Add tests for pushing build to a queue

app/models/ci/build.rb

@@ -37,6 +37,7 @@ module Ci
 
     has_one :deployment, as: :deployable, class_name: 'Deployment'
     has_one :pending_state, class_name: 'Ci::BuildPendingState', inverse_of: :build
+    has_one :queuing_entry, class_name: 'Ci::PendingBuild', foreign_key: :build_id
     has_many :trace_sections, class_name: 'Ci::BuildTraceSection'
     has_many :trace_chunks, class_name: 'Ci::BuildTraceChunk', foreign_key: :build_id, inverse_of: :build
     has_many :report_results, class_name: 'Ci::BuildReportResult', inverse_of: :build

spec/models/ci/build_spec.rb

@@ -323,8 +323,6 @@ RSpec.describe Ci::Build do
   describe '#enqueue' do
     let(:build) { create(:ci_build, :created) }
 
-    subject { build.enqueue }
-
     before do
       allow(build).to receive(:any_unmet_prerequisites?).and_return(has_prerequisites)
       allow(Ci::PrepareBuildService).to receive(:perform_async)
@@ -334,20 +332,45 @@ RSpec.describe Ci::Build do
       let(:has_prerequisites) { true }
 
       it 'transitions to preparing' do
-        subject
+        build.enqueue
 
         expect(build).to be_preparing
       end
+
+      it 'does not push build to the queue' do
+        build.enqueue
+
+        expect(::Ci::PendingBuild.all.count).to be_zero
+      end
     end
 
     context 'build has no prerequisites' do
       let(:has_prerequisites) { false }
 
       it 'transitions to pending' do
-        subject
+        build.enqueue
 
         expect(build).to be_pending
       end
+
+      it 'pushed build to a queue' do
+        build.enqueue
+
+        expect(build.queuing_entry).to be_present
+      end
+
+      context 'when build status transition fails' do
+        before do
+          ::Ci::Build.find(build.id).update_column(:lock_version, 100)
+        end
+
+        it 'does not push build to a queue' do
+          expect { build.enqueue }
+            .to raise_error(ActiveRecord::StaleObjectError)
+
+          expect(build.queuing_entry).not_to be_present
+        end
+      end
     end
   end
 

spec/services/ci/retry_build_service_spec.rb

@@ -59,7 +59,8 @@ RSpec.describe Ci::RetryBuildService do
        metadata runner_session trace_chunks upstream_pipeline_id
        artifacts_file artifacts_metadata artifacts_size commands
        resource resource_group_id processed security_scans author
-       pipeline_id report_results pending_state pages_deployments].freeze
+       pipeline_id report_results pending_state pages_deployments
+       queuing_entry].freeze
 
   shared_examples 'build duplication' do
     let_it_be(:another_pipeline) { create(:ci_empty_pipeline, project: project) }