每個單獨測驗的Jest模擬第三方默認匯出

我正在嘗試express使用jest和測驗控制器supertest。我有一個處理檔案處理的中間件multer。我可以multer在全球范圍內模擬，但我一直無法在每個it/test案例中模擬它。

// saveImage.controller.ts
jest.mock('multer', () => {
  const m = () => ({
    single: () => (req: Request, res: Response, next: NextFunction) => {
      req.body = { type: 'screenshots' };
      req.file = mockFile;
      return next();
    },
  });
  m.memoryStorage = () => jest.fn();
  return m;
});

describe('POST /api/v1/garment/image/upload', () => {
  it('should return 201', async () => {
    await request(app)
      .post('/api/v1/garment/image/upload')
      .send({ file: 'myImage' }) // this is overwritten by the mock 
      .expect(201); // passes
  });

  it('should return 400', async () => {
    await request(app)
      .post('/api/v1/garment/image/upload')
      .send() // this is overwritten by the mock
      .expect(400); // fails
  });
});

第一個測驗通過，但我無法更改模擬以通過第二個測驗。如何在我的第二種it情況下更改模擬？

uj5u.com熱心網友回復：

我將使用jest.doMock(moduleName, factory, options)來模擬multer。注意這個multer.single()方法會在模塊匯入的時候執行，所以我們在模塊匯入之前mock一下。

為了在模塊匯入時清除快取（可以快取模塊作用域變數、函式的函式等），需要jest.resetModules()在運行每個測驗用例之前使用。

app.ts：

import express from 'express';
import multer from 'multer';
import path from 'path';

const upload = multer({ dest: path.join(__dirname, 'uploads/') });
const app = express();

app.post('/api/v1/garment/image/upload', upload.single('file'), (req, res) => {
  console.log(req.file, req.body);
  if (req.file) {
    res.sendStatus(201);
  } else {
    res.sendStatus(400);
  }
});

export { app };

app.test.ts：

import request from 'supertest';
import multer from 'multer';
import { NextFunction, Request, Response } from 'express';

describe('69997349', () => {
  let app: typeof import('./app').app;
  beforeEach(async () => {
    jest.resetModules();
  });
  it('should return 201', async () => {
    const mockFile = { fieldname: 'myImage' } as Express.Multer.File;
    jest.doMock('multer', () => {
      const m = () => ({
        single: () => (req: Request, res: Response, next: NextFunction) => {
          req.body = { type: 'screenshots' };
          req.file = mockFile;
          return next();
        },
      });
      return m;
    });
    app = (await import('./app')).app;
    await request(app).post('/api/v1/garment/image/upload').send({ file: 'myImage' }).expect(201);
  });

  it('should return 400', async () => {
    jest.doMock('multer', () => {
      const m = () => ({
        single: () => (req: Request, res: Response, next: NextFunction) => {
          return next();
        },
      });
      return m;
    });
    app = (await import('./app')).app;
    await request(app).post('/api/v1/garment/image/upload').expect(400);
  });
});

測驗結果：

 PASS  examples/69997349/app.test.ts (8.245 s)
  69997349
    ? should return 201 (297 ms)
    ? should return 400 (23 ms)

  console.log
    { fieldname: 'myImage' } { type: 'screenshots' }

      at examples/69997349/app.ts:10:11

  console.log
    undefined undefined

      at examples/69997349/app.ts:10:11

Test Suites: 1 passed, 1 total
Tests:       2 passed, 2 total
Snapshots:   0 total
Time:        9.428 s, estimated 10 s

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