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EnvModel: Returns error message if option of env not set

Overview​

These tests validate nestjs-mod EnvModel: environment variable reading, required field validation, and DI value propagation into services.

What We're Testing​

  • Error Message Format: Ensures error messages include source tracking information
  • Dual Source Display: Verifies both object property and process.env variable names are shown
  • Validation Details: Confirms the validation constraint is included in the message

GitHub Reference​

Setup Code​

import { DynamicModule, Module } from '@nestjs/common';
import { Test } from '@nestjs/testing';
import { IsNotEmpty } from 'class-validator';
import { EnvModel, EnvModelProperty } from './decorators';
import { envTransform } from './utils';

@EnvModel()
class AppEnv {
  @EnvModelProperty()
  @IsNotEmpty()
  option!: string;
}

@Module({ providers: [AppEnv] })
class AppModule {
  static forRoot(env: Partial<AppEnv>): DynamicModule {
    return {
      module: AppModule,
      providers: [
        {
          provide: `${AppEnv.name}_loader`,
          useFactory: async (emptyAppEnv: AppEnv) => {
            if (env.constructor !== Object) {
              Object.setPrototypeOf(emptyAppEnv, env);
            }
            const obj = await envTransform({
              model: AppEnv,
              data: env,
            });
            Object.assign(emptyAppEnv, obj.data);
          },
          inject: [AppEnv],
        },
      ],
    };
  }
}

Test Code​

it('should return error message if option of env not set', async () => {
  try {
    await Test.createTestingModule({
      imports: [AppModule.forRoot({})],
    }).compile();
  } catch (err: any) {
    expect(err.message).toEqual(`obj['option'],process.env['OPTION']-isNotEmpty`);
  }
});

What This Test Does​

  1. Creates an EnvModel with a required option field
  2. Attempts to initialize the module without providing the environment variable
  3. Catches the validation error
  4. Verifies the error message contains a specific format: obj['option'],process.env['OPTION']-isNotEmpty

Key Points​

  • This test locks the behavior contract of the target nestjs-mod block in this scenario.
  • Assertions protect integration boundaries and reduce regression risk when internals evolve.