Add an E2E test of PostReceive idempotency

qa/qa/resource/events/base.rb

@@ -24,6 +24,18 @@ module QA
           "#{api_get_path}/events"
         end
 
+        def fetch_events
+          events_returned = nil
+          Support::Waiter.wait_until(max_duration: max_wait, raise_on_failure: raise_on_failure) do
+            events_returned = yield
+            events_returned.any?
+          end
+
+          raise EventNotFoundError, "Timed out waiting for events" unless events_returned
+
+          events_returned
+        end
+
         def wait_for_event
           event_found = Support::Waiter.wait_until(max_duration: max_wait, raise_on_failure: raise_on_failure) do
             yield

qa/qa/resource/events/project.rb

@@ -6,6 +6,13 @@ module QA
       module Project
         include Events::Base
 
+        def push_events(commit_message)
+          QA::Runtime::Logger.debug(%Q[#{self.class.name} - wait for and fetch push events"])
+          fetch_events do
+            events(action: 'pushed').select { |event| event.dig(:push_data, :commit_title) == commit_message }
+          end
+        end
+
         def wait_for_merge(title)
           QA::Runtime::Logger.debug(%Q[#{self.class.name} - wait_for_merge with title "#{title}"])
           wait_for_event do

qa/qa/specs/features/api/3_create/repository/push_postreceive_idempotent_spec.rb

+# frozen_string_literal: true
+
+module QA
+  RSpec.describe 'Create' do
+    describe 'PostReceive idempotent' do
+      # Tests that a push does not result in multiple changes from repeated PostReceive executions.
+      # One of the consequences would be duplicate push events
+
+      let(:project) do
+        Resource::Project.fabricate_via_api! do |project|
+          project.name = 'push-postreceive-idempotent'
+          project.initialize_with_readme = true
+        end
+      end
+
+      after do
+        project&.remove_via_api!
+      end
+
+      it 'pushes and creates a single push event three times', testcase: 'https://gitlab.com/gitlab-org/quality/testcases/-/issues/1744' do
+        verify_single_event_per_push(repeat: 3)
+      end
+
+      it 'repeatedly pushes and creates a single push event several times', :transient, testcase: 'https://gitlab.com/gitlab-org/quality/testcases/-/issues/1744' do
+        verify_single_event_per_push(repeat: Runtime::Env.transient_trials) do |i|
+          QA::Runtime::Logger.info("Transient bug test action - Trial #{i}")
+        end
+      end
+
+      def verify_single_event_per_push(repeat:)
+        repeat.times do |i|
+          yield i if block_given?
+
+          commit_message = "test post-receive idempotency #{SecureRandom.hex(8)}"
+
+          Resource::Repository::ProjectPush.fabricate! do |push|
+            push.project = project
+            push.new_branch = false
+            push.commit_message = commit_message
+          end
+
+          events = project.push_events(commit_message)
+
+          aggregate_failures do
+            expect(events.size).to eq(1), "An unexpected number of push events was created"
+            expect(events.first.dig(:push_data, :commit_title)).to eq(commit_message)
+          end
+        end
+      end
+    end
+  end
+end