Context
Backend services are instantiated with manual imports and tight coupling, making testing difficult and refactoring risky.
Current Limitation/Problem
Services import dependencies directly (e.g., import prisma from "../prisma"). Unit testing requires mocking entire modules. Service wiring changes require modifying every file.
Expected Outcome
A lightweight dependency injection container where services declare their dependencies via constructor injection. Services become testable with mock injection.
Acceptance Criteria
- Implement DI container (tsyringe or awilix)
- Register all services in container with lifecycle management (singleton, scoped, transient)
- Services receive dependencies via constructor injection
- Controllers and middleware resolve services from container
- Unit tests inject mock dependencies
- Feature flag: opt-in old vs new injection pattern during migration
- DI container configuration validation on startup
- Performance: injection overhead <1ms per resolution
- Migration guide and codemod for service files
Technical Scope
backend/src/di/ - DI container configurationbackend/src/di/container.ts - container setup- Registration of existing services (PaymentService, WalletService, etc.)
- Refactor service constructors to accept dependencies
backend/src/di/modules/ - per-domain module registrations- Edge cases: circular dependencies, async initialization, request-scoped services
Context
Backend services are instantiated with manual imports and tight coupling, making testing difficult and refactoring risky.
Current Limitation/Problem
Services import dependencies directly (e.g.,
import prisma from "../prisma"). Unit testing requires mocking entire modules. Service wiring changes require modifying every file.Expected Outcome
A lightweight dependency injection container where services declare their dependencies via constructor injection. Services become testable with mock injection.
Acceptance Criteria
Technical Scope
backend/src/di/- DI container configurationbackend/src/di/container.ts- container setupbackend/src/di/modules/- per-domain module registrations