Mock a zip response using fetch-mock

Question

I've tried with following code:

require( 'isomorphic-fetch' );

const fetchMock = require( 'fetch-mock' ),
    fsp = require( 'fs-promise' ),
    unzip = require( 'unzip' ),
    rimraf = require( 'rimraf-then' ),
    path = require( 'path' );

let zipLink = 'https://github.com/stevemao/left-pad/archive/master.zip',
    out = 'left-pad-master';

// Careful: lib might be removed at any moment.
fetchMock.get( zipLink,
    fsp.createReadStream( path.join( __dirname, 'left-pad-master.zip' ) ) );

rimraf( out )
    .then( () => fetch( zipLink ) )
    .then( response => {
        return new Promise( ( resolve, reject ) => {
            // For example purpose, just parse zip file, and log each entry.
            response.body.pipe( unzip.Parse() )
                .on( 'entry', ( entry ) => console.log( entry.path ) )
                .on( 'close', resolve )
                .on( 'error', reject );
        } );
    } )
    .then( () => console.log( 'done' ) )
    .catch( console.log );

But it throws:

Error: invalid signature: 0x725f227b
    at C:\dev\unzip-mock\node_modules\unzip\lib\parse.js:59:13
    at runCallback (timers.js:628:20)
    at tryOnImmediate (timers.js:601:5)
    at processImmediate [as _immediateCallback] (timers.js:578:5)

If you comment out fetchMock.get call, and work with a real fetch it works well.

Code is available at https://github.com/mlewand/unzip-mock-example

Answer 1

Pass an instance of Response as a second parameter to fetchMock.get() where the body of response object is a stream of local file:

require( 'isomorphic-fetch' );

const fetchMock = require( 'fetch-mock' ),
    fsp = require( 'fs-promise' ),
    unzip = require( 'unzip' ),
    rimraf = require( 'rimraf-then' ),
    path = require( 'path' );

let zipLink = 'https://github.com/stevemao/left-pad/archive/master.zip',
    out = 'left-pad-master';

// Careful: lib might be removed at any moment.
var resp = new Response(
    fsp.createReadStream( path.join( __dirname, 'left-pad-master.zip' ) ),
    { headers: { "Content-Type" : "application/zip" } }
);
fetchMock.get(zipLink, resp);

rimraf( out )
    .then( () => fetch( zipLink ) )
    .then( response => {
        return new Promise( ( resolve, reject ) => {
            // For example purpose, just parse zip file, and log each entry.
            response.body.pipe( unzip.Parse() )
                .on( 'entry', ( entry ) => console.log( entry.path ) )
                .on( 'close', resolve )
                .on( 'error', reject );
        } );
    } )
    .then( () => console.log( 'done' ) )
    .catch( console.log );