Read response output buffer/stream with supertest/superagent on node.js server

Question

I am trying to write a test that checks whether an API route outputs a ZIP file with the correct contents.

I am using mocha and supertest for testing, and I would like to actually read the output stream/buffer, read the zip file contents and see if the contents are correct.

Any ideas how should I do it? When I try to read res.body, it's just an empty object.

  request(app)
    .get( "/api/v1/orders/download?id[]=1&id=2" )
    .set( "Authorization", authData )
    .expect( 200 )
    .expect( 'Content-Type', /application\/zip/ )
    .end( function (err, res) {
      if (err) return done( err );

      console.log( 'body:', res.body )

      // Write the temp HTML file to filesystem using utf-8 encoding
      var zip = new AdmZip( res.body );
      var zipEntries = zip.getEntries();

      console.log( 'zipentries:', zipEntries );

      zipEntries.forEach(function(zipEntry) {
        console.log(zipEntry.toString()); // outputs zip entries information
      });

      done();
    });

Answer 1

Expanding on @Beau's answer, the following can be used to get any binary response content as a Buffer which you can examine further in request.end():

function binaryParser(res, callback) {
    res.setEncoding('binary');
    res.data = '';
    res.on('data', function (chunk) {
        res.data += chunk;
    });
    res.on('end', function () {
        callback(null, new Buffer(res.data, 'binary'));
    });
}

// example mocha test
it('my test', function(done) {
    request(app)
        .get('/path/to/image.png')
        .expect(200)
        .expect('Content-Type', 'image.png')
        .buffer()
        .parse(binaryParser)
        .end(function(err, res) {
            if (err) return done(err);

            // binary response data is in res.body as a buffer
            assert.ok(Buffer.isBuffer(res.body));
            console.log("res=", res.body);

            done();
        });
});

Answer 2

I think you'll want to create your own parser for application/zip and use that to get at the actual response data; the JSON parser is here, for example. Once you've got that you can use it by passing it to request.parse; so your test would become:

request(app)
  .get( "/api/v1/orders/download?id[]=1&id=2" )
  .set( "Authorization", authData )
  .expect( 200 )
  .expect( 'Content-Type', /application\/zip/ )
  .parse( function (res, fn) {
    res.data = '';
    res.on( 'data', function (chunk) { res.data += chunk; } );
    res.on( 'end', function () {
      try {
        fn( null, new AdmZip( res.data ) );
      } catch ( err ) {
        fn( err );
      }
    });
  })
  .end( function (err, res) {
    if (err) return done( err );

    console.log( 'body:', res.body )

    // Write the temp HTML file to filesystem using utf-8 encoding
    var zipEntries = res.body.getEntries();

    console.log( 'zipentries:', zipEntries );

    zipEntries.forEach(function(zipEntry) {
      console.log(zipEntry.toString()); // outputs zip entries information
    });

    done();
  });

To find the answer to this I mostly relied on inspecting the superagent test suite. :)

Answer 3

Existing answers didn't work for me. What I ended up doing was:

// parses response.body buffer into a data object
const parsePDF = response => {
  return new Promise((resolve, reject) => {
    // code that parses response.body as buffer
    // and calls resolve(data); when done
    // or reject(err); on error
  })
};

const binaryParser = require('superagent-binary-parser');

// test snippet
request(app)
    .get('/some/api/returning/pdf')
    .expect(200)
    .expect('content-type', 'application/pdf')
    .parse(binaryParser)
    .buffer()
    .then(parsePDF)
    .then((pdf) => {
      chai.expect(pdf.pages.length).to.be.equal(5);
    })