Force HTTP error in node.js requests

force-http-error.js

var http = require('http');
var request = require('request');

function forceHttpError(error) {
    var originalHttpRequest = http.request;
    // Monkey-patch the http.request method with
    // our implementation
    http.request = function (opts, cb) {
        // Call the original implementation of http.request()
        var req = originalHttpRequest(opts, cb);

        // In next tick, simulate an error in the http module
        process.nextTick(function () {
            req.emit('error', error);
            // Prevent Request from waiting for
            // this request to finish
            req.removeAllListeners('response');
            // Properly close the current request
            req.end();
        })

      // We must return this value to keep it
      // consistent with original implementation
      return req;
    };

    return originalHttpRequest;
}

function unforceHttpError(originalHttpRequest) {
    http.request = originalHttpRequest;
}

function getUrl(url, cb) {
    request(url, function (err, response, body) {
        if (err) {
            console.error('Error in GET %s: %s', url, err);
        } else {
            console.log('Successful GET %s...', body.toString().slice(0, 100));
        }
        return cb(err, body);
    });
}


var o1 = forceHttpError(new Error('Forced error'));

getUrl('http://google.com', function(err, body) {
    unforceHttpError(o1);

    getUrl('http://google.com', function(err, body) {
        var o2 = forceHttpError(new Error('Other forced error'));

        getUrl('http://google.com', function(err, body) {
            unforceHttpError(o2);
        });
    });
});