Not able to post data while using Supertest with mock-fs and Jest

Question

I am trying to send the POST request to my '/convert' route but I am getting body as an empty object in that route. I am using Supertest and mock-fs(to mock my file system). If I remove the mock({...}) method from my test file and try to send the same POST request then it is working perfectly fine. I am getting the req.body value in the '/convert' route while not using mock({...}) method. I want the mock-fs to work while sending the POST request using Supertest and the body should be available in the '/convert' route.

Please help or suggest me what I am doing wrong as I have already searched a lot but couldn't get any useful information on this scenario.

// testing.spec.ts

import request from 'supertest';
import mock from 'mock-fs';

describe('Converts HTML to PDF', () => {
    beforeEach(() => {

            const mockStorage = {
                mode: 0o777,
                items: {
                    '654321': mock.directory({mode: 0o775})
                }
            }

            const mockAppDirectory = {
                mode: 0o777,
                items: {
                    'storage': mock.directory(mockStorage)
                }
            }

            mock({
                '/app': mock.directory(mockAppDirectory)
            })

    });
    afterEach(function() {
        mock.restore();
    });

    test('test', async (done) => {
        const testData = {
          header:"test",
           footer:"test",
           body:"test",
           dpi:200,
           filename:"test",
        };
        const res = await request(app)
                    .post('/convert')
                    .send(testData)
                    .expect(200)
                    
        done();
    });
})

// testRoute.ts

import express from "express";
const router = express.Router();

router.post('/convert', async (req: Request, res: Response) => {
    console.log(JSON.stringify(req.body));
);

export default router;

Answer 1

Here is the solution after spending days. In order to fetch the body from the request we need body-parser and body-parser is present in the node_modules directory. By default, all files are lazy loaded in mock-fs so mock-fs only mocks and loads those directories which we specify using the mock function. In my code, I am not explicitly loading the node_modules directory and hence mock-fs is not aware of the body-parser module. So, I tried loading the node_modules explicitly and worked like a charm.

mock({
     // @ts-ignore
     'node_modules': mock.load(path.resolve('node_modules')),
     '/app': mock.directory({ mode: 0o775 })
});