jsschools
Project Structure

Where Files Live in a Nest App

Project Structure

Tour the default Nest project layout and the conventions the framework pushes you toward.

4 min read Level 1/5 #nestjs#structure#project
What you'll learn
  • Identify the role of main.ts, app.module.ts, app.controller.ts, app.service.ts
  • Understand .spec.ts colocation
  • Read nest-cli.json

A fresh Nest project has more files than a plain Node script, but every one has a clear job. Knowing the layout makes the rest of the framework click.

The src/ Tree

src/
  main.ts                  # entry point — creates the app and listens
  app.module.ts            # root module — composes the app
  app.controller.ts        # sample HTTP controller
  app.controller.spec.ts   # unit test for the controller
  app.service.ts           # sample service (business logic)

main.ts is where your app boots:

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  await app.listen(3000);
}
bootstrap();

app.module.ts is the root module — it lists which controllers and services belong to the app:

import { Module } from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';

@Module({
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {}

Tests Live Next to Their Subject

Unit tests are colocated as *.spec.ts files. End-to-end tests live in a separate test/ folder at the project root, with their own Jest config so they can spin up real HTTP servers.

test/
  app.e2e-spec.ts
  jest-e2e.json

nest-cli.json

This file tells the CLI where source lives, which assets to copy at build time, and which schematics defaults to use. The defaults are sane — you rarely edit it until you split into a monorepo.

{
  "$schema": "https://json.schemastore.org/nest-cli",
  "collection": "@nestjs/schematics",
  "sourceRoot": "src",
  "compilerOptions": {
    "deleteOutDir": true
  }
}

Scripts in package.json

npm run start:dev, npm test, npm run test:e2e, npm run build. They all delegate to the Nest CLI or Jest with the right flags.

Modules — Nest's Composition Unit →