clare: Instructions file for GitHub Copilot

Testing Standards (CLARE — Assertive)

CLARE requires constraint tests, not confirmation tests. Every test file must enforce invariants — things that must always be true — not just describe what the current implementation does.

The Core Distinction

// ❌ Confirmation test — describes implementation, not invariant
it('returns the user', () => {
  const user = getUser(1);
  expect(user.id).toBe(1);
});

// ✅ Constraint test — enforces an invariant
it('always returns a user matching the requested ID', () => {
  fc.assert(
    fc.property(fc.integer({ min: 1, max: 10000 }), (id) => {
      seedUser(id);
      const user = getUser(id);
      expect(user.id).toBe(id);
    })
  );
});

Rules for Every Test File

1. Name tests as invariants, not as implementations:

   • ❌ 'creates a user'
   • ✅ 'never allows duplicate emails'

2. Add at least one property-based test per critical module using fast-check (JS) or hypothesis (Python)

3. Architecture tests go in tests/architecture/ and run in verify-ci.sh; they must check structural constraints, not behavior:

   // Architecture test example
   test('all API endpoints have rate limiting', () => {
     const endpoints = loadEndpoints();
     endpoints.forEach(ep => expect(ep).toHaveRateLimiting());
   });
   

4. Schema-lock tests: For any external contract (API, event schema, proto), add a test that would fail if the schema changes unexpectedly:

   test('User API response matches expected schema', () => {
     const response = getUser(seed.userId);
     expect(response).toMatchSnapshot(); // or use Zod schema assertion
   });
   

5. Test the test — After writing tests, delete the implementation and regenerate it with AI. If tests fail, they are working. If they pass, verify the constraints are strong enough.

Property-Based Testing Quick Reference

// fast-check (TypeScript/JavaScript)
import fc from 'fast-check';

test('never creates negative balances', () => {
  fc.assert(
    fc.property(
      fc.integer({ min: 1, max: 10000 }),
      fc.integer({ min: 1, max: 10000 }),
      (initialBalance, deductAmount) => {
        fc.pre(deductAmount <= initialBalance); // precondition
        const result = deduct(initialBalance, deductAmount);
        expect(result).toBeGreaterThanOrEqual(0);
      }
    )
  );
});