Fix broken spec due to last_activity_at updates being throttled

In https://gitlab.com/gitlab-org/gitlab-ce/builds/4218398, the build failed
because the last_activity_at column was only being updated once per hour. We
can fix this spec by stubbing out the throttling and adjusting the spec to
test the right event timestamp.

app/models/event.rb

@@ -330,13 +330,23 @@ class Event < ActiveRecord::Base
 
     # Don't even bother obtaining a lock if the last update happened less than
     # 60 minutes ago.
-    return if project.last_activity_at > RESET_PROJECT_ACTIVITY_INTERVAL.ago
+    return if recent_update?
 
-    return unless Gitlab::ExclusiveLease.
+    return unless try_obtain_lease
+
+    project.update_column(:last_activity_at, created_at)
+  end
+
+  private
+
+  def recent_update?
+    project.last_activity_at > RESET_PROJECT_ACTIVITY_INTERVAL.ago
+  end
+
+  def try_obtain_lease
+    Gitlab::ExclusiveLease.
       new("project:update_last_activity_at:#{project.id}",
           timeout: RESET_PROJECT_ACTIVITY_INTERVAL.to_i).
       try_obtain
-
-    project.update_column(:last_activity_at, created_at)
   end
 end

spec/factories/events.rb

 FactoryGirl.define do
   factory :event do
+    project
+    author factory: :user
+
     factory :closed_issue_event do
-      project
       action { Event::CLOSED }
       target factory: :closed_issue
-      author factory: :user
     end
   end
 end

spec/models/project_spec.rb

@@ -308,20 +308,23 @@ describe Project, models: true do
   end
 
   describe 'last_activity methods' do
-    let(:project) { create(:project) }
-    let(:last_event) { double(created_at: Time.now) }
+    let(:timestamp) { Time.now - 2.hours }
+    let(:project) { create(:project, created_at: timestamp, updated_at: timestamp) }
 
     describe 'last_activity' do
       it 'alias last_activity to last_event' do
-        allow(project).to receive(:last_event).and_return(last_event)
+        last_event = create(:event, project: project)
+
         expect(project.last_activity).to eq(last_event)
       end
     end
 
     describe 'last_activity_date' do
       it 'returns the creation date of the project\'s last event if present' do
-        create(:event, project: project)
-        expect(project.last_activity_at.to_i).to eq(last_event.created_at.to_i)
+        expect_any_instance_of(Event).to receive(:try_obtain_lease).and_return(true)
+        new_event = create(:event, project: project, created_at: Time.now)
+
+        expect(project.last_activity_at.to_i).to eq(new_event.created_at.to_i)
       end
 
       it 'returns the project\'s last update date if it has no events' do