1 files changed, 62 insertions, 7 deletions
diff --git a/spec/services/auto_merge_service_spec.rb b/spec/services/auto_merge_service_spec.rb
index 221cf695331..bab69fb4aa3 100644
--- a/spec/services/auto_merge_service_spec.rb
+++ b/spec/services/auto_merge_service_spec.rb
@@ -3,22 +3,36 @@
 require 'spec_helper'
 
 describe AutoMergeService do
-  let_it_be(:project) { create(:project) }
+  let_it_be(:project) { create(:project, :repository) }
   let_it_be(:user) { create(:user) }
   let(:service) { described_class.new(project, user) }
 
-  describe '.all_strategies' do
-    subject { described_class.all_strategies }
+  before_all do
+    project.add_maintainer(user)
+  end
 
-    it 'includes merge when pipeline succeeds' do
-      is_expected.to include(AutoMergeService::STRATEGY_MERGE_WHEN_PIPELINE_SUCCEEDS)
+  describe '.all_strategies_ordered_by_preference' do
+    subject { described_class.all_strategies_ordered_by_preference }
+
+    it 'returns all strategies in preference order' do
+      if Gitlab.ee?
+        is_expected.to eq(
+          [AutoMergeService::STRATEGY_MERGE_TRAIN,
+           AutoMergeService::STRATEGY_ADD_TO_MERGE_TRAIN_WHEN_PIPELINE_SUCCEEDS,
+           AutoMergeService::STRATEGY_MERGE_WHEN_PIPELINE_SUCCEEDS])
+      else
+        is_expected.to eq([AutoMergeService::STRATEGY_MERGE_WHEN_PIPELINE_SUCCEEDS])
+      end
     end
   end
 
   describe '#available_strategies' do
     subject { service.available_strategies(merge_request) }
 
-    let(:merge_request) { create(:merge_request) }
+    let(:merge_request) do
+      create(:merge_request, source_project: project)
+    end
+
     let(:pipeline_status) { :running }
 
     before do
@@ -42,6 +56,36 @@ describe AutoMergeService do
     end
   end
 
+  describe '#preferred_strategy' do
+    subject { service.preferred_strategy(merge_request) }
+
+    let(:merge_request) do
+      create(:merge_request, source_project: project)
+    end
+
+    let(:pipeline_status) { :running }
+
+    before do
+      create(:ci_pipeline, pipeline_status, ref: merge_request.source_branch,
+                                            sha: merge_request.diff_head_sha,
+                                            project: merge_request.source_project)
+
+      merge_request.update_head_pipeline
+    end
+
+    it 'returns preferred strategy' do
+      is_expected.to eq('merge_when_pipeline_succeeds')
+    end
+
+    context 'when the head piipeline succeeded' do
+      let(:pipeline_status) { :success }
+
+      it 'returns available strategies' do
+        is_expected.to be_nil
+      end
+    end
+  end
+
   describe '.get_service_class' do
     subject { described_class.get_service_class(strategy) }
 
@@ -63,7 +107,10 @@ describe AutoMergeService do
   describe '#execute' do
     subject { service.execute(merge_request, strategy) }
 
-    let(:merge_request) { create(:merge_request) }
+    let(:merge_request) do
+      create(:merge_request, source_project: project)
+    end
+
     let(:pipeline_status) { :running }
     let(:strategy) { AutoMergeService::STRATEGY_MERGE_WHEN_PIPELINE_SUCCEEDS }
 
@@ -90,6 +137,14 @@ describe AutoMergeService do
         is_expected.to eq(:failed)
       end
     end
+
+    context 'when strategy is not specified' do
+      let(:strategy) { }
+
+      it 'chooses the most preferred strategy' do
+        is_expected.to eq(:merge_when_pipeline_succeeds)
+      end
+    end
   end
 
   describe '#update' do