在开玩笑中模拟一个yaml文件

Question

I have a yaml file, that has some config information and I use it in a module that I want to test. But when I test it I want to mock it so it only has simplified and static data, so it's easy to test and if the config is changed I don't have to edit the tests. Here is what I tried so far:

// config/index.js

const yaml = require('js-yaml');
const fs = require('fs');
const path = require('path');

const filePath = path.join(__dirname, 'stuff.yaml');

module.exports =
{
    getStuff()
    {
        return yaml.safeLoad(fs.readFileSync(filePath, 'utf8'));
    },
    setStuff(stuff)
    {
        fs.writeFile(filePath, yaml.safeDump(stuff), err => console.log);
    }
}

// test/config.test.js

const config = require("../config")

test('getStuff', () => {
    jest.mock('../config/stuff.yaml')
    expect(config.getStuff()).toEqual({/*..*/});
});

My file structure being:

project-root/
├── config/
│   ├── __mocks__/
|       └── stuff.yaml     (the mock file)
│   ├── stuff.yaml     (the real file)
│   └── index.js
└── test/
    └── config.test.js

But the test still return the data from the real file. Summarizing, I want to mock a text file in the file system, so that any module reads it instead of the real one.

Note: I don't really care if the mock version is on the disk or I just have it as a string in memory. Having it in memory would even be beneficial in the sense of the tests being faster.

Answer 1

You can probably update your Jest configuration and leverage moduleNameMapper to handle this.

{
  "moduleNameMapper": {
    "config/stuff.yaml": "<rootDir>/config/__mocks__/stuff.yaml"
  }
}

Answer 2

你也可以试试setMock - https://facebook.github.io/jest/docs/en/jest-object.html#jestsetmockmodulename-moduleexports

jest.setMock('config/__mocks__/stuff.yaml', require('config/stuff.yaml');