Add coverage for `Tag.recently_used` scope (#28850)

app/models/tag.rb

@@ -39,6 +39,8 @@ class Tag < ApplicationRecord
   HASHTAG_NAME_RE = /\A(#{HASHTAG_NAME_PAT})\z/i
   HASHTAG_INVALID_CHARS_RE = /[^[:alnum:]\u0E47-\u0E4E#{HASHTAG_SEPARATORS}]/
 
+  RECENT_STATUS_LIMIT = 1000
+
   validates :name, presence: true, format: { with: HASHTAG_NAME_RE }
   validates :display_name, format: { with: HASHTAG_NAME_RE }
   validate :validate_name_change, if: -> { !new_record? && name_changed? }
@@ -53,7 +55,7 @@ class Tag < ApplicationRecord
   scope :not_trendable, -> { where(trendable: false) }
   scope :recently_used, lambda { |account|
                           joins(:statuses)
-                            .where(statuses: { id: account.statuses.select(:id).limit(1000) })
+                            .where(statuses: { id: account.statuses.select(:id).limit(RECENT_STATUS_LIMIT) })
                             .group(:id).order(Arel.sql('count(*) desc'))
                         }
   scope :matches_name, ->(term) { where(arel_table[:name].lower.matches(arel_table.lower("#{sanitize_sql_like(Tag.normalize(term))}%"), nil, true)) } # Search with case-sensitive to use B-tree index

spec/models/tag_spec.rb

@@ -100,6 +100,38 @@ RSpec.describe Tag do
     end
   end
 
+  describe '.recently_used' do
+    let(:account) { Fabricate(:account) }
+    let(:other_person_status) { Fabricate(:status) }
+    let(:out_of_range) { Fabricate(:status, account: account) }
+    let(:older_in_range) { Fabricate(:status, account: account) }
+    let(:newer_in_range) { Fabricate(:status, account: account) }
+    let(:unused_tag) { Fabricate(:tag) }
+    let(:used_tag_one) { Fabricate(:tag) }
+    let(:used_tag_two) { Fabricate(:tag) }
+    let(:used_tag_on_out_of_range) { Fabricate(:tag) }
+
+    before do
+      stub_const 'Tag::RECENT_STATUS_LIMIT', 2
+
+      other_person_status.tags << used_tag_one
+
+      out_of_range.tags << used_tag_on_out_of_range
+
+      older_in_range.tags << used_tag_one
+      older_in_range.tags << used_tag_two
+
+      newer_in_range.tags << used_tag_one
+    end
+
+    it 'returns tags used by account within last X statuses ordered most used first' do
+      results = described_class.recently_used(account)
+
+      expect(results)
+        .to eq([used_tag_one, used_tag_two])
+    end
+  end
+
   describe '.find_normalized' do
     it 'returns tag for a multibyte case-insensitive name' do
       upcase_string   = 'abcABCａｂｃＡＢＣやゆよ'