update units list on Spree::Admin::GeneralSettingsHelper#all_units

added a test to make sure that all units on WeightsAndMeasures::UNITS are list on all_units

app/helpers/spree/admin/general_settings_helper.rb

@@ -4,7 +4,12 @@ module Spree
   module Admin
     module GeneralSettingsHelper
       def all_units
-        ["g", "oz", "lb", "kg", "T", "mL", "L", "kL"]
+        [
+          "mg", "g", "kg", "T",
+          "oz", "lb",
+          "mL", "cL", "dL", "L", "kL",
+          "gal"
+        ]
       end
     end
   end

spec/services/weights_and_measures_spec.rb

@@ -90,4 +90,12 @@ describe WeightsAndMeasures do
       end
     end
   end
+
+  describe "UNITS" do
+    include Spree::Admin::GeneralSettingsHelper
+    it "should include all the available untis" do
+      units = WeightsAndMeasures::UNITS.values.flat_map(&:values).pluck("name").sort.uniq
+      expect(units).to eq(all_units.sort.uniq)
+    end
+  end
 end