sdcorejs-testing-integration-nestjs

NestJS integration tests with real dependency injection use `Test.createTestingModule` to wire actual providers and a pg-mem TypeORM DataSource to execute real database queries, validating service logic without the HTTP layer.

pg-mem provides an in-memory Postgres database for TypeORM, enabling fast transaction rollback testing by validating real SQL constraints and multi-write rollback semantics against a real DataSource without persistent state.

Testing NestJS repository logic without mocks requires booting a real DI container alongside a pg-mem DataSource, allowing you to assert observable database outcomes and error paths like ConflictException or NotFoundException directly.

Yes, you can test NestJS service business logic and permission guards without the HTTP server by using `Test.createTestingModule` to bootstrap real DI wiring and asserting behavior against a pg-mem TypeORM DataSource.

You isolate NestJS integration tests using minimal per-test seeding and teardown routines, ensuring each test validates its database state independently without cross-test contamination from the shared pg-mem DataSource.

Mocking external APIs at the provider boundary in integration tests keeps the internal NestJS DI wiring and TypeORM repository execution paths real, ensuring deterministic tests that validate actual business workflow logic.