JavaScript Test should pass on stream error, fail on success

I'm trying to write a mocha test which passes on a stream error but fails if the stream ends without an error.

Detecting the error is no problem, but the finish handler is always called, even if the stream is forced to error out. In this code, the error handler's should.exist(err) assertion works correctly, but then the finish handler still throws an error.

describe('catch stream errors', function() {
  it('should throw an error', function(done) {
    var stream = failStream();

    stream.on('error', function(err) {
      should.exist(err);
      done();
    })

    stream.on('finish', function() {
      done(new Error('Why does this still run?'));
    });

    stream.write();
    stream.end();
  })
})

One workaround, which seems like a bit of a hack, is to scope an errored variable above the handlers, then flip it in the error handler and check the value in the finish handler. Seems like there should be a better way of handling this.

var errored = false;

stream.on('error', function(err) {
  should.exist(err);
  errored = true;
  done();
})

stream.on('finish', function() {
  if (!errored) {
    done(new Error('Error suppressed'));
  }
});

Full gist here.

Answer:1

A more elegant solution is to remove the finish listener from inside the error listener. This is similar to the cleanup method in node's lib/stream source file.

// Refactor out the listeners
var onerror = function(err) {
  should.exist(err);
  this.removeListener('finish', onfinish);
  done();
};

var onfinish = function() {
  done(new Error('Expected stream to throw an error.'));
};

stream.on('error', onerror);
stream.on('finish', onfinish);

Answer:2

Change value in react js on window resize

I'm building a photo gallery in react js. Obviously it's going to have to be responsive and I've tackled this by setting values like so in the component's render method: let thumbWidth = window....

change value react
change value react-select
change props value react
change context value react
change input value react
change state value react
change props value react native
change textinput value react native
change ref value react
change state value react native
change animated value react native
change text value react native
change checkbox value react
change value onclick react
change const value react
change array value react
change textarea value react
change context value react hooks
change const value react native
change input value react testing library

ajax GET Not working (Service Data not getting)

We have URL when we hit URL URL in browser we got data. We got Data like [{"UserId":"c2fbd9fb-a423-4d33-9ea4-3aa58f7b52cf","UserType":"Parent","OutPutMessage":"Sucess"}]. But We need get data ...

How to unblock the Developer tools

I want to access the developer tools on this domain "http://umang.gov.in" using F12 or right click of the mouse but the site website developer block this option. I follow this step to access this. ...

how to unblock developer tools on chromebook

Loading template not showing in Ember app

I am developing an Ember-cli app with ember 2.1. I created a templates/loading.hbs and several other templates. My foo template has a input that I use to send a queryParam to foo/bar. foo/bar uses the ...