Improved test for variant serializer

spec/serializers/variant_serializer_spec.rb

@@ -1,13 +1,27 @@
 require 'spec_helper'
 
 describe Api::VariantSerializer do
-  let(:serializer) { Api::VariantSerializer.new variant }
+  
+  subject { Api::VariantSerializer.new variant }
   let(:variant) { create(:variant) }
 
-
-  it "serializes a variant" do
-    expect(serializer.to_json).to match variant.id.to_s
+  it "includes the expected attributes " do 
+    expect(subject.attributes.keys).
+    to include(
+        :id,
+        :name_to_display, 
+        :is_master, 
+        :count_on_hand, 
+        :name_to_display, 
+        :unit_to_display, 
+        :unit_value,
+        :options_text, 
+        :on_demand, 
+        :price, 
+        :fees, 
+        :price_with_fees, 
+        :product_name
+      )
   end
 
-
 end