Vitest Testing

Test File Placement

Source location	Test location
app/composables/<name>.ts	tests/app/composables/<name>.test.ts
app/components/<Name>.vue	app/components/__tests__/<Name>.test.ts (DOM tests) OR tests/app/components/<Name>.test.ts (logic-only)
app/utils/<name>.ts	tests/app/utils/<name>.test.ts
services/<name>.ts	tests/services/<name>.test.ts
utils/<name>.ts	tests/utils/<name>.test.ts
terraform/lambda/src/<Name>/index.ts	terraform/lambda/src/<Name>/__tests__/index.test.ts

Use __tests__/ co-location only for component DOM tests and Lambda handlers. Everything else goes in the top-level tests/ mirror tree.

Environment Selection

• Default: node (composables, services, utils, Lambda handlers)
• DOM tests only: Add /** @vitest-environment happy-dom */ as the first line of the test file
• Never change vitest.config.ts environment globally

Test Writing Rules

1. Imports — always explicit: import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
2. Nuxt auto-imports — call mockNuxtImports() from tests/helpers in beforeEach for any code using useRuntimeConfig, useState, computed, ref, watch, onMounted, onUnmounted, navigateTo
3. Naming — always *.test.ts, never *.spec.ts
4. Timers — use vi.useFakeTimers() in beforeEach and vi.useRealTimers() in afterEach for async/timer tests
5. Console noise — suppress with vi.spyOn(console, 'log').mockImplementation(() => {}) in beforeEach
6. Logic extraction — prefer testing extracted logic over DOM rendering; test behavior, not templates
7. Component DOM tests — use @vue/test-utils mount() with stubbed Nuxt UI components
8. AWS service mocks — use mockSend + vi.mock('@aws-sdk/...') pattern (see references/testing-patterns.md)

What to Test (per code type)

• Composables: return values, state mutations, reactive updates, edge cases
• Components: props, emits, slot rendering, conditional rendering (via logic extraction where possible)
• Services: success path, error handling (custom error classes), edge cases (empty input, missing fields)
• Utils: pure function I/O, boundary conditions
• Lambda handlers: each resolver action, valid/invalid input, DynamoDB mock responses, error paths

Running Tests

bun run test             # Single run
bun run test:watch       # Watch mode
bun run test:coverage    # With v8 coverage report

Coverage

Coverage uses @vitest/coverage-v8. Config is in vitest.config.ts. Thresholds: lines 80%, functions 80%, branches 70%, statements 80%.

Reference

Read references/testing-patterns.md for detailed mock patterns, full templates, and real codebase examples.