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Overview

Angular CLI projects use Karma as the default test runner, paired with Jasmine as the testing framework. Test files follow the *.spec.ts naming convention and are co-located with the source files they test. When you run ng test, Karma launches a browser, compiles all *.spec.ts files, and reports results both in the terminal and in the browser window.

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Running unit tests

ng test
In watch mode (ng test), Karma re-runs affected tests automatically whenever you save a source file. This is the recommended mode during active development. When --code-coverage is passed, a coverage report is generated in the coverage/ directory. Open coverage/index.html in a browser to explore which lines, branches, and functions are covered.

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Writing unit tests

Angular provides TestBed for configuring test modules and ComponentFixture for interacting with components in isolation. 
import { ComponentFixture, TestBed } from '@angular/core/testing';
import { CoursesComponent } from './courses.component';

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

  beforeEach(async () => {
    await TestBed.configureTestingModule({
      declarations: [CoursesComponent],
    }).compileComponents();

    fixture = TestBed.createComponent(CoursesComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

  it('should create', () => {
    expect(component).toBeTruthy();
  });
});
For async operations, use Angular’s fakeAsync and tick utilities, or async/await with fixture.whenStable().

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End-to-end tests

End-to-end (E2E) tests simulate real user interactions across the full application stack. 
ng e2e
Angular CLI does not include an E2E framework by default. You must install and configure a framework such as Cypress or Playwright separately before ng e2e will work. Follow the setup instructions for your chosen framework to register it as the E2E builder in angular.json.

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Code coverage

Aim for high coverage in services and utility functions, where business logic is concentrated. For components, focus on testing the behavior visible to users rather than implementation details. A coverage report showing which branches are untested is more actionable than a single percentage target.

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