在导出单元测试之前等待应用程序？

Question

I'm attempting to use Jest to unit test an express API I've been working on however the database has to be ready before it runs the test. This does not seem to be happening however. I have a server.ts file which contains:

import App from './app';
import UsersController from './controllers/users.controller';

const app = new App();

app.initialize(
  [
    new UsersController(),
  ]
);

if (process.env.NODE_ENV !== 'test') {
  app.listen();
}

export default app;

app.initialize is an aysnc function which configures the database and routes my controllers.

In my unit test I then have the following

import server from "../server";
import supertest from 'supertest';

const request = supertest(server.app);

it('should allow users to register', async () => {
    // Arrange
    const user = {
      firstName: 'John',
      lastName: 'Smith',
      age: 42
    };

    return request.post('/api/users')
      .send(user)
      .set('Accept', 'application/json')
      .then(response => {
        expect(response).toEqual(user.firstName)
        expect(response.body.lastName).toEqual(user.lastName)
        expect(response.body.id).toBeGreaterThan(0)
    });
});

This however falls over with a 404 error, however if I remove the NODE_ENV check on "test" in the server file I can see that app.listen() get's called well after my test so I believe it's safe to assume that the tests are running before that file has finished.

For completeness here is my App class:

import "reflect-metadata";
import express from 'express';
import * as bodyParser from 'body-parser';
import {createConnection} from "typeorm";
import IController from './controllers/baseController.interface';

class App {
  public app = express();
  public port: number = 8080;
  public ready: boolean = false;

  public async initialize(controllers : [IController]) {
    await createConnection().then(async connection => {
      connection.synchronize();
      this.initializeMiddlewares();
      this.initializeControllers(controllers);
    });
  }

  private initializeMiddlewares() {
    this.app.use(bodyParser.json());
  }

  private initializeControllers(controllers : [IController]) {
    controllers.forEach((controller) => {
      this.app.use('/api/', controller.router);
    });
  }

  public listen() {
    this.app.listen(this.port, () => {
      console.log(`App listening on the port ${this.port}`);      
    });
  }
}

export default App;

Answer 1

You can try wrapping your App instance creation code inside a function. You can then wait for it inside your tests. In your server.ts do the following:

import App from './app';
import UsersController from './controllers/users.controller';

const getApp = async () => {
   const app = new App();

  await app.initialize(
  [
   new UsersController(),
  ] 
  );

}

getApp().then( appInstance => {
if (process.env.NODE_ENV !== 'test') {
   appInstance.listen();
}})

export default getApp;

In your test file just call the function to get your app instance:

import getApp from "../server";
import supertest from 'supertest';


it('should allow users to register', async () => {
  const app = await getApp()
  const request = supertest(app);
  // Arrange
  const user = {
    firstName: 'John',
    lastName: 'Smith',
    age: 42
  };

 return request.post('/api/users')
   .send(user)
   .set('Accept', 'application/json')
   .then(response => {
     expect(response).toEqual(user.firstName)
     expect(response.body.lastName).toEqual(user.lastName)
     expect(response.body.id).toBeGreaterThan(0)
 });
});