# Testing

> Implements Test-Driven Development for this project—unit tests, integration tests with testcontainers, mocks, and regression tests. Use when writing or fixing tests, reproducing bugs with tests, or improving coverage. Use when this capability is needed.

- Skill: `tomevault-io/testing-47` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/testing-47`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/testing-47/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/testing-47

---


# Testing Skill

## When to use

- Writing unit or integration tests (Go or frontend)
- Writing E2E/API integration tests in `test/` folder with BDD stage patterns
- Applying TDD: failing test first, then implementation, then refactor
- Reproducing a bug with a test before fixing it
- Creating or updating bug reports when not fixing immediately
- Improving or verifying test coverage

## Test Structure Pattern

**Critical Rule**: Main test functions must contain subtests.

### Go Tests
- **Main test functions** (`TestXxx`) **MUST** contain one or more subtests using `t.Run`
- Each test case should be a subtest within the main test function
- Group related scenarios as subtests within the same main test function
- Use separate main test functions for different behaviors or distinct test groups

```go
// ✅ GOOD: Main function contains subtests
func TestNewEmail_WithInvalidInput_ReturnsError(t *testing.T) {
    t.Run("returns error for invalid email format", func(t *testing.T) {
        // test case
    })
    t.Run("returns error for empty string", func(t *testing.T) {
        // test case
    })
}
```

### Frontend Tests
- **Main test suites** should use `describe` blocks to organize related test cases
- Each `test` or `it` block should test one specific behavior
- Group related test cases within the same `describe` block

```typescript
// ✅ GOOD: Main describe block contains multiple test cases
describe('LoginPage', () => {
  test('user can submit login form', async () => { /* ... */ });
  test('displays error when email is invalid', async () => { /* ... */ });
});
```

## References

| File | Purpose |
|------|---------|
| [.cursor/rules/go-testing-practices.mdc](.cursor/rules/go-testing-practices.mdc) | Go testing (testify, t.Run subtests pattern, unit tests with mocks, integration tests with testcontainers), test naming, coverage, test data factories |
| [.cursor/rules/frontend-testing-practices.mdc](.cursor/rules/frontend-testing-practices.mdc) | Frontend testing (React Testing Library, describe/test blocks, MSW), build verification, TypeScript compilation checks |
| [.cursor/rules/test-driven-development.mdc](.cursor/rules/test-driven-development.mdc) | TDD core principles, Iron Law, verification checklist, red flags |
| [.cursor/skills/tdd-workflow/SKILL.md](.cursor/skills/tdd-workflow/SKILL.md) | Detailed TDD workflow with examples, common rationalizations, bug fix walkthrough |
| [.cursor/rules/e2e-testing-standards.mdc](.cursor/rules/e2e-testing-standards.mdc) | E2E tests in test/ folder: Given-When-Then architecture, stage files (*_test_stage.go), functional options, file organization |
| [.cursor/rules/e2e-test-overview.mdc](.cursor/rules/e2e-test-overview.mdc) | Quick reference for E2E BDD pattern, when to use, method naming |
| [.cursor/rules/e2e-test-examples.mdc](.cursor/rules/e2e-test-examples.mdc) | 7 complete examples (POST, GET, PATCH, DELETE, auth, event-driven) |
| [.cursor/rules/testing-agent.mdc](.cursor/rules/testing-agent.mdc) | Bug handling and prioritization (critical vs low), bug report template, BUG_NNN naming, systematic testing checklist, when to fix vs when to backlog |

---
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<!-- tomevault:4.0:skill_md:2026-04-13 -->