How do you test a expressApp.post()? - node.js

Question

I a C# developer trying to learn node.js / Dialogflow on the fly. I am trying to create a webhook in node.js on Azure that I would use as a fulfillment for my Dialogflow project.
My understanding is that I need to convert the following
exports.dialogflowFirebaseFulfillment = functions.https.onRequest(app);
to
expressApp.post( '/dialogflowFulfillment', (request, response) => {
}
'use strict';
var debug = require('debug');
var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var routes = require('./routes/index');
var users = require('./routes/users');
var app = express();
// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'pug');
// uncomment after placing your favicon in /public
//app.use(favicon(__dirname + '/public/favicon.ico'));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));
app.use('/', routes);
app.use('/users', users);
// catch 404 and forward to error handler
app.use(function (req, res, next) {
var err = new Error('Not Found');
err.status = 404;
next(err);
});
// error handlers
// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
app.use(function (err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: err
});
});
}
// production error handler
// no stacktraces leaked to user
app.use(function (err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: {}
});
});
app.post('/dialogflowFulfillment', function (req, res) {
res.send('POST request to homepage');
});
app.set('port', process.env.PORT || 3000);
var server = app.listen(app.get('port'), function () {
debug('Express server listening on port ' + server.address().port);
});
My question is how do I test the 'expressApp.post()' so I know its getting called. I used Visual Studio 2017 and created a blank node.js express app then I added the post function. I run app and then use the Postman app to send a post request to the url (localhost:3000)/dialogflowFulfillment but I get a 404 error.
What am I missing? Thank you for your help!

Answer 1

You have to move your function above the error handling:
app.use('/', routes);
app.use('/users', users);
// Put your function right here
app.post('/dialogflowFulfillment', function (req, res) {
res.send('POST request to homepage');
});
// Catch 404 and forward to error handler
app.use(function (req, res, next) {
var err = new Error('Not Found');
err.status = 404;
next(err);
});
The function to catch 404 and forward to error handling does the following as described here:
Calls to next() and next(err) indicate that the current handler is
complete and in what state. next(err) will skip all remaining
handlers in the chain except for those that are set up to handle
errors as described above.

Answer 2

Express sends 404 HTTP error because the sequence of adding middlewares does matter.
As far as you added 404 error sending middleware right after app.use('/users', users); middleware, 404 middleware will be executed next - it will throw send an error ( next(err); ) to next middleware which catches all errors and sends response. To resolve this issue you need to .use error handling middlewares right after all other middlewares:
app.post('/dialogflowFulfillment', function (req, res) {
res.send('POST request to homepage');
});
// catch 404 and forward to error handler
app.use(function (req, res, next) {
var err = new Error('Not Found');
err.status = 404;
next(err);
});
// production error handler
// no stacktraces leaked to user
app.use(function (err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: {}
});
});