2 files changed, 26 insertions, 0 deletions
diff --git a/spec/services/merge_requests/merge_service_spec.rb b/spec/services/merge_requests/merge_service_spec.rb
index aa759ac9edc..22578436c18 100644
--- a/spec/services/merge_requests/merge_service_spec.rb
+++ b/spec/services/merge_requests/merge_service_spec.rb
@@ -214,6 +214,19 @@ describe MergeRequests::MergeService do
         allow(Rails.logger).to receive(:error)
       end
 
+      context 'when source is missing' do
+        it 'logs and saves error' do
+          allow(merge_request).to receive(:diff_head_sha) { nil }
+
+          error_message = 'No source for merge'
+
+          service.execute(merge_request)
+
+          expect(merge_request.merge_error).to eq(error_message)
+          expect(Rails.logger).to have_received(:error).with(a_string_matching(error_message))
+        end
+      end
+
       it 'logs and saves error if there is an exception' do
         error_message = 'error message'
 
diff --git a/spec/services/merge_requests/merge_to_ref_service_spec.rb b/spec/services/merge_requests/merge_to_ref_service_spec.rb
index 14012b4ea2d..758679edc45 100644
--- a/spec/services/merge_requests/merge_to_ref_service_spec.rb
+++ b/spec/services/merge_requests/merge_to_ref_service_spec.rb
@@ -191,6 +191,19 @@ describe MergeRequests::MergeToRefService do
       it { expect(todo).not_to be_done }
     end
 
+    context 'when source is missing' do
+      it 'returns error' do
+        allow(merge_request).to receive(:diff_head_sha) { nil }
+
+        error_message = 'No source for merge'
+
+        result = service.execute(merge_request)
+
+        expect(result[:status]).to eq(:error)
+        expect(result[:message]).to eq(error_message)
+      end
+    end
+
     context 'when target ref is passed as a parameter' do
       let(:params) { { commit_message: 'merge train', target_ref: target_ref } }