Move listener to listen-on-port.js

This listener which looks out for file changes using BrowserSync doesn't need
to be part of `server.js` as it's only needed for npm start. We added a new file called
`listen-on-port.js` - this needs to be separate from `server.js` for Jest to work
correctly.

More detail here:
http://www.albertgao.xyz/2017/05/24/how-to-test-expressjs-with-jest-and-supertest/#2-Separate-your-app-and-sever

gulp/nodemon.js

@@ -30,7 +30,7 @@ const onQuit = () => {
 gulp.task('server', function () {
   nodemon({
     watch: ['.env', '**/*.js', '**/*.json'],
-    script: 'server.js',
+    script: 'listen-on-port.js',
     ignore: [
       config.paths.public + '*',
       config.paths.assets + '*',

listen-on-port.js

@@ -0,0 +1,32 @@
+
+// NPM dependencies
+const browserSync = require('browser-sync')
+
+// Local dependencies
+const server = require('./server.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()
+
+utils.findAvailablePort(server, function (port) {
+  console.log('Listening on port ' + port + '   url: http://localhost:' + port)
+  if (env === 'production' || useBrowserSync === 'false') {
+    server.listen(port)
+  } else {
+    server.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'
+      })
+    })
+  }
+})

server.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')
 
@@ -96,12 +93,19 @@ var appViews = [
   path.join(__dirname, '/lib/')
 ]
 
-var nunjucksAppEnv = nunjucks.configure(appViews, {
+var nunjucksConfig = {
   autoescape: true,
-  express: app,
   noCache: true,
-  watch: true
-})
+  watch: false // We are now setting this to `false` (it's by default false anyway) as having it set to `true` for production was making the tests hang
+}
+
+if (env === 'development') {
+  nunjucksConfig.watch = true
+}
+
+nunjucksConfig.express = app
+
+var nunjucksAppEnv = nunjucks.configure(appViews, nunjucksConfig)
 
 // Add Nunjucks filters
 utils.addNunjucksFilters(nunjucksAppEnv)
@@ -125,12 +129,8 @@ if (useDocumentation) {
     path.join(__dirname, '/lib/')
   ]
 
-  var nunjucksDocumentationEnv = nunjucks.configure(documentationViews, {
-    autoescape: true,
-    express: documentationApp,
-    noCache: true,
-    watch: true
-  })
+  nunjucksConfig.express = documentationApp
+  var nunjucksDocumentationEnv = nunjucks.configure(documentationViews, nunjucksConfig)
   // Nunjucks filters
   utils.addNunjucksFilters(nunjucksDocumentationEnv)
 
@@ -151,13 +151,9 @@ if (useV6) {
     path.join(__dirname, '/app/v6/views/'),
     path.join(__dirname, '/lib/v6') // for old unbranded template
   ]
+  nunjucksConfig.express = v6App
+  var nunjucksV6Env = nunjucks.configure(v6Views, nunjucksConfig)
 
-  var nunjucksV6Env = nunjucks.configure(v6Views, {
-    autoescape: true,
-    express: v6App,
-    noCache: true,
-    watch: true
-  })
   // Nunjucks filters
   utils.addNunjucksFilters(nunjucksV6Env)
 
@@ -350,25 +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