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EnvModel: Returns option value from service of other module

Overview​

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

What We're Testing​

  • Module Sharing: Ensures EnvModel can be exported and imported across modules
  • Cross-Module DI: Verifies dependency injection works across module boundaries
  • Environment Propagation: Tests that environment values are available in importing modules
  • Module Architecture: Validates the pattern of shared environment modules

GitHub Reference​

Setup Code​

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

@EnvModel()
class App1Env {
  @EnvModelProperty()
  @IsNotEmpty()
  option!: string;
}

@Injectable()
class App1Service {
  constructor(private readonly appEnv: App1Env) {}

  getEnv() {
    return this.appEnv;
  }
}

@Module({
  imports: [App1Module.forShareEnv()],
  providers: [App1Service],
  exports: [App1Service],
})
class App1Module {
  static forShareEnv(): DynamicModule {
    return {
      module: App1Module,
      providers: [App1Env],
      exports: [App1Env],
    };
  }
  
  static forRoot(env?: Partial<App1Env>): DynamicModule {
    return {
      module: App1Module,
      providers: [
        {
          provide: `${App1Env.name}_loader`,
          useFactory: async (emptyAppEnv: App1Env) => {
            if (env && env.constructor !== Object) {
              Object.setPrototypeOf(emptyAppEnv, env);
            }
            const obj = await envTransform({
              model: App1Env,
              data: env || {},
            });
            Object.assign(emptyAppEnv, obj.data);
          },
          inject: [App1Env],
        },
      ],
    };
  }
}

@Injectable()
class App2Service {
  constructor(private readonly appService: App1Service) {}

  getEnv() {
    return this.appService.getEnv();
  }
}

@Module({
  imports: [App1Module],
  providers: [App2Service],
})
class App2Module {}

Test Code​

it('should return option value from service of other module', async () => {
  process.env['OPTION'] = 'value1';

  const moduleRef: TestingModule = await Test.createTestingModule({
    imports: [App1Module.forRoot({}), App2Module],
  }).compile();
  const app2Service = moduleRef.get(App2Service);

  expect(app2Service.getEnv()).toMatchObject({ option: 'value1' });
});

What This Test Does​

  1. Sets an environment variable process.env['OPTION'] = 'value1'

  2. Creates App1Module with:

    • An EnvModel (App1Env) that reads from environment
    • A service (App1Service) that uses the env model
    • Two static methods: forRoot() for initialization and forShareEnv() for sharing

  3. Creates App2Module that:

    • Imports App1Module to access shared providers
    • Defines App2Service that depends on App1Service

  4. Initializes both modules (environment variable provides the value)

  5. Retrieves App2Service from the compiled module

  6. Verifies that App2Service can access the environment value through App1Service

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.