Convert tags controller spec to system and request specs (#31708)

spec/requests/tags_spec.rb

@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'Tags' do
+  describe 'GET /tags/:id' do
+    context 'when tag exists' do
+      let(:tag) { Fabricate :tag }
+
+      context 'with HTML format' do
+        # TODO: Convert the cacheable response shared example into a matcher,
+        # remove this example, rely on system spec (which should use matcher)
+        before { get tag_path(tag) }
+
+        it 'returns http success' do
+          expect(response)
+            .to have_http_status(200)
+        end
+
+        it_behaves_like 'cacheable response', expects_vary: 'Accept, Accept-Language, Cookie'
+      end
+
+      context 'with JSON format' do
+        before { get tag_path(tag, format: :json) }
+
+        it 'returns http success' do
+          expect(response)
+            .to have_http_status(200)
+          expect(response.content_type)
+            .to start_with('application/activity+json')
+        end
+
+        it_behaves_like 'cacheable response', expects_vary: 'Accept, Accept-Language, Cookie'
+      end
+
+      context 'with RSS format' do
+        before { get tag_path(tag, format: :rss) }
+
+        it 'returns http success' do
+          expect(response)
+            .to have_http_status(200)
+          expect(response.content_type)
+            .to start_with('application/rss+xml')
+        end
+
+        it_behaves_like 'cacheable response', expects_vary: 'Accept, Accept-Language, Cookie'
+      end
+    end
+
+    context 'when tag does not exist' do
+      before { get tag_path('missing') }
+
+      it 'returns http not found' do
+        expect(response)
+          .to have_http_status(404)
+      end
+    end
+  end
+end