Add simple test for reverting_merge_request

spec/models/merge_request_spec.rb

@@ -2413,6 +2413,64 @@ RSpec.describe MergeRequest, factory_default: :keep do
     end
   end
 
+  describe '#reverting_merge_request' do
+    subject { create(:merge_request, source_project: create(:project, :repository)) }
+
+    context 'when there is no merge_commit for the MR' do
+      before do
+        subject.metrics.update!(merged_at: Time.current.utc)
+      end
+
+      it 'returns nil' do
+        expect(subject.reverting_merge_request(nil)).to be_nil
+      end
+    end
+
+    context 'when the MR has been merged' do
+      before do
+        MergeRequests::MergeService
+          .new(subject.target_project, subject.author, { sha: subject.diff_head_sha })
+          .execute(subject)
+      end
+
+      context 'when there is no revert commit' do
+        it 'returns nil' do
+          expect(subject.reverting_merge_request(nil)).to be_nil
+        end
+      end
+
+      context 'when there is no merged_at for the MR' do
+        before do
+          subject.metrics.update!(merged_at: nil)
+        end
+
+        it 'returns nil' do
+          expect(subject.reverting_merge_request(nil)).to be_nil
+        end
+      end
+
+      context 'when there is a revert commit by MR' do
+        let(:current_user) { subject.author }
+        let(:branch) { subject.target_branch }
+        let(:project) { subject.target_project }
+
+        let(:revert_commit_id) do
+          params = {
+            commit: subject.merge_commit,
+            branch_name: branch,
+            start_branch: branch
+          }
+
+          Commits::RevertService.new(project, current_user, params).execute[:result]
+        end
+
+        it 'returns nil' do
+          expect(subject.reverting_merge_request(current_user)).to be_nil
+        end
+      end
+    end
+  end
+
   describe '#can_be_reverted?' do
     subject { create(:merge_request, source_project: create(:project, :repository)) }