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EnvModel: Returns error 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​

  • Application Bootstrap: Ensures bootstrapNestApplication validates environment models
  • Exit Code Handling: Verifies the process exits with code 1 on validation failure
  • EnvModel Integration: Tests environment validation in full application context
  • Process Exit Mocking: Confirms proper handling of process.exit during tests

GitHub Reference​

Setup Code​

The test mocks process.exit to prevent actual process termination during testing:

import { Injectable } from '@nestjs/common';
import { IsNotEmpty } from 'class-validator';
import { EnvModel, EnvModelProperty } from '../env-model/decorators';
import { DefaultNestApplicationInitializer } from '../modules/system/default-nest-application/default-nest-application-initializer';
import { createNestModule } from '../nest-module/utils';
import { bootstrapNestApplication } from './utils';

// Mock process.exit
let originalExit: any;
let exitStatus: any;

beforeAll(() => {
  originalExit = process.exit;
  process.exit = (status) => {
    exitStatus = status;
    return null as never;
  };
});

afterAll(() => {
  process.exit = originalExit;
});

afterEach(() => {
  exitStatus = null;
});

Test Code​

it('should return error if option of env not set', async () => {
  @EnvModel()
  class AppEnv {
    @EnvModelProperty()
    @IsNotEmpty()
    option!: string;
  }

  const { AppModule } = createNestModule({
    moduleName: 'AppModule',
    environmentsModel: AppEnv,
  });

  await bootstrapNestApplication({
    project: { name: 'TestApp', description: 'Test application' },
    modules: {
      system: [DefaultNestApplicationInitializer.forRoot()],
      feature: [AppModule.forRoot()],
    },
  });

  expect(exitStatus).toEqual(1);
});

What This Test Does​

  1. Mocks process.exit to capture exit codes without terminating the test process
  2. Creates an EnvModel with a required option field
  3. Creates a NestModule using createNestModule with the EnvModel
  4. Attempts to bootstrap the application without setting the required environment variable
  5. Expects the bootstrap to trigger process.exit(1) due to validation failure
  6. Verifies exit code is 1, indicating application failed to start

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.