Test Generation

Overview

Generate comprehensive tests following TDD principles and project testing standards. Runs in isolated test-engineer context with pre-loaded testing conventions.

Announce at start: "I'm using the test-generation skill to create tests for [feature/component]."

The Process

Step 1: Specify Test Requirements

Provide clear requirements to test-engineer:

/test-generation

Feature: JWT token validation middleware

Behaviors:
1. Valid token → allow request
2. Expired token → reject with 401
3. Invalid signature → reject with 401
4. Missing token → reject with 401

Coverage: All critical paths

Testing Standards (pre-loaded):
- Framework: vitest
- Mocks: vi.mock()
- Structure: AAA pattern

Step 2: Review Test Plan

Test-engineer proposes a test plan:

## Test Plan

Behaviors:
1. Valid token
   - ✅ Positive: Allow request with valid JWT
   - ❌ Negative: Reject malformed JWT
2. Expired token
   - ✅ Positive: Normal token works
   - ❌ Negative: Expired token rejected with 401

Mocking Strategy:
- JWT verification: Mock with vi.mock()
- Request/Response: Use test doubles

Coverage Target: 95% line coverage, all critical paths

IMPORTANT: Review and approve before implementation proceeds.

Step 3: Implement Tests

Test-engineer implements following AAA pattern (Arrange-Act-Assert):

describe('JWT Middleware', () => {
  it('allows request with valid token', () => {
    // Arrange
    const req = mockRequest({ headers: { authorization: 'Bearer valid.jwt.token' } });
    
    // Act
    const result = jwtMiddleware(req);
    
    // Assert
    expect(result.authorized).toBe(true);
  });
});

Step 4: Run Self-Review

Test-engineer verifies:

• ✅ Positive AND negative tests for each behavior
• ✅ AAA pattern followed
• ✅ All external dependencies mocked
• ✅ Tests are deterministic (no flakiness)
• ✅ Standards compliance

Step 5: Run Tests

Execute test suite and verify all pass:

npm test -- jwt.middleware.test.ts

Step 6: Return Results

status: success
tests_written: 8
coverage:
  lines: 96%
  branches: 93%
  functions: 100%
behaviors_tested:
  - name: "Valid token handling"
    positive_tests: 2
    negative_tests: 2
test_results:
  passed: 8
  failed: 0
deliverables:
  - "src/auth/jwt.middleware.test.ts"

TDD Workflow

For test-driven development, invoke BEFORE implementation:

/test-generation

Write tests for user registration endpoint (not yet implemented):

Expected Behavior:
- POST /api/register with valid data → 201 + user object
- POST /api/register with duplicate email → 409 error
- POST /api/register with invalid email → 400 error

Note: Implementation does not exist. Write tests that define expected behavior.

Tests will fail initially—use them as spec to guide implementation.

Error Handling

Tests don't match project conventions:

• Main agent must pre-load .opencode/context/core/standards/tests.md

Missing edge cases:

• Specify explicitly in requirements

Flaky tests:

• Ensure all external dependencies mocked

Red Flags

If you think any of these, STOP and re-read this skill:

• "The implementation is simple enough that tests aren't needed"
• "I'll just write the happy path tests for now"
• "Mocking is too complex for this dependency"
• "I'll add tests after the feature is stable"

Common Rationalizations

Excuse	Reality
"It's too simple to break"	Simple code breaks in simple ways. Tests document the contract, not just catch bugs.
"Negative tests are obvious failures, not worth writing"	Negative tests are where bugs hide. "Obviously fails" is not the same as "correctly fails".
"Mocking this dependency is too hard"	Hard-to-mock dependencies are a design smell. Mock them anyway and note the smell.
"Tests slow down delivery"	Tests without negative cases give false confidence. False confidence slows delivery more.

Remember

• Pre-load testing standards BEFORE invoking skill
• Specify clear behaviors and acceptance criteria
• Review test plan before implementation
• Both positive AND negative tests required
• All external dependencies MUST be mocked (no real network/DB calls)
• AAA pattern (Arrange-Act-Assert) mandatory
• Tests must be deterministic (no randomness or time dependencies)

Related

• code-execution
• code-review
• context-discovery