Adds locale switcher js code + feature tests

app/assets/javascripts/locale_switcher.js.coffee

@@ -0,0 +1,19 @@
+App.LocaleSwitcher =
+
+  href_with_params: (query_params) ->
+    loc = window.location
+
+    loc.protocol + "//" + loc.hostname +
+      (if loc.port then ':' + loc.port else '') +
+      loc.pathname +
+      loc.hash +
+      '?' + $.param(query_params)
+
+  initialize: ->
+    $('.js-locale-switcher').on 'change', ->
+      query_params = window.getQueryParameters()
+      query_params['locale'] = $(this).val()
+      window.location.assign(App.LocaleSwitcher.href_with_params(query_params))
+
+
+

spec/features/locale_switcher_spec.rb

@@ -0,0 +1,29 @@
+require 'rails_helper'
+
+feature 'Locale Switcher' do
+
+  scenario 'Available locales appear in the locale switcher' do
+    visit '/'
+
+    within('.js-locale-switcher') do
+      expect(page).to have_content 'Español'
+      expect(page).to have_content 'English'
+    end
+  end
+
+  scenario 'The current locale is selected' do
+    visit '/'
+    expect(page).to have_select('locale-switcher', selected: 'English')
+  end
+
+  scenario 'Changing the locale', :js do
+    visit '/'
+    expect(page).to have_content('Site language')
+
+    select('Español', from: 'locale-switcher')
+    expect(page).to have_content('Idioma de la página')
+    expect(page).to_not have_content('Site language')
+    expect(page).to have_select('locale-switcher', selected: 'Español')
+  end
+
+end