Courses API — NestJS + TypeORM

REST API for managing courses and their tags, built to learn NestJS in depth: modules and dependency injection, DTO validation, TypeORM relations and migrations, and both unit and end-to-end testing.

Stack: NestJS 11 · TypeScript · TypeORM · PostgreSQL · class-validator · Jest · Supertest

Study project based on a NestJS course, extended and documented as I went. Focus is on the patterns, not on the domain.

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What it does

• Full CRUD for courses (name, description, tags)
• Many-to-many relation between courses and tags through a pivot table
• Tags are sent as plain names (["nestjs", "typescript"]); existing tags are reused and new ones are created automatically
• Request validation with a global ValidationPipe — unknown fields are rejected (whitelist + forbidNonWhitelisted) and payloads are transformed into DTO instances
• Proper HTTP semantics: 404 for unknown IDs, 204 on delete

What I practiced

Topic	Where
Modules, controllers, providers and DI	src/courses/
DTOs with class-validator and PartialType for updates	src/courses/dto/
Entities with UUID keys and @ManyToMany + cascade	src/courses/entities/
Async DB config from environment with @nestjs/config	src/database/database.module.ts
Versioned migrations (synchronize: false)	src/migrations/, src/database/orm-cli-config.ts
Unit tests with mocked repositories	src/courses/courses.service.spec.ts
E2E tests against a real database with Supertest	src/courses/courses.controller.e2e-spec.ts
Git flow with develop branch and pull requests	commit history

Running locally

Requirements: Node.js 20+ and PostgreSQL.

git clone https://github.com/GabRfg/nest-api.git
cd nest-api
npm install

Create a .env file:

DB_HOST=localhost
DB_PORT=5432
DB_USER=postgres
DB_PASS=your_password
DB_NAME=courses
PORT=3000

Run the migrations, then start the app:

npx ts-node -r tsconfig-paths/register ./node_modules/typeorm/cli.js migration:run -d src/database/orm-cli-config.ts
npm run start:dev

Endpoints

Method	Route	Description
GET	/courses	List courses with their tags
GET	/courses/:id	Get one course
POST	/courses	Create a course
PUT	/courses/:id	Update a course (partial)
DELETE	/courses/:id	Delete a course (204)

POST /courses
{
  "name": "NestJS Fundamentals",
  "description": "Modules, DI and TypeORM",
  "tags": ["nestjs", "typescript"]
}

Tests

npm run test      # unit tests (repositories mocked)
npm run test:e2e  # end-to-end, hits the database in .env
npm run test:cov  # coverage report

The e2e suite uses the same DB_* variables as the app — point them to a disposable database before running it.

Next steps

• Docker Compose with PostgreSQL for one-command setup
• Separate test database configuration
• Pagination on GET /courses
• Swagger / OpenAPI documentation