Test Express behavior wrt next() / next('route') / ..

test.js

var express = require('express')
var app = express()

var handler = function (req,res,next,where,what) {
  console.log('  ' + where + ' === ' + what)
  switch(what) {

    case 'stop':
      console.log('  ' + where + ':stop -> (do nothing)')
      break

    case 'next':
      console.log('  ' + where + ':next -> next()')
      next()
      break

    case 'text':
      console.log('  ' + where + ":text -> next('" + where + ":text')")
      next('' + where + ':text')
      break

    case 'error':
      console.log('  ' + where + ":error -> next(new Error('" + where + ":error'))")
      next(new Error('' + where + ':error'))
      break

    case 'route':
      console.log('  ' + where + ":route -> next('route')")
      next('route')
      break

    case 'send':
      console.log('  ' + where + "send -> res.send('" + where + "-send')")
      res.send('' + where + '-send')
      break

    case 'send-and-next':
      console.log('  ' + where + "send-and-next -> res.send('" + where + "-send-and-next'); next()")
      res.send('' + where + '-send-and-next')
      next()
      break

    case 'auth':
      switch( req.query.user ) {
        case 'next':
          console.log('  ' + where + ":auth(next) -> next()")
          next()
          break
        case 'route':
          console.log('  ' + where + ":auth(route) -> next('route')")
          next('route')
          break
        default:
          next(new Error('' + where + ':auth(*), invalid user ' + req.query.user))
          break
      }
      break

    case 'auth-route':
      if(req.query.user === 'admin') {
        console.log('  ' + where + ":admin -> next('route')")
        next('route')
      } else {
        next(new Error('' + where + ': invalid user: ' + req.query.user))
      }
      break

    default:
      console.log('  ' + where + ":* -> res.send('" + where + "-default')")
      res.send('' + where + 'default')
      break
  }
}

app.use(function(req,res,next) {
  console.log('')
  next()
})

app.use(function(req,res,next) {
  console.log('USE')
  if( req.query.use ) {
    handler(req,res,next,'use',req.query.use)
  } else {
    next()
  }
})

app.use(function(req,res,next) {
  console.log('USE2')
  if( req.query.use2 ) {
    handler(req,res,next,'use2',req.query.use2)
  } else {
    next()
  }
})

app.get('/base/:head/:tail', function (req,res,next) {
  console.log('GET /:head/:tail -- head === ' + req.params.head)
  handler(req,res,next,'head',req.params.head)
}, function (req,res,next) {
  console.log('GET /:head/:tail -- tail === ' + req.params.tail)
  handler(req,res,next,'tail',req.params.tail)
})

app.get('/all/:head/:tail/*', function (req,res,next) {
  console.log('GET /:head/:tail -- head === ' + req.params.head)
  handler(req,res,next,'head',req.params.head)
}, function (req,res,next) {
  console.log('GET /:head/:tail -- tail === ' + req.params.tail)
  handler(req,res,next,'tail',req.params.tail)
})

app.get( /./, function(req,res,next) {
  console.log('GET ' + req.path + ' -> res.send("' + req.path + ' OK")')
  res.send('' + req.path + ' OK')
})

var server = app.listen(3000, function () {
  var host = server.address().address;
  var port = server.address().port;

  console.log('Example app listening at http://%s:%s', host, port);
})

Compare for example:

http://127.0.0.1:3000/base/route/send # send is skipped
http://127.0.0.1:3000/base/next/route # next('route') behaves same as next() in last callback
http://127.0.0.1:3000/base/next/route?use=route # next('route') behaves as res.send('route') in middleware

http://127.0.0.1:3000/base/auth/send/foo # No auth is performed
http://127.0.0.1:3000/all/auth/send/foo # Auth rejected
http://127.0.0.1:3000/all/auth/send/foo?user=bar # Auth rejected
http://127.0.0.1:3000/all/auth/send/foo?user=next # Auth accepted, res.send() executed, no next()
http://127.0.0.1:3000/all/auth/send-and-next/foo?user=next # Auth accepted, res.send() executed, complains about doing res.send() twice