开玩笑地模拟 fs 与配置模块发生冲突

Question

我正在尝试对以下文件进行单元测试：

import { readFileSync } from 'fs';
import logger from './logger.utils';

export const readFile = async (targetDir: string, fileName: string): Promise<string> => {
  logger.info(`start reading from ${targetDir}/${fileName}`);
  const data = readFileSync(`${targetDir}/${fileName}`, {encoding: 'utf8', flag: 'r'});

  return data;
};

jest测试文件

import { mocked } from 'ts-jest/utils';
import fs from 'fs';
jest.mock('fs');
import * as fsUtils from '../../src/utils/fs.utils';

let readFileSyncMock: jest.SpyInstance;

describe('fs.utils', () => {
  describe('readFile', () => {
    afterEach(() => {
      readFileSyncMock.mockReset();
    });
    afterAll(() => {
      readFileSyncMock.mockRestore();
    });
    it('should create a new log directory if one doesn\'t already exist', async () => {
      mocked(fs.readFileSync as jest.Mock).mockImplementation(() => { ('some string') });
    
      const fileData = await fsUtils.readFile('target_directory', 'file_name');
    
      expect(fileData).toEqual('some string');
    });
  });
});

当我运行测试时出现以下错误：

Config file /Users/dfaizulaev/Documents/projectname/config/runtime.json cannot be read. Error code is: undefined. Error message is: Cannot read property 'replace' of undefined

  1 | import loggingContext from './loggingContext';
> 2 | import config from 'config';
    | ^
  3 | import os from 'os';
  4 | import constants from '../../config/constants';
  5 |

  at Config.Object.<anonymous>.util.parseFile (node_modules/config/lib/config.js:821:13)
  at Config.Object.<anonymous>.util.loadFileConfigs (node_modules/config/lib/config.js:697:26)
  at new Config (node_modules/config/lib/config.js:116:27)
  at Object.<anonymous> (node_modules/config/lib/config.js:1492:31)
  at Object.<anonymous> (src/utils/logger.utils.ts:3:1)

错误来自于上述fs模块文件导入的logger文件。

logger.utils 文件

import loggingContext from './loggingContext';
import config from 'config';
import os from 'os';
import constants from '../../config/constants';

const LOG_LEVEL: string = config.get(constants.LOG_LEVEL);

.... more logic ....

我认为错误的原因是我没有正确模拟 fs 模块，但我尝试了各种方法并不断收到此错误。

请指教

Answer 1

问题是因为我正在模拟 config 包中使用的整个 fs 模块。

删除了 jest.mock('fs'); 并分别模拟了这些方法。

例如：

import fs, { Stats, promises } from 'fs';
import * as fsUtils from '../../src/utils/fs.utils';

describe('fs.utils', () => {
  afterEach(() => {
    jest.resetAllMocks();
  });
  describe('statSync', () => {
    it('Should successfully call statSync', () => {
      jest.spyOn(fs, 'statSync').mockReturnValue({ size: 1000 } as Stats);
      const result = fsUtils.getFileSize('file path');
      expect(result).toEqual(1000);
    });
  });
  describe('writeFile', () => {
    it('Should successfully call writeFile', async () => {
      jest.spyOn(promises, 'writeFile').mockResolvedValue();
      await fsUtils.writeFile('file path', 'data');
    });
  });
  describe('writeFile', () => {
    it('Should successfully call writeFile', async () => {
      jest.spyOn(promises, 'readFile').mockResolvedValue('some file content');
      const result = await fsUtils.readFile('filePath', 'fileName');
      expect(result).toEqual('some file content');
    });
  });
});

开玩笑地模拟 fs 与配置模块发生冲突

Mocking fs with jest clashes with config module

fs

typescript

jestjs

ts-jest