Careeroza

Testing Strategy

The Test Pyramid for a NestJS API

/\
         /e2e\        few: whole app over HTTP (Supertest), real or test DB
        /------\
       /integr. \     some: module + real database (Testcontainers / docker)
      /----------\
     /   unit     \   many: one class, dependencies mocked, milliseconds each
    /--------------\

Command	Runs
`npm test`	Unit tests: `src/*/.spec.ts`
`npm run test:watch`	Unit tests on file change
`npm run test:cov`	Unit tests + coverage report
`npm run test:e2e`	`test/*/.e2e-spec.ts`

Why DI Makes Testing Easy

Services receive their dependencies through the constructor. In a test you pass fakes instead of the real database, payment gateway or SMS sender. No network, no database, fast and repeatable.