Split out server and app

We experienced a lot of issues replacing mocha because server.js
had a lot of complicated code and it wasn’t clear what was happening.
This commit starts to address this issue by splitting the server and
the app logic into separate files (server.js and app.js)

As mentioned in this blog
http://www.albertgao.xyz/2017/05/24/how-to-test-expressjs-with-jest-and-supertest/.
There is no need to add listeners to the app for testing and seems to
be a best practice.

__tests__/spec/sanity-checks.js

@@ -1,6 +1,6 @@
 /* eslint-env jest */
 var request = require('supertest')
-var app = require('../../server.js')
+var app = require('../../app.js')
 var path = require('path')
 var fs = require('fs')
 var assert = require('assert')

app.js

@@ -3,7 +3,6 @@ const path = require('path')
 
 // NPM dependencies
 const bodyParser = require('body-parser')
-const browserSync = require('browser-sync')
 const dotenv = require('dotenv')
 const express = require('express')
 const nunjucks = require('nunjucks')
@@ -58,13 +57,11 @@ var useAuth = process.env.USE_AUTH || config.useAuth
 var useAutoStoreData = process.env.USE_AUTO_STORE_DATA || config.useAutoStoreData
 var useCookieSessionStore = process.env.USE_COOKIE_SESSION_STORE || config.useCookieSessionStore
 var useHttps = process.env.USE_HTTPS || config.useHttps
-var useBrowserSync = config.useBrowserSync
 var gtmId = process.env.GOOGLE_TAG_MANAGER_TRACKING_ID
 
 env = env.toLowerCase()
 useAuth = useAuth.toLowerCase()
 useHttps = useHttps.toLowerCase()
-useBrowserSync = useBrowserSync.toLowerCase()
 
 var useDocumentation = (config.useDocumentation === 'true')
 
@@ -349,25 +346,4 @@ app.use(function (err, req, res, next) {
 console.log('\nGOV.UK Prototype Kit v' + releaseVersion)
 console.log('\nNOTICE: the kit is for building prototypes, do not use it for production services.')
 
-// Find a free port and start the server
-utils.findAvailablePort(app, function (port) {
-  console.log('Listening on port ' + port + '   url: http://localhost:' + port)
-  if (env === 'production' || useBrowserSync === 'false') {
-    app.listen(port)
-  } else {
-    app.listen(port - 50, function () {
-      browserSync({
-        proxy: 'localhost:' + (port - 50),
-        port: port,
-        ui: false,
-        files: ['public/**/*.*', 'app/views/**/*.*'],
-        ghostmode: false,
-        open: false,
-        notify: false,
-        logLevel: 'error'
-      })
-    })
-  }
-})
-
 module.exports = app

server.js

@@ -0,0 +1,34 @@
+// NPM dependencies
+const browserSync = require('browser-sync')
+
+// Local dependencies
+const app = require('./app.js')
+const config = require('./app/config.js')
+const utils = require('./lib/utils.js')
+
+// Set up configuration variables
+var useBrowserSync = config.useBrowserSync.toLowerCase()
+var env = (process.env.NODE_ENV || 'development').toLowerCase()
+
+// Find a free port and start the server
+utils.findAvailablePort(app, function (port) {
+  console.log('Listening on port ' + port + '   url: http://localhost:' + port)
+  if (env === 'production' || useBrowserSync === 'false') {
+    app.listen(port)
+  } else {
+    app.listen(port - 50, function () {
+      browserSync({
+        proxy: 'localhost:' + (port - 50),
+        port: port,
+        ui: false,
+        files: ['public/**/*.*', 'app/views/**/*.*'],
+        ghostmode: false,
+        open: false,
+        notify: false,
+        logLevel: 'error'
+      })
+    })
+  }
+})
+
+module.exports = app