Inject Typeorm Repository Into Nestjs Service For Mock Data Testing

When it comes to testing your NestJS services, having the ability to inject a TypeORM repository can be a game-changer. By doing so, you can easily mock data and create more robust tests for your application. In this guide, we will walk you through the process of injecting a TypeORM repository into a NestJS service for mock data testing.

### Why Inject TypeORM Repository?

Injecting a TypeORM repository into your NestJS service allows you to decouple your business logic from the data access layer, making it easier to test your services in isolation. With this approach, you can create mock data instances for your tests without relying on a live database connection, leading to faster and more reliable testing.

### Step 1: Set Up Your TypeORM Repository

First, make sure you have TypeORM installed in your NestJS project. If not, you can add it using npm or yarn:

Bash

npm install typeorm

Next, create your TypeORM entity and repository classes as you normally would. For example, let's say you have a `User` entity and its corresponding repository:

Typescript

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

  @Column()
  name: string;
}

Typescript

@EntityRepository(User)
export class UserRepository extends Repository {}

### Step 2: Inject the TypeORM Repository into Your Service

To inject the TypeORM repository into your NestJS service, you can use constructor injection. Import the repository class into your service file and declare it as a private property:

Typescript

import { UserRepository } from './user.repository';

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

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

  // Add other service methods here
}

### Step 3: Write Your Test Cases

Now that you have injected the TypeORM repository into your service, you can start writing test cases using Jest or any other testing framework of your choice. In your test files, you can create mock data instances and use them to test your service methods:

Typescript

describe('UserService', () =&gt; {
  let userService: UserService;

  beforeEach(async () =&gt; {
    const module: TestingModule = await Test.createTestingModule({
      providers: [UserService, UserRepository],
    }).compile();

    userService = module.get(UserService);
  });

  it('should return all users', async () =&gt; {
    const users = await userService.findAll();

    expect(users).toHaveLength(2);
  });

  // Add more test cases here
});

### Conclusion

By injecting a TypeORM repository into your NestJS service for mock data testing, you can improve the quality of your codebase and make testing a more efficient process. This approach helps you write tests that are easier to maintain and less reliant on external dependencies. Give it a try in your next NestJS project and see the difference it makes in your testing workflow!

Related posts:

Contact Info