Jest模拟FS文件流

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const csv = require('csv-parser');
let storeData=[];
csvFileReader() {
        fs.createReadStream(path.resolve(__dirname, "./abc.csv"))
            .pipe(csv())
            .on('data',  async (row) => {
                storeData[0] = row.postcode;
            .on('end', () => {              
                console.log('Done')
    }

import ReadFile from './readFile.js';
const fs = require('fs');
jest.mock('fs');
describe('Load File', () => {
    const readFile= new ReadFile();
    test('Test data handler', async () => {
        const mockPipeOn = { on: jest.fn().mockImplementation(function(this, event, handler) {
            if (event === 'data') {
              jest.fn.mockReturnValueOnce("Reading Data")
            if (event === 'end') {
              jest.fn.mockReturnValueOnce("Completed Reading Data")
            return this;
          }), };
        const mockReadStream = { pipe: jest.fn().mockReturnValueOnce(mockPipeOn) };
        const createReadStream = jest.fn().mockReturnValueOnce(mockReadStream);
        await readFile.csvFileReader();
});

import fs from 'fs';
import path from 'path';
import csv from 'csv-parser';
class ReadFile {
  csvFileReader() {
    fs.createReadStream(path.resolve(__dirname, './abc.csv'))
      .pipe(csv())
      .on('data', async (row) => {
        console.log('Storing Data');
      .on('end', () => {
        console.log('Done');
export default ReadFile;

import ReadFile from './ReadFile';
import fs from 'fs';
jest.mock('fs');
describe('67216891', () => {
  const readFile = new ReadFile();
  it('should store', () => {
    const mReadStream = {
      pipe: jest.fn().mockReturnThis(),
      on: jest.fn().mockImplementation(function (event, handler) {
        handler();
        return this;
    fs.createReadStream.mockReturnValueOnce(mReadStream);
    readFile.csvFileReader();
    expect(fs.createReadStream).toBeCalledTimes(1);
    expect(mReadStream.pipe).toBeCalledTimes(1);
    expect(mReadStream.on).toBeCalledWith('data', expect.any(Function));
    expect(mReadStream.on).toBeCalledWith('end', expect.any(Function));
});

 PASS  examples/67216891/ReadFile.test.js (8.891 s)
  67216891
    ✓ should store (20 ms)
  console.log
    Storing Data
      at ReadFile.<anonymous> (examples/67216891/ReadFile.js:10:17)
  console.log
      at examples/67216891/ReadFile.js:13:17
-------------|---------|----------|---------|---------|-------------------
File         | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
-------------|---------|----------|---------|---------|-------------------
All files    |     100 |      100 |     100 |     100 |

Jest模拟FS文件流

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