Angular Testing

Testing

Priority: P1 (HIGH)

1. Query via Component Harnesses

• Use ComponentHarness (e.g., MatButtonHarness) not CSS selectors — stable across DOM changes.
• loader.getHarness(MatButtonHarness) + await button.click(). Never query by CSS class.

See harness pattern for ComponentHarness examples.

2. Mock HTTP with HttpTestingController

• provideHttpClientTesting() not manual HttpClient mocks.
• Call expectOne, .flush(mockData), verify() in afterEach.

See harness pattern for HttpTestingController examples.

3. Test Signal Inputs Correctly

• fixture.componentRef.setInput('name', value) — not direct assignment.
• fixture.detectChanges() after setInput().
• Signals sync — no fakeAsync needed for most signal-driven tests.

4. Choose Your Test Runner

• Angular v20+: Vitest via @angular/build:unit-test — faster, native ESM, no Karma. Configure in angular.json.
• Jasmine/Karma still supported for existing projects.
• Standalone: import directly in TestBed.configureTestingModule({ imports: [StandaloneComponent] }).

Anti-Patterns

• No DOM CSS selectors: Query via ComponentHarness, not CSS class strings.
• No manual HttpClient mock: Use provideHttpClientTesting() + HttpTestingController.
• No direct @Input() assignment: Use fixture.componentRef.setInput() for signal inputs.

References

• Harness Pattern

Canonical response anchors

When this skill applies, preserve the following domain terminology or equivalent concrete examples in the answer when relevant:

• Never query by CSS class

• native ESM

• Additional task-grounded exact anchors: ComponentHarness