#332

backend/spec/models/tag_implication_spec.rb

@@ -0,0 +1,36 @@
+require 'rails_helper'
+
+RSpec.describe TagImplication, type: :model do
+  it 'rejects a parent tag that would create a cycle' do
+    child = create(:tag, name: 'tag_implication_cycle_child')
+    parent = create(:tag, name: 'tag_implication_cycle_parent')
+
+    described_class.create!(tag: child, parent_tag: parent)
+
+    implication = described_class.new(tag: parent, parent_tag: child)
+
+    expect(implication).not_to be_valid
+    expect(implication.errors[:parent_tag_id]).to include(
+      '親タグに子孫タグを指定すると循環します．'
+    )
+    expect(implication.errors[:base]).to be_present
+  end
+
+  it 'terminates even when existing data already contains a cycle' do
+    child = create(:tag, name: 'tag_implication_existing_cycle_child')
+    parent = create(:tag, name: 'tag_implication_existing_cycle_parent')
+    ancestor = create(:tag, name: 'tag_implication_existing_cycle_ancestor')
+
+    described_class.create!(tag: parent, parent_tag: ancestor)
+    described_class.insert_all!(
+      [
+        { tag_id: ancestor.id, parent_tag_id: parent.id,
+          created_at: Time.current, updated_at: Time.current }
+      ]
+    )
+
+    implication = described_class.new(tag: child, parent_tag: parent)
+
+    expect(implication).to be_valid
+  end
+end

backend/spec/models/tag_spec.rb

@@ -54,7 +54,17 @@ RSpec.describe Tag, type: :model do
       first = create(:tag, name: 'expand_cycle_first')
       second = create(:tag, name: 'expand_cycle_second')
       TagImplication.create!(tag: first, parent_tag: second)
-      TagImplication.create!(tag: second, parent_tag: first)
+      now = Time.current
+      TagImplication.insert_all!(
+        [
+          {
+            tag_id: second.id,
+            parent_tag_id: first.id,
+            created_at: now,
+            updated_at: now
+          }
+        ]
+      )
 
       expect(described_class.expand_parent_tags([first])).to contain_exactly(first, second)
     end