Testing

Core Principles

1. Prefer vi.spyOn over vi.mock - More targeted, easier to maintain
2. Tests must pass type check - Run bun run type-check after writing tests
3. After 1-2 failed fix attempts, stop and ask for help
4. Test behavior, not implementation details

Basic Test Structure

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

beforeEach(() => {
  vi.clearAllMocks();
});

afterEach(() => {
  vi.restoreAllMocks();
});

describe('ModuleName', () => {
  describe('functionName', () => {
    it('should handle normal case', () => {
      // Arrange → Act → Assert
    });
  });
});

Mock Patterns

// ✅ Spy on direct dependencies
vi.spyOn(messageService, 'createMessage').mockResolvedValue('id');

// ✅ Use vi.stubGlobal for browser APIs
vi.stubGlobal('Image', mockImage);
vi.spyOn(URL, 'createObjectURL').mockReturnValue('blob:mock');

// ❌ Avoid mocking entire modules globally
vi.mock('@/services/chat'); // Too broad

Detailed Guides

See references/ for specific testing scenarios:

• Database Model testing: references/db-model-test.md
• Electron IPC testing: references/electron-ipc-test.md
• Zustand Store Action testing: references/zustand-store-action-test.md
• Agent Runtime E2E testing: references/agent-runtime-e2e.md
• Desktop Controller testing: references/desktop-controller-test.md

Fixing Failing Tests — Optimize or Delete?

When tests fail due to implementation changes (not bugs), evaluate before blindly fixing:

Keep & Fix (update test data/assertions)

• Behavior tests: Tests that verify what the code does (output, side effects, user-visible behavior). Just update mock data formats or expected values.
  • Example: Tool data structure changed from { name } to { function: { name } } → update mock data
  • Example: Output format changed from Current date: YYYY-MM-DD to Current date: YYYY-MM-DD (TZ) → update expected string

Delete (over-specified, low value)

• Param-forwarding tests: Tests that assert exact internal function call arguments (e.g., expect(internalFn).toHaveBeenCalledWith(expect.objectContaining({ exact params }))) — these break on every refactor and duplicate what behavior tests already cover.
• Implementation-coupled tests: Tests that verify how the code works internally rather than what it produces. If a higher-level test already covers the same behavior, the low-level test adds maintenance cost without coverage gain.

Decision Checklist

1. Does the test verify externally observable behavior (API response, DB write, rendered output)? → Keep
2. Does the test only verify internal wiring (which function receives which params)? → Check if a behavior test already covers it. If yes → Delete
3. Is the same behavior already tested at a higher integration level? → Delete the lower-level duplicate
4. Would the test break again on the next routine refactor? → Consider raising to integration level or deleting

When Writing New Tests

• Prefer integration-level assertions (verify final output) over white-box assertions (verify internal calls)
• Use expect.objectContaining only for stable, public-facing contracts — not for internal param shapes that change with refactors
• Mock at boundaries (DB, network, external services), not between internal modules

Common Issues

1. Module pollution: Use vi.resetModules() when tests fail mysteriously
2. Mock not working: Check setup position and use vi.clearAllMocks() in beforeEach
3. Test data pollution: Clean database state in beforeEach/afterEach
4. Async issues: Wrap state changes in act() for React hooks