Adds project changelog

ee/changelogs/unreleased/12996-cancel-redundant-pipelines.yml

+---
+title: Cancel redundant merge train pipelines
+merge_request: 15450
+author:
+type: added

ee/spec/services/merge_trains/refresh_merge_request_service_spec.rb

@@ -40,7 +40,7 @@ describe MergeTrains::RefreshMergeRequestService do
 
       it do
         expect_next_instance_of(MergeTrains::CreatePipelineService, project, maintainer) do |pipeline_service|
-          allow(pipeline_service).to receive(:execute) { { status: :success, pipeline: pipeline } }
+          allow(pipeline_service).to receive(:execute) { { status: :success, pipeline: create(:ci_pipeline) } }
           expect(pipeline_service).to receive(:execute).with(merge_request, previous_ref)
         end
 
@@ -60,6 +60,12 @@ describe MergeTrains::RefreshMergeRequestService do
       end
     end
 
+    shared_examples_for 'cancels the old pipeline for merge train' do
+      it do
+        expect { subject }.to change { pipeline.reload.status }.to('canceled')
+      end
+    end
+
     context 'when merge train project configuration is disabled' do
       before do
         project.update!(merge_trains_enabled: false)
@@ -137,7 +143,7 @@ describe MergeTrains::RefreshMergeRequestService do
     end
 
     context 'when pipeline for merge train is running' do
-      let(:pipeline) { create(:ci_pipeline, :running, target_sha: previous_ref_sha, source_sha: merge_request.diff_head_sha) }
+      let(:pipeline) { create(:ci_pipeline, :running, :with_job, target_sha: previous_ref_sha, source_sha: merge_request.diff_head_sha) }
       let(:previous_ref_sha) { project.repository.commit('refs/heads/master').sha }
 
       before do
@@ -151,12 +157,14 @@ describe MergeTrains::RefreshMergeRequestService do
       context 'when the pipeline is stale' do
         let(:previous_ref_sha) { project.repository.commits('refs/heads/master', limit: 2).last.sha }
 
+        it_behaves_like 'cancels the old pipeline for merge train'
         it_behaves_like 'creates a pipeline for merge train'
       end
 
-      context 'when the pipeline is reuired to be recreated' do
+      context 'when the pipeline is required to be recreated' do
         let(:require_recreate) { true }
 
+        it_behaves_like 'cancels the old pipeline for merge train'
         it_behaves_like 'creates a pipeline for merge train'
       end
     end