Testing

Priority: P1 (HIGH)

1. Query via Component Harnesses

• Always use ComponentHarness (e.g., MatButtonHarness) instead of CSS selectors — harnesses are stable across DOM changes.

See harness pattern for ComponentHarness examples.

2. Mock HTTP with HttpTestingController

• Use provideHttpClientTesting() instead of manual HttpClient mocks.
• Call expectOne, .flush(mockData), and verify() in afterEach.

See harness pattern for HttpTestingController examples.

3. Test Signal Inputs Correctly

• Use fixture.componentRef.setInput('name', value) — do NOT assign directly.
• Call fixture.detectChanges() after setInput().
• Signals update synchronously — fakeAsync is usually not needed.

4. Choose Your Test Runner

• Angular v20+ supports Vitest natively via @angular/build:unit-test. Faster, native ESM, no Karma needed.
• Jasmine/Karma still supported for existing projects.

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