使用Jest对multer Node.js的代码覆盖率进行单元测试

Question

我试图涵盖Node.js中简单的multer文件的代码覆盖率的行和函数，但我没有搞错。

以下是文件：

fileUpload.js

​

const express = require("express");
const multer = require("multer");
const path = require("path");

const storage = multer.diskStorage({
  destination: (req, file, callBack) => {
    callBack(null, "uploads");
  },
  filename: (req, file, callBack) => {
    callBack(null, `${file.originalname}`);
  },
});

const upload = multer({
  storage: storage,
  fileFilter: (req, file, cb) => {
    if (file.mimetype == "image/png" || file.mimetype == "image/jpg" || file.mimetype == "text/plain") {
      cb(null, true);
    } else {
      cb(null, false);
      return cb(new Error('Only .png, .jpg, .txt and .jpeg format allowed!'));
    }
  }
})
module.exports = {
  upload,
  express
};

​

fileUpload.test.js

const multer = require('multer')
const fileStorage = require("../file-storage");

jest.mock('multer', () => {
  const multer = () => ({
    diskStorage: () => {
      return {
        destination: (req, res, callBack) => {
          callBack(null, 'uploads')
        },
        filename: (req, res, callBack) => {
          req.body = {
            userName: 'testUser'
          }
          req.files = [{
            originalname: 'sample.name',
            mimetype: 'sample.type',
            path: 'sample.url',
            buffer: Buffer.from('whatever'), // this is required since `formData` needs access to the buffer
          }, ]
          return callBack()
        }
      }

    },
  })
  multer.diskStorage = () => jest.fn()
  return multer

})

describe('65317652', () => {
  const upload = fileStorage.upload
  it('should pass', () => {
    const storage = upload.diskStorage();
    const uploadData = multer({
      storage: storage
    });
    expect(uploadData).toBeTruthy();
  });
});

我搜索了很多博客，但没有找到合适的解决方案。

​

​

如何覆盖这些线路？

Answer 1

这可能不是测试使用multer的模块的最佳方法(我个人不知道这个库)。但是，您可以通过以下方式设法到达您的代码。

1. 去掉了你的模拟，因为你想要覆盖你的文件中的代码-存储. in，而不是你模拟的代码.
2. 执行所有的调用来到达你想要覆盖的代码.

以下是如何从文件-storage.js中到达“目的地”代码：

const multer = require('multer')
const fileStorage = require("../file-storage");

// 1 - Get rid of mock since this is not what you want to cover
//
// jest.mock('multer', () => {
//     const multer = () => ({
//         diskStorage: () => {
//             return {
//                 destination: (req, res, callBack) => {
//                     callBack(null, 'uploads')
//                 },
//                 filename: (req, res, callBack) => {
//                     req.body = {
//                         userName: 'testUser'
//                     }
//                     req.files = [{
//                         originalname: 'sample.name',
//                         mimetype: 'sample.type',
//                         path: 'sample.url',
//                         buffer: Buffer.from('whatever'), // this is required since `formData` needs access to the buffer
//                     },]
//                     return callBack()
//                 }
//             }

//         },
//     })
//     multer.diskStorage = () => jest.fn()
//     return multer

// })

describe('65317652', () => {
    const upload = fileStorage.upload
    it('should pass', () => {
        const storage = upload;
        const multerRes = multer({
            storage: storage
        });
        
        // 2 - Perform all calls in order to reach the code you want to cover.
        //
        expect(multerRes).toBeTruthy();
        const diskStorageRes = multerRes.storage.storage
        expect(diskStorageRes).toBeTruthy();
        const getDestinationRes = diskStorageRes.getDestination()
        expect(getDestinationRes).toBeTruthy();

    });

});

似乎还有其他更合适的方法来测试穆特。例如，请参见https://stackoverflow.com/a/58474936/6210975。