update specs; add specs to validate weight calculator preference is kg or lb

app/models/calculator/weight.rb

@@ -3,7 +3,6 @@ require 'spree/localized_number'
 module Calculator
   class Weight < Spree::Calculator
     extend Spree::LocalizedNumber
-    
     preference :unit_from_list, :string, default: "kg"
     preference :per_unit, :decimal, default: 0.0
 
@@ -13,6 +12,14 @@ module Calculator
       I18n.t('spree.weight')
     end
 
+    def set_preference(name, value)
+      if name == :unit_from_list && !["kg", "lb"].include?(value)
+        self.calculable.errors.add(:preferred_unit_from_list, "must be kg or lb")
+      else
+        send self.class.preference_setter_method(name), value
+      end
+    end
+
     def compute(object)
       line_items = line_items_for object
       (total_weight(line_items) * preferred_per_unit).round(2)
@@ -76,9 +83,9 @@ module Calculator
     def convert_weight(value)
       return 0 unless value
 
-      if preferences[:unit] == "kg"
+      if preferences[:unit_from_list] == "kg"
         value / 1000
-      elsif preferences[:unit] == "lb"
+      elsif preferences[:unit_from_list] == "lb"
         value / 453.6
       else
         raise "Unknown unit preference"

spec/models/calculator/weight_spec.rb

@@ -15,7 +15,7 @@ describe Calculator::Weight do
     order = double(:order, line_items: [line_item1, line_item2, line_item3])
 
     subject.set_preference(:per_unit, 5)
-    subject.set_preference(:unit, "kg")
+    subject.set_preference(:unit_from_list, "kg")
     expect(subject.compute(order)).to eq(350) # (10 * 1 + 20 * 3) * 5
   end
 
@@ -25,7 +25,7 @@ describe Calculator::Weight do
 
     before {
       subject.set_preference(:per_unit, 5)
-      subject.set_preference(:unit, "kg")
+      subject.set_preference(:unit_from_list, "kg")
     }
 
     it "computes shipping cost for a line item" do
@@ -60,7 +60,7 @@ describe Calculator::Weight do
     object_with_order = double(:object_with_order, order: order)
 
     subject.set_preference(:per_unit, 5)
-    subject.set_preference(:unit, "kg")
+    subject.set_preference(:unit_from_list, "kg")
     expect(subject.compute(object_with_order)).to eq(250) # (10 * 1 + 20 * 2) * 5
   end
 
@@ -68,7 +68,7 @@ describe Calculator::Weight do
     let!(:product) { create(:product, product_attributes) }
     let!(:variant) { create(:variant, variant_attributes.merge(product: product)) }
 
-    let(:calculator) { described_class.new(preferred_per_unit: 6, preferred_unit: "kg") }
+    let(:calculator) { described_class.new(preferred_per_unit: 6, preferred_unit_from_list: "kg") }
     let(:line_item) do
       create(:line_item, variant: variant, quantity: 2).tap do |object|
         object.send(:calculate_final_weight_volume)
@@ -165,7 +165,7 @@ describe Calculator::Weight do
 
     before {
       subject.set_preference(:per_unit, 5)
-      subject.set_preference(:unit, "kg")
+      subject.set_preference(:unit_from_list, "kg")
     }
 
     context "when unit_value is zero variant.weight is present" do
@@ -208,4 +208,18 @@ describe Calculator::Weight do
       end
     end
   end
+
+  it "allows a preferred_unit of 'kg' and 'lb'" do
+    subject.calculable = build(:shipping_method)
+    subject.set_preference(:per_unit, 5)
+    subject.set_preference(:unit_from_list, "kg")
+    expect(subject.calculable.errors.count).to eq(0)
+  end
+
+  it "does not allow a preferred_unit of anything but 'kg' or 'lb'" do
+    subject.calculable = build(:shipping_method)
+    subject.set_preference(:per_unit, 5)
+    subject.set_preference(:unit_from_list, "kb")
+    expect(subject.calculable.errors.count).to eq(1)
+  end
 end