    userService.getUser.and.returnValue({
      id: 1,
      email: '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="6607020b0f082607020b0f084805090b">[email protected]</a>',
      firstname: 'admin',
      img_name: 'photo',
      lastname: 'admin',
      location: 1,
      password: 'hashed_pass',
      role: 'admin',
      username: 'admin',
    });
    fixture = TestBed.createComponent(UserProfileComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

  it('should create', () => {
    expect(component).toBeTruthy();
    expect(component.currentUser.id).toBe(1)
  });
});

For further insights on unit testing with best practices, I suggest checking out this informative article collection.

Answer 2

The main issue here is the absence of data mocking for userService, which leads to the override of the value being set.

To address this, it is crucial to properly mock the service as demonstrated below:

describe('UserProfileComponent', () => {
  let component: UserProfileComponent;
  let fixture: ComponentFixture<UserProfileComponent>;
  let userService: jasmine.SpyObj<UserService>;
  beforeEach(async () => {
    const userServiceSpy = jasmine.createSpyObj('UserService', ['getUser']);
    await TestBed.configureTestingModule({
      imports: [HttpClientTestingModule, RouterTestingModule],
      declarations: [UserProfileComponent],
      providers: [ {provide: UserService, useValue: userServiceSpy }],
      schemas: [CUSTOM_ELEMENTS_SCHEMA],
    }).compileComponents();
  });

  beforeEach(() => {
    userService = TestBed.inject(UserService) as jasmine.SpyObj<UserService>;
    userService.getUser.and.returnValue({
      id: 1,
      email: '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="6607020b0f082607020b0f084805090b">[email protected]</a>',
      firstname: 'admin',
      img_name: 'photo',
      lastname: 'admin',
      location: 1,
      password: 'hashed_pass',
      role: 'admin',
      username: 'admin',
    });
    fixture = TestBed.createComponent(UserProfileComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

  it('should create', () => {
    expect(component).toBeTruthy();
    expect(component.currentUser.id).toBe(1)
  });
});

For further insights on unit testing with best practices, I suggest checking out this informative article collection.

Answer 3

Answer №2

If you're facing an issue, don't worry! There is a simple solution to resolve it by following these steps:

// Modify your service file as shown below:

@Injectable() 
class MockUserService extends UserService {
  getUser() {
    const mockData = {
      id: 1,
      email: '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="78191c15111638191c151116561b1715">[email protected]</a>',
      firstname: 'admin',
      img_name: 'photo',
      lastname: 'admin',
      location: 1,
      password: 'hashed_pass',
      role: 'admin',
      username: 'admin',
    };
    
    return mockData;
  }

  // Feel free to include additional methods that your service offers and mock them here
}


describe('UserProfileComponent', () => {
  let component: UserProfileComponent;
  let fixture: ComponentFixture<UserProfileComponent>;
  beforeEach(async () => {
    await TestBed.configureTestingModule({
      imports: [HttpClientTestingModule, RouterTestingModule],
      declarations: [UserProfileComponent],
      providers: [{
         provide: UserService, 
         useClass: MockUserService 
      }],
      schemas: [CUSTOM_ELEMENTS_SCHEMA],
    }).compileComponents();
  });

  beforeEach(() => {
    fixture = TestBed.createComponent(UserProfileComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

  it('should create', () => {
    expect(component).toBeTruthy();
    expect(component.currentUser.id).toBe(1)
  });

  it('should run #ngOnInit() method', () => {
     spyOn(component, 'ngOnInit').and.callThrough();
     component.ngOnInit();
     expect(component.ngOnInit).toHaveBeenCalled(); 
  });
});

Answer 4

If you're facing an issue, don't worry! There is a simple solution to resolve it by following these steps:

// Modify your service file as shown below:

@Injectable() 
class MockUserService extends UserService {
  getUser() {
    const mockData = {
      id: 1,
      email: '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="78191c15111638191c151116561b1715">[email protected]</a>',
      firstname: 'admin',
      img_name: 'photo',
      lastname: 'admin',
      location: 1,
      password: 'hashed_pass',
      role: 'admin',
      username: 'admin',
    };
    
    return mockData;
  }

  // Feel free to include additional methods that your service offers and mock them here
}


describe('UserProfileComponent', () => {
  let component: UserProfileComponent;
  let fixture: ComponentFixture<UserProfileComponent>;
  beforeEach(async () => {
    await TestBed.configureTestingModule({
      imports: [HttpClientTestingModule, RouterTestingModule],
      declarations: [UserProfileComponent],
      providers: [{
         provide: UserService, 
         useClass: MockUserService 
      }],
      schemas: [CUSTOM_ELEMENTS_SCHEMA],
    }).compileComponents();
  });

  beforeEach(() => {
    fixture = TestBed.createComponent(UserProfileComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

  it('should create', () => {
    expect(component).toBeTruthy();
    expect(component.currentUser.id).toBe(1)
  });

  it('should run #ngOnInit() method', () => {
     spyOn(component, 'ngOnInit').and.callThrough();
     component.ngOnInit();
     expect(component.ngOnInit).toHaveBeenCalled(); 
  });
});

Error encountered during Angular unit testing: Unable to read the 'id' property of a null value. (Jasmine, Karma)

Answer №1

Answer №2

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