Nestjs is a Node.js framework for building efficient server-side apps. It uses TypeScript and integrates class-validator for data validation. To validate DTOs, which define data shapes, you add decorators like @IsEmail() or @IsNotEmpty() to class properties. For instance, a CreateUserDto class might look like:
import { IsEmail, IsNotEmpty, IsString } from 'class-validator'; export class CreateUserDto { @IsEmail() email: string; @IsNotEmpty() @IsString() password: string; @IsNotEmpty() @IsString() name: string; } To globally apply validation, use the ValidationPipe in your main.ts:
import { ValidationPipe } from '@nestjs/common'; async function bootstrap() { const app = await NestFactory.create(AppModule); app.useGlobalPipes(new ValidationPipe()); await app.listen(3000); } bootstrap(); For testing, use class-validator's functions like plainToClass and validateSync. A Jest unit test example:
import { plainToClass } from 'class-transformer'; import { validateSync } from 'class-validator'; import { CreateUserDto } from './create-user.dto'; describe('CreateUserDto', () => { it('should be valid with valid properties', () => { const createUserDto = plainToClass(CreateUserDto, { email: 'admin@gmail.com', password: 'xxxxxxxx', name: 'Admin', }); const errors = validateSync(createUserDto); expect(errors).toHaveLength(0); }); it('should be invalid with invalid properties', () => { const createUserDto = plainToClass(CreateUserDto, { email: 'admin@gmail.com', password: 'xxxxxxxx', name: null, }); const errors = validateSync(createUserDto); expect(errors).toHaveLength(1); // Check error details... }); }); Nestjs and class-validator simplify building and testing apps by using decorators to validate data. For more info, see the official Nestjs and class-validator documentation.
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