Mock child process

[johnsonsamuel]

What is this about?

Mock node's child process exec or spawn ?

Just wanted to check if there is a possibility of mocking node process.

__installPackage.js__

const {promisify} = require('util');
const exec = (require('child_process').exec);

const listFolderContent = async (root) => {
    const options = {
        cwd: root
    };

    await exec('ls -l', options, (err, data) => {
        if(err) console.log('error', err);
    });
};

_installPackage.test.js_

const mock = require('mock-fs');
const {listFolderContent} = require('./listFolderContent');

describe('listFolderContent', async assert => {
    const root = 'my-app';

    mock({
        'my-app': {
            'test.txt': 'samuel'
        }

    });

   await listFolderContent(root);    

   mock.restore();
});

My question is, will the exec work and list the content from the mock fs?

which is test.txt?

[3cp]

The answer is no. Mockfs cannot do it. First, exec or spawn creates new OS process which is isolated from current nodejs process. Even if you do exec("node some.js") to create another nodejs process, the new process is not affected by mockfs on current process.

Furthermore, ls uses libc to access file system, it's irrelevant to mockfs which only mocks nodejs's fs module.

[johnsonsamuel]

Thank you @3cp for your detailed explanation. I was able to mock exec using sinon. I was able to use mock-fs as well.