Connect to a Postgres Database in E2E NestJS: A Step-by-Step Guide

Are you tired of dealing with tedious database connections in your NestJS application? Do you want to learn how to seamlessly integrate a Postgres database with your E2E (End-to-End) testing framework? Look no further! In this comprehensive guide, we’ll take you by the hand and walk you through the process of connecting to a Postgres database in E2E NestJS.

What is E2E Testing in NestJS?

Why Postgres?

So, why choose Postgres as your database of choice? Well, Postgres is an incredibly powerful, open-source, and widely-used relational database management system. Its robust feature set, scalability, and security make it an excellent choice for building robust and scalable applications. Plus, NestJS provides out-of-the-box support for Postgres, making it a smooth and efficient integration process.

Prerequisites

• Node.js (version 14 or higher)
• @nestjs/cli (version 8 or higher)
• Postgres (version 12 or higher)
• typeorm (version 0.2.41 or higher)

Step 1: Create a New NestJS Project

Let’s start by creating a new NestJS project using the following command:

$ nest new my-nest-app

Follow the prompts to set up your project, and once you’ve completed the process, navigate to the project directory:

$ cd my-nest-app

Step 2: Install Required Dependencies

Next, we need to install the required dependencies for TypeORM and Postgres. Run the following commands:

$ npm install --save @nestjs/typeorm typeorm postgres

Step 3: Configure TypeORM

Create a new file called `typeorm.config.js` in the root of your project:

// typeorm.config.js
import { TypeOrmModuleOptions } from '@nestjs/typeorm';

export const typeOrmConfig: TypeOrmModuleOptions = {
  type: 'postgres',
  url: 'localhost:5432',
  username: 'my_username',
  password: 'my_password',
  database: 'my_database',
  entities: [__dirname + '/../**/*.entity{.ts,.js}'],
  synchronize: true,
};

Update the configuration to match your Postgres credentials and database settings.

Step 4: Create an Entity

Create a new file called `user.entity.ts` in the `src/entities` directory:

// user.entity.ts
import { Entity, Column, PrimaryGeneratedColumn } from 'typeorm';

@Entity()
export class User {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  name: string;

  @Column()
  email: string;
}

This entity represents a simple `User` table with `id`, `name`, and `email` columns.

Step 5: Create a Repository

Create a new file called `user.repository.ts` in the `src/repositories` directory:

// user.repository.ts
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import { User } from './user.entity';

@Injectable()
export class UserRepository {
  constructor(
    @InjectRepository(User)
    private readonly userRepository: Repository,
  ) {}

  async findAll(): Promise {
    return this.userRepository.find();
  }

  async findOne(id: number): Promise {
    return this.userRepository.findOne(id);
  }

  async create(user: User): Promise {
    return this.userRepository.save(user);
  }

  async update(id: number, user: User): Promise {
    return this.userRepository.update(id, user);
  }

  async delete(id: number): Promise {
    return this.userRepository.delete(id);
  }
}

This repository provides basic CRUD (Create, Read, Update, Delete) operations for the `User` entity.

Step 6: Create a Service

Create a new file called `user.service.ts` in the `src/services` directory:

// user.service.ts
import { Injectable } from '@nestjs/common';
import { UserRepository } from './user.repository';

@Injectable()
export class UserService {
  constructor(private readonly userRepository: UserRepository) {}

  async findAll(): Promise {
    return this.userRepository.findAll();
  }

  async findOne(id: number): Promise {
    return this.userRepository.findOne(id);
  }

  async create(user: User): Promise {
    return this.userRepository.create(user);
  }

  async update(id: number, user: User): Promise {
    return this.userRepository.update(id, user);
  }

  async delete(id: number): Promise {
    return this.userRepository.delete(id);
  }
}

This service layer acts as an intermediary between the controller and the repository, providing a layer of abstraction for business logic.

Step 7: Create a Controller

Create a new file called `user.controller.ts` in the `src/controllers` directory:

// user.controller.ts
import { Controller, Get, Post, Body, Param, Put, Delete } from '@nestjs/common';
import { UserService } from './user.service';

@Controller('users')
export class UserController {
  constructor(private readonly userService: UserService) {}

  @Get()
  async findAll(): Promise {
    return this.userService.findAll();
  }

  @Get(':id')
  async findOne(@Param('id') id: number): Promise {
    return this.userService.findOne(id);
  }

  @Post()
  async create(@Body() user: User): Promise {
    return this.userService.create(user);
  }

  @Put(':id')
  async update(@Param('id') id: number, @Body() user: User): Promise {
    return this.userService.update(id, user);
  }

  @Delete(':id')
  async delete(@Param('id') id: number): Promise {
    return this.userService.delete(id);
  }
}

This controller handles HTTP requests and delegates tasks to the service layer.

Step 8: Configure E2E Testing

Create a new file called `app.e2e-spec.ts` in the `src` directory:

// app.e2e-spec.ts
import { Test, TestingModule } from '@nestjs/testing';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { TypeOrmModule } from '@nestjs/typeorm';
import { UserController } from './user.controller';

describe('AppController (e2e)', () => {
  let app: TestingModule;

  beforeEach(async () => {
    app = await Test.createTestingModule({
      imports: [TypeOrmModule.forRoot(typeOrmConfig)],
      controllers: [AppController, UserController],
      providers: [AppService],
    }).compile();
  });

  it('should create a new user', async () => {
    constUserController = app.get(UserController);
    const user = await UserController.create({ name: 'John Doe', email: 'john.doe@example.com' });
    expect(user).toHaveProperty('id');
  });

  it('should retrieve all users', async () => {
    constUserController = app.get(UserController);
    const users = await UserController.findAll();
    expect(users).toBeInstanceOf(Array);
  });

  // Add more test cases as needed
});

This E2E test suite uses Jest to create a mocked application instance, which allows us to test the entire application, including the database connection, in isolation.

Conclusion

And that’s it! You’ve successfully connected to a Postgres database in E2E NestJS. By following this step-by-step guide, you’ve set up a robust and scalable application with a robust database connection. Remember to tailor this example to your specific use case and requirements.

Keyword	Description
E2E Testing	End-to-End testing approach that involves testing an application from start to finish, simulating real-user interactions.
Postgres	A powerful, open-source, and widely-used relational database managementHere are the 5 Questions and Answers about “Connect to a postgres database in e2e NestJS”: Frequently Asked Question Get ready to dive into the world of NestJS and PostgreSQL! How do I install the required packages to connect to a PostgreSQL database in NestJS? To connect to a PostgreSQL database in NestJS, you’ll need to install the `@nestjs/typeorm` package, which provides a convenient way to interact with your database. Run the following command in your terminal: `npm install @nestjs/typeorm pg`. This will install the required packages, including the `pg` package, which is the PostgreSQL driver for Node.js. How do I configure the database connection in my NestJS application? To configure the database connection, you’ll need to create a `typeorm` configuration file in your NestJS project. This file typically goes in the `src` directory and is named `typeorm.config.ts`. In this file, you’ll specify the database connection details, such as the database name, username, password, and host. For example: `module.exports = { type: ‘postgres’, url: ‘localhost’, username: ‘your_username’, password: ‘your_password’, database: ‘your_database’, entities: [__dirname + ‘/../**/*.entity{.ts,.js}’], synchronize: true };` How do I create a database entity in NestJS? To create a database entity in NestJS, you’ll need to create a new file in the `src/entities` directory. For example, let’s create a `user.entity.ts` file. In this file, you’ll define the entity using the `@Entity` decorator and specify the database columns using the `@Column` decorator. For example: `@Entity() export class User { @PrimaryGeneratedColumn() id: number; @Column() name: string; @Column() email: string; }` How do I use the database connection in my NestJS service? To use the database connection in your NestJS service, you’ll need to inject the `EntityManager` using the `@InjectRepository` decorator. For example: `@InjectRepository(User) private readonly userRepository: Repository;` Then, you can use the `userRepository` to perform database operations, such as creating a new user: `const user = this.userRepository.create({ name: ‘John Doe’, email: ‘johndoe@example.com’ });` How do I test my database connection in a NestJS e2e test? To test your database connection in a NestJS e2e test, you’ll need to create a test file in the `test` directory. For example, let’s create a `app.e2e-spec.ts` file. In this file, you can use the `Test` decorator to define a test suite. Then, you can use the `beforeEach` hook to create a test database connection. For example: `beforeEach(async () => { await createTestDataBaseConnection(); });` Finally, you can write test cases to verify that the database connection is working as expected. Share this: Add Comment Exit mobile version