Fix #3937: Blank lines in tagbox if certain taggroups are absent

test/unit/tag_set_presenter_test.rb

@@ -0,0 +1,27 @@
+require 'test_helper'
+
+class TagSetPresenterTest < ActiveSupport::TestCase
+  context "TagSetPresenter" do
+    setup do
+      FactoryBot.create(:tag, name: "bkub", category: Tag.categories.artist)
+      FactoryBot.create(:tag, name: "chen", category: Tag.categories.character)
+      FactoryBot.create(:tag, name: "cirno", category: Tag.categories.character)
+      FactoryBot.create(:tag, name: "solo", category: Tag.categories.general)
+      FactoryBot.create(:tag, name: "touhou", category: Tag.categories.copyright)
+
+      @categories = %w[copyright character artist meta general]
+    end
+
+    context "#split_tag_list_text method" do
+      should "list all categories in order" do
+        text = TagSetPresenter.new(%w[bkub chen cirno solo touhou]).split_tag_list_text(category_list: @categories)
+        assert_equal("touhou \nchen cirno \nbkub \nsolo", text)
+      end
+
+      should "skip empty categories" do
+        text = TagSetPresenter.new(%w[bkub solo]).split_tag_list_text(category_list: @categories)
+        assert_equal("bkub \nsolo", text)
+      end
+    end
+  end
+end