Add coverage for media#player, move body class to view (#31790)

spec/system/media_spec.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'Media' do
+  describe 'Player page' do
+    context 'when signed in' do
+      before { sign_in Fabricate(:user) }
+
+      it 'visits the media player page and renders the media' do
+        status = Fabricate :status
+        media = Fabricate :media_attachment, type: :video
+        status.media_attachments << media
+
+        visit medium_player_path(media)
+
+        expect(page)
+          .to have_css('body', class: 'player')
+          .and have_css('div[data-component="Video"]')
+      end
+    end
+  end
+end