Testing infrastructure — unit and integration test setup

[Xaxxoo]

OverviewnEstablishes the testing foundation that all modules build on. Provides test utilities, mock factories, database helpers, and coverage reporting. Every module must hit 80% coverage before merging.nn## Acceptance Criterian- [ ] jest.config.ts: configure moduleNameMapper for path aliases, collectCoverageFrom for all service files, coverageThreshold (statements/branches/functions/lines all >= 80%), testEnvironment noden- [ ] test/ directory structure: test/unit/ for unit tests (mocked deps), test/integration/ for tests against real Postgres/Redisn- [ ] test/helpers/db.helper.ts: createTestDataSource() — creates TypeORM DataSource connecting to test Postgres; clearDatabase() — truncates all tables between tests; closeDatabase() — closes connectionn- [ ] test/helpers/auth.helper.ts: createTestUser(overrides?) — inserts a User row and returns it with a valid JWT access token; createTestAdmin() — same for admin rolen- [ ] test/helpers/mock.factory.ts: factory functions for all entities: mockUser(), mockWallet(), mockTransfer(), mockPayLink() etc. — return valid entity objects with sensible defaultsn- [ ] test/helpers/request.helper.ts: wraps supertest with auth header injection: authedRequest(app, token).get('/path')n- [ ] Integration test example (Transfers): create two users → provision wallets (mocked Soroban) → POST /transfers → verify Transfer record created + Transaction records for both usersn- [ ] GitHub Actions: pnpm test:cov runs with coverage; post coverage summary as PR comment using jest-coverage-comment actionn- [ ] pnpm test:e2e: runs integration tests against real Postgres (Docker); separate from unit tests in CIn- [ ] Document testing patterns in TESTING.md: when to use unit vs integration, how to mock SorobanService, how to use test helpers

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Congratulations, @akargi! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on March 30, 2026.

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