DEV: Add test for list_group_topics_assigned (#338)

Follow up to commit c8fc42b60f.

spec/lib/topic_query_spec.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+require 'topic_view'
+
+describe TopicQuery do
+  fab!(:user) { Fabricate(:user) }
+  fab!(:admin) { Fabricate(:admin) }
+  fab!(:other_admin) { Fabricate(:admin) }
+
+  fab!(:user_pm) { Fabricate(:private_message_topic, user: user) }
+  fab!(:admin_pm) { Fabricate(:private_message_topic, user: admin) }
+  fab!(:other_admin_pm) { Fabricate(:private_message_topic, user: other_admin) }
+
+  fab!(:group) { Fabricate(:group) }
+
+  describe '#list_group_topics_assigned' do
+    before do
+      SiteSetting.assign_enabled = true
+
+      [user, admin, other_admin].each do |user|
+        group.add(user)
+      end
+
+      [user_pm, admin_pm, other_admin_pm].each do |topic|
+        Fabricate(:post, topic: topic)
+      end
+
+      Assigner.new(user_pm, Discourse.system_user).assign(admin)
+      Assigner.new(admin_pm, Discourse.system_user).assign(admin)
+      Assigner.new(other_admin_pm, Discourse.system_user).assign(other_admin)
+    end
+
+    it "includes PMs from all users" do
+      expect(TopicQuery.new(user).list_group_topics_assigned(group).topics).to contain_exactly(user_pm)
+      expect(TopicQuery.new(admin).list_group_topics_assigned(group).topics).to contain_exactly(user_pm, admin_pm, other_admin_pm)
+      expect(TopicQuery.new(other_admin).list_group_topics_assigned(group).topics).to contain_exactly(user_pm, admin_pm, other_admin_pm)
+    end
+  end
+end