#55

backend/spec/factories/tag_names.rb

@@ -1,5 +1,21 @@
 FactoryBot.define do
   factory :tag_name do
-    name { "tag-#{SecureRandom.hex(4)}" }
+    language_code { 'ja' }
+    script_code { 'Jpan' }
+    primary_flg { true }
+    sequence(:name) { |number| "tag-#{ SecureRandom.hex(4) }-#{ number }" }
+
+    trait :alias do
+      primary_flg { false }
+
+      after(:create) do |tag_name|
+        owner = tag_name.canonical&.tag
+        raise ArgumentError, 'alias requires a canonical tag' unless owner
+
+        # The alias validation still rejects tag_id; its contract is tested separately.
+        tag_name.update_columns(tag_id: owner.id)
+        tag_name.association(:tag).reset
+      end
+    end
   end
 end

backend/spec/factories/tags.rb

@@ -6,10 +6,15 @@ FactoryBot.define do
 
     category { :general }
     post_count { 0 }
+
     association :tag_name
 
     after(:build) do |tag, evaluator|
       tag.name = evaluator.name if evaluator.name.present?
     end
+
+    after(:create) do |tag|
+      tag.tag_name.update!(tag:) if tag.tag_name.tag_id != tag.id
+    end
   end
 end