testing-module.ts

import {
  HttpServer,
  INestApplication,
  INestMicroservice,
  Logger,
} from '@nestjs/common';
import { MicroserviceOptions } from '@nestjs/common/interfaces/microservices/microservice-configuration.interface';
import { NestMicroserviceOptions } from '@nestjs/common/interfaces/microservices/nest-microservice-options.interface';
import { NestApplicationContextOptions } from '@nestjs/common/interfaces/nest-application-context-options.interface';
import { NestApplicationOptions } from '@nestjs/common/interfaces/nest-application-options.interface';
import { Type } from '@nestjs/common/interfaces/type.interface';
import { loadPackage } from '@nestjs/common/utils/load-package.util';
import { NestApplication, NestApplicationContext } from '@nestjs/core';
import { ApplicationConfig } from '@nestjs/core/application-config';
import { NestContainer } from '@nestjs/core/injector/container';
import { Module } from '@nestjs/core/injector/module';

export class TestingModule extends NestApplicationContext {
  constructor(
    container: NestContainer,
    scope: Type<any>[],
    contextModule: Module,
    private readonly applicationConfig: ApplicationConfig,
  ) {
    super(container, scope, contextModule);
  }

  public createNestApplication<T extends INestApplication = INestApplication>(
    httpAdapter?: HttpServer,
    options?: NestApplicationOptions,
  ): T {
    httpAdapter = httpAdapter || this.createHttpAdapter();

    this.applyLogger(options);
    this.container.setHttpAdapter(httpAdapter);

    const instance = new NestApplication(
      this.container,
      httpAdapter,
      this.applicationConfig,
      options,
    );
    return this.createAdapterProxy<T>(instance, httpAdapter);
  }

  public createNestMicroservice(
    options: NestMicroserviceOptions & MicroserviceOptions,
  ): INestMicroservice {
    const { NestMicroservice } = loadPackage(
      '@nestjs/microservices',
      'TestingModule',
      () => require('@nestjs/microservices'),
    );
    this.applyLogger(options);
    return new NestMicroservice(
      this.container,
      options,
      this.applicationConfig,
    );
  }

  private createHttpAdapter<T = any>(httpServer?: T): HttpServer {
    const { ExpressAdapter } = loadPackage(
      '@nestjs/platform-express',
      'NestFactory',
      () => require('@nestjs/platform-express'),
    );
    return new ExpressAdapter(httpServer);
  }

  private applyLogger(options: NestApplicationContextOptions | undefined) {
    if (!options || !options.logger) {
      return;
    }
    Logger.overrideLogger(options.logger);
  }

  private createAdapterProxy<T>(app: NestApplication, adapter: HttpServer): T {
    return (new Proxy(app, {
      get: (receiver: Record<string, any>, prop: string) => {
        if (!(prop in receiver) && prop in adapter) {
          return adapter[prop];
        }
        return receiver[prop];
      },
    }) as any) as T;
  }
}