---
name: angular-testing
description: Write unit and integration tests for Angular v21+ applications using Vitest or Jasmine with TestBed, component harnesses, and modern testing patterns. Use for testing components with signals, OnPush change detection, services with inject(), and HTTP interactions. Triggers on test creation, testing signal-based components, mocking dependencies, or setting up test infrastructure.
---

# Angular Testing

Test Angular v21+ applications with Vitest (recommended) or Jasmine, focusing on signal-based components and modern patterns.

## Vitest Setup (Angular v20+)

Angular v20+ has native Vitest support through the `@angular/build` package.

### Installation

```bash
npm install -D vitest jsdom
```

### Configuration

```json
// angular.json - update test architect
{
  "projects": {
    "your-app": {
      "architect": {
        "test": {
          "builder": "@angular/build:unit-test",
          "options": {
            "tsConfig": "tsconfig.spec.json",
            "buildTarget": "your-app:build"
          }
        }
      }
    }
  }
}
```

```json
// tsconfig.spec.json
{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "types": ["vitest/globals"]
  },
  "include": ["src/**/*.spec.ts"]
}
```

### Running Tests

```bash
# Run tests
ng test

# Watch mode
ng test --watch

# Coverage
ng test --code-coverage
```

### Vitest Test Example

```typescript
import { describe, it, expect, beforeEach } from 'vitest';
import { ComponentFixture, TestBed } from '@angular/core/testing';
import { CounterComponent } from './counter.component';

describe('CounterComponent', () => {
  let component: CounterComponent;
  let fixture: ComponentFixture<CounterComponent>;
  
  beforeEach(async () => {
    await TestBed.configureTestingModule({
      imports: [CounterComponent],
    }).compileComponents();
    
    fixture = TestBed.createComponent(CounterComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });
  
  it('should create', () => {
    expect(component).toBeTruthy();
  });
  
  it('should increment count', () => {
    expect(component.count()).toBe(0);
    
    component.increment();
    
    expect(component.count()).toBe(1);
  });
});
```

### Vitest Mocking

```typescript
import { describe, it, expect, vi, beforeEach } from 'vitest';

describe('UserComponent', () => {
  const mockUserService = {
    getUser: vi.fn(),
    updateUser: vi.fn(),
    user: signal<User | null>(null),
  };
  
  beforeEach(async () => {
    vi.clearAllMocks();
    mockUserService.getUser.mockReturnValue(of({ id: '1', name: 'Test' }));
    
    await TestBed.configureTestingModule({
      imports: [UserComponent],
      providers: [
        { provide: UserService, useValue: mockUserService },
      ],
    }).compileComponents();
  });
  
  it('should call getUser on init', () => {
    const fixture = TestBed.createComponent(UserComponent);
    fixture.detectChanges();
    
    expect(mockUserService.getUser).toHaveBeenCalledWith('1');
  });
});
```

### Vitest with HTTP Testing

```typescript
import { describe, it, expect, beforeEach, afterEach } from 'vitest';
import { HttpTestingController, provideHttpClientTesting } from '@angular/common/http/testing';
import { provideHttpClient } from '@angular/common/http';

describe('UserService', () => {
  let service: UserService;
  let httpMock: HttpTestingController;
  
  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [
        provideHttpClient(),
        provideHttpClientTesting(),
      ],
    });
    
    service = TestBed.inject(UserService);
    httpMock = TestBed.inject(HttpTestingController);
  });
  
  afterEach(() => {
    httpMock.verify();
  });
  
  it('should fetch user', () => {
    const mockUser = { id: '1', name: 'Test User' };
    
    service.getUser('1').subscribe(user => {
      expect(user).toEqual(mockUser);
    });
    
    const req = httpMock.expectOne('/api/users/1');
    expect(req.request.method).toBe('GET');
    req.flush(mockUser);
  });
});
```

---

## Basic Component Test

```typescript
import { ComponentFixture, TestBed } from '@angular/core/testing';
import { CounterComponent } from './counter.component';

describe('CounterComponent', () => {
  let component: CounterComponent;
  let fixture: ComponentFixture<CounterComponent>;
  
  beforeEach(async () => {
    await TestBed.configureTestingModule({
      imports: [CounterComponent], // Standalone component
    }).compileComponents();
    
    fixture = TestBed.createComponent(CounterComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });
  
  it('should create', () => {
    expect(component).toBeTruthy();
  });
  
  it('should increment count', () => {
    expect(component.count()).toBe(0);
    
    component.increment();
    
    expect(component.count()).toBe(1);
  });
  
  it('should display count in template', () => {
    component.count.set(5);
    fixture.detectChanges();
    
    const element = fixture.nativeElement.querySelector('.count');
    expect(element.textContent).toContain('5');
  });
});
```

## Testing Signals

### Direct Signal Testing

```typescript
import { signal, computed } from '@angular/core';

describe('Signal logic', () => {
  it('should update computed when signal changes', () => {
    const count = signal(0);
    const doubled = computed(() => count() * 2);
    
    expect(doubled()).toBe(0);
    
    count.set(5);
    expect(doubled()).toBe(10);
    
    count.update(c => c + 1);
    expect(doubled()).toBe(12);
  });
});
```

### Testing Component Signals

```typescript
@Component({
  selector: 'app-todo-list',
  template: `
    <ul>
      @for (todo of filteredTodos(); track todo.id) {
        <li>{{ todo.text }}</li>
      }
    </ul>
    <p>{{ remaining() }} remaining</p>
  `,
})
export class TodoListComponent {
  todos = signal<Todo[]>([]);
  filter = signal<'all' | 'active' | 'done'>('all');
  
  filteredTodos = computed(() => {
    const todos = this.todos();
    switch (this.filter()) {
      case 'active': return todos.filter(t => !t.done);
      case 'done': return todos.filter(t => t.done);
      default: return todos;
    }
  });
  
  remaining = computed(() => this.todos().filter(t => !t.done).length);
}

describe('TodoListComponent', () => {
  let component: TodoListComponent;
  let fixture: ComponentFixture<TodoListComponent>;
  
  beforeEach(async () => {
    await TestBed.configureTestingModule({
      imports: [TodoListComponent],
    }).compileComponents();
    
    fixture = TestBed.createComponent(TodoListComponent);
    component = fixture.componentInstance;
  });
  
  it('should filter active todos', () => {
    component.todos.set([
      { id: '1', text: 'Task 1', done: false },
      { id: '2', text: 'Task 2', done: true },
      { id: '3', text: 'Task 3', done: false },
    ]);
    
    component.filter.set('active');
    
    expect(component.filteredTodos().length).toBe(2);
    expect(component.remaining()).toBe(2);
  });
  
  it('should render filtered todos', () => {
    component.todos.set([
      { id: '1', text: 'Active Task', done: false },
      { id: '2', text: 'Done Task', done: true },
    ]);
    component.filter.set('active');
    fixture.detectChanges();
    
    const items = fixture.nativeElement.querySelectorAll('li');
    expect(items.length).toBe(1);
    expect(items[0].textContent).toContain('Active Task');
  });
});
```

## Testing OnPush Components

OnPush components require explicit change detection:

```typescript
@Component({
  changeDetection: ChangeDetectionStrategy.OnPush,
  template: `<span>{{ data().name }}</span>`,
})
export class OnPushComponent {
  data = input.required<{ name: string }>();
}

describe('OnPushComponent', () => {
  it('should update when input signal changes', () => {
    const fixture = TestBed.createComponent(OnPushComponent);
    
    // Set input using setInput (for signal inputs)
    fixture.componentRef.setInput('data', { name: 'Initial' });
    fixture.detectChanges();
    
    expect(fixture.nativeElement.textContent).toContain('Initial');
    
    // Update input
    fixture.componentRef.setInput('data', { name: 'Updated' });
    fixture.detectChanges();
    
    expect(fixture.nativeElement.textContent).toContain('Updated');
  });
});
```

## Testing Services

### Basic Service Test

```typescript
import { TestBed } from '@angular/core/testing';

@Injectable({ providedIn: 'root' })
export class CounterService {
  private _count = signal(0);
  readonly count = this._count.asReadonly();
  
  increment() {
    this._count.update(c => c + 1);
  }
  
  reset() {
    this._count.set(0);
  }
}

describe('CounterService', () => {
  let service: CounterService;
  
  beforeEach(() => {
    TestBed.configureTestingModule({});
    service = TestBed.inject(CounterService);
  });
  
  it('should increment count', () => {
    expect(service.count()).toBe(0);
    
    service.increment();
    expect(service.count()).toBe(1);
    
    service.increment();
    expect(service.count()).toBe(2);
  });
  
  it('should reset count', () => {
    service.increment();
    service.increment();
    
    service.reset();
    
    expect(service.count()).toBe(0);
  });
});
```

### Service with Dependencies

```typescript
@Injectable({ providedIn: 'root' })
export class UserService {
  private http = inject(HttpClient);
  
  getUser(id: string) {
    return this.http.get<User>(`/api/users/${id}`);
  }
}

describe('UserService', () => {
  let service: UserService;
  let httpMock: HttpTestingController;
  
  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [
        provideHttpClient(),
        provideHttpClientTesting(),
      ],
    });
    
    service = TestBed.inject(UserService);
    httpMock = TestBed.inject(HttpTestingController);
  });
  
  afterEach(() => {
    httpMock.verify(); // Verify no outstanding requests
  });
  
  it('should fetch user by id', () => {
    const mockUser: User = { id: '1', name: 'Test User' };
    
    service.getUser('1').subscribe(user => {
      expect(user).toEqual(mockUser);
    });
    
    const req = httpMock.expectOne('/api/users/1');
    expect(req.request.method).toBe('GET');
    req.flush(mockUser);
  });
});
```

## Mocking Dependencies

### Using Jasmine Spies

```typescript
describe('ComponentWithDependency', () => {
  let userServiceSpy: jasmine.SpyObj<UserService>;
  
  beforeEach(async () => {
    userServiceSpy = jasmine.createSpyObj('UserService', ['getUser', 'updateUser']);
    userServiceSpy.getUser.and.returnValue(of({ id: '1', name: 'Test' }));
    
    await TestBed.configureTestingModule({
      imports: [UserProfileComponent],
      providers: [
        { provide: UserService, useValue: userServiceSpy },
      ],
    }).compileComponents();
  });
  
  it('should call getUser on init', () => {
    const fixture = TestBed.createComponent(UserProfileComponent);
    fixture.detectChanges();
    
    expect(userServiceSpy.getUser).toHaveBeenCalledWith('1');
  });
});
```

### Mock Signal-Based Service

```typescript
// Create mock with signal
const mockAuthService = {
  user: signal<User | null>(null),
  isAuthenticated: computed(() => mockAuthService.user() !== null),
  login: jasmine.createSpy('login'),
  logout: jasmine.createSpy('logout'),
};

beforeEach(async () => {
  await TestBed.configureTestingModule({
    imports: [ProtectedComponent],
    providers: [
      { provide: AuthService, useValue: mockAuthService },
    ],
  }).compileComponents();
});

it('should show content when authenticated', () => {
  mockAuthService.user.set({ id: '1', name: 'Test User' });
  
  const fixture = TestBed.createComponent(ProtectedComponent);
  fixture.detectChanges();
  
  expect(fixture.nativeElement.querySelector('.protected-content')).toBeTruthy();
});
```

## Testing Inputs and Outputs

```typescript
@Component({
  selector: 'app-item',
  template: `
    <div (click)="select()">{{ item().name }}</div>
  `,
})
export class ItemComponent {
  item = input.required<Item>();
  selected = output<Item>();
  
  select() {
    this.selected.emit(this.item());
  }
}

describe('ItemComponent', () => {
  it('should emit selected event on click', () => {
    const fixture = TestBed.createComponent(ItemComponent);
    const item: Item = { id: '1', name: 'Test Item' };
    
    fixture.componentRef.setInput('item', item);
    fixture.detectChanges();
    
    // Subscribe to output
    let emittedItem: Item | undefined;
    fixture.componentInstance.selected.subscribe(i => emittedItem = i);
    
    // Trigger click
    fixture.nativeElement.querySelector('div').click();
    
    expect(emittedItem).toEqual(item);
  });
});
```

## Testing Async Operations

### Using fakeAsync

```typescript
import { fakeAsync, tick, flush } from '@angular/core/testing';

it('should debounce search', fakeAsync(() => {
  const fixture = TestBed.createComponent(SearchComponent);
  fixture.detectChanges();
  
  // Type in search
  fixture.componentInstance.query.set('test');
  
  // Advance time for debounce
  tick(300);
  fixture.detectChanges();
  
  expect(fixture.componentInstance.results().length).toBeGreaterThan(0);
  
  // Flush any remaining timers
  flush();
}));
```

### Using waitForAsync

```typescript
import { waitForAsync } from '@angular/core/testing';

it('should load data', waitForAsync(() => {
  const fixture = TestBed.createComponent(DataComponent);
  fixture.detectChanges();
  
  fixture.whenStable().then(() => {
    fixture.detectChanges();
    expect(fixture.componentInstance.data()).toBeDefined();
  });
}));
```

## Testing HTTP Resources

```typescript
@Component({
  template: `
    @if (userResource.isLoading()) {
      <p>Loading...</p>
    } @else if (userResource.hasValue()) {
      <p>{{ userResource.value().name }}</p>
    }
  `,
})
export class UserComponent {
  userId = signal('1');
  userResource = httpResource<User>(() => `/api/users/${this.userId()}`);
}

describe('UserComponent', () => {
  let httpMock: HttpTestingController;
  
  beforeEach(async () => {
    await TestBed.configureTestingModule({
      imports: [UserComponent],
      providers: [
        provideHttpClient(),
        provideHttpClientTesting(),
      ],
    }).compileComponents();
    
    httpMock = TestBed.inject(HttpTestingController);
  });
  
  it('should display user name after loading', () => {
    const fixture = TestBed.createComponent(UserComponent);
    fixture.detectChanges();
    
    // Initially loading
    expect(fixture.nativeElement.textContent).toContain('Loading');
    
    // Respond to request
    const req = httpMock.expectOne('/api/users/1');
    req.flush({ id: '1', name: 'John Doe' });
    fixture.detectChanges();
    
    expect(fixture.nativeElement.textContent).toContain('John Doe');
  });
});
```

## Vitest vs Jasmine Comparison

| Feature | Vitest | Jasmine/Karma |
|---------|--------|---------------|
| Speed | Faster (native ESM) | Slower |
| Watch mode | Instant feedback | Slower rebuilds |
| Mocking | `vi.fn()`, `vi.mock()` | `jasmine.createSpy()` |
| Assertions | `expect()` (Chai-style) | `expect()` (Jasmine) |
| UI | Built-in UI mode | Karma browser |
| Config | `angular.json` | `karma.conf.js` |

### Migration from Jasmine to Vitest

```typescript
// Jasmine
const spy = jasmine.createSpy('callback');
spy.and.returnValue('value');
expect(spy).toHaveBeenCalledWith('arg');

// Vitest
const spy = vi.fn();
spy.mockReturnValue('value');
expect(spy).toHaveBeenCalledWith('arg');
```

```typescript
// Jasmine
spyOn(service, 'method').and.returnValue(of(data));

// Vitest
vi.spyOn(service, 'method').mockReturnValue(of(data));
```

For advanced testing patterns, see [references/testing-patterns.md](references/testing-patterns.md).