Ensure i18n matches options (#2358)

* Add failing spec showing that human_locales does not match what i18n knows about

* Add missing `ar` key for arabic to human locales

* Remove duplicate `id` key from available locales

* Sort keys in human locales list

* Add spec for human_locale helper

spec/helpers/settings_helper_spec.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe SettingsHelper do
+  describe 'the HUMAN_LOCALES constant' do
+    it 'has the same number of keys as I18n locales exist' do
+      options = I18n.available_locales
+
+      expect(described_class::HUMAN_LOCALES.keys).to eq(options)
+    end
+  end
+
+  describe 'human_locale' do
+    it 'finds the human readable local description from a key' do
+      # Ensure the value is as we expect
+      expect(described_class::HUMAN_LOCALES[:en]).to eq('English')
+
+      expect(helper.human_locale(:en)).to eq('English')
+    end
+  end
+end