Using Q library for HTTP api response testing in nodejs - node.js

Question

how to use Q to make it wait until previous response has come from the server.
What I am looking to do here is compare the response from test server and production server for the same request.
I get the responses back from both the servers, but unable to compare them since the assert statement is executed before the response comes back.
Any one know what I am doing wrong. heres the code.
var Q = require('q');
var path='';
var prodResponse = '';
var tstReponse = '';
Q.fcall(readFile())
.then(secondFunction())
.then(thirdFunction())
.then(function(){
console.log("prodResponse: "+prodResponse);
console.log("tstResponse: "+tstResponse);
assert.strictEqual(prodResponse, tstResponse)
})
.catch(function(){
console.log('error occurred');
})
.done();
function readFile(){
fs.readFile('hostname.json', function (err, data) {
if (err) return console.error(err);
path = JSON.parse(data);
return JSON.parse(data);
});
}
function secondFunction(){
var prodOptions = {
hostname: 'somehostname.com',
port: 80,
path: "/path?"+path.path,
method: 'POST',
headers: {
'Content-Type': 'application/json;charset=UTF-8'
},
auth : ''
};
return http.request(prodOptions, function(res) {
console.log('Prod');
res.setEncoding('utf8');
res.on('data', function (chunk) {
prodResponse = chunk;
return chunk;
});
res.on('end', function() {
console.log('No more data in response.');
})
}).on('error', function(e) {
console.log('problem with request: ' + e.message);
}).end();
}
function thirdFunction(){
// same a second, only difference is the response http.
}

Answer 1

There is multiple errors in your code
Q.fcall(readFile())
Your q variable is q and not Q. So this line will crash because Q is undefined (javascript is case sensitive).
Then, readFile doesn't return any promise (in fact, it returns nothing). So the q library can't use anything to wait the end of any asynchronous work. The then callbacks will be fired immediatly.

Answer 2

You can use Q.ninvoke to make your readFile function return a promise, and you can use Q.defer to create and return a promise from your secondFunction:
var Q = require('q');
var path='';
var prodResponse = [];
var tstReponse = '';
readFile()
.then(secondFunction())
.then(thirdFunction())
.then(function(){
console.log("prodResponse: "+prodResponse);
console.log("tstResponse: "+tstResponse);
assert.strictEqual(prodResponse, tstResponse)
})
.catch(function(){
console.log('error occurred');
})
.done();
function readFile(){
return Q.ninvoke(fs, 'readFile', 'hostname.json').then(function (data) {
path = JSON.parse(data);
return path;
}, function (err) {
console.error(err);
});
}
function secondFunction(){
var prodOptions = {
hostname: 'somehostname.com',
port: 80,
path: "/path?"+path.path,
method: 'POST',
headers: {
'Content-Type': 'application/json;charset=UTF-8'
},
auth : ''
};
var defer = Q.defer();
var chunks = [];
http.request(prodOptions, function(res) {
console.log('Prod');
res.setEncoding('utf8');
res.on('data', function (chunk) {
chunks.push(chunk);
});
res.on('end', function() {
console.log('No more data in response.');
prodResponse = chunks.join('');
defer.resolve(prodResponse);
})
}).on('error', function(e) {
console.log('problem with request: ' + e.message);
defer.reject(e);
}).end();
return defer.promise;
}
function thirdFunction(){
// same a second, only difference is the response http.
}