skill-test

name	skill-test
description	Tester mode for writing unit tests targeting 100% coverage. Use when: writing tests, adding test coverage, creating spec files, testing a component or service, Vitest, data-testid. Keywords: test, coverage, spec, vitest, unit test.
argument-hint	File or component to test (e.g., auth.service.ts)

Test — Tester Mode

When to Use

• The user asks to write or update unit tests for a file, service, or component
• A new feature was implemented and needs test coverage
• The user says "test", "coverage", "spec", "unit test"

Role

Act as a Test Engineer targeting 100% branch and line coverage, following all project testing conventions from .github/copilot-instructions.md.

Procedure

1. Read .github/copilot-instructions.md — especially sections 12 (Unit tests) and the code review checklist
2. Read the target file to understand all branches, signals, computed values, and public methods
3. Read existing spec file if it exists (update it, don't replace it)
4. Write tests following these mandatory patterns:

Test Structure

import { vi, type Mock } from 'vitest';
// Use path aliases for all imports
import { MyService } from '@services/my/my.service';

describe('MyService', () => {
  // Setup with TestBed for Angular, plain instantiation for domain
  const getByTestId = (testId: string): HTMLElement | null =>
    fixture.nativeElement.querySelector(`[data-testid="${testId}"]`);

  // Group tests logically
  describe('method or behavior', () => {
    it('should ...', () => { ... });
  });

  // HTML rendering tests (components only)
  describe('HTML rendering - structure', () => { ... });
  describe('HTML rendering - dynamic content', () => { ... });
  describe('HTML rendering - button states', () => { ... });
  describe('HTML rendering - accessibility', () => { ... });
});

Hard Constraints

• Vitest only — vi.fn(), vi.spyOn(), vi.mock(), Mock<T> — never Jest APIs
• No deprecated modules — no HttpClientTestingModule, use provideHttpClient()
• data-testid for all DOM queries — never query by class or tag
• Mock PyodideService and all Web Worker interactions
• Mock Dexie/IndexedDB — never use real database in tests
• Mock LoggerService and NotificationService when injected by the SUT (use vi.fn() for each method)
• Path aliases for all imports — no relative paths
• English only in describe and it blocks
• Every data-testid in the template must have a corresponding rendering test
• Test existence, tag type, disabled/enabled state, text content, and ARIA attributes

Coverage Goals

• All public methods
• All signal state transitions
• All computed derivations
• All error paths (try/catch branches)
• All @if / @for template conditions
• All button disabled/enabled states