1 files changed, 69 insertions, 0 deletions
diff --git a/spec/serializers/merge_request_metrics_helper_spec.rb b/spec/serializers/merge_request_metrics_helper_spec.rb
new file mode 100644
index 00000000000..8f683df1faa
--- /dev/null
+++ b/spec/serializers/merge_request_metrics_helper_spec.rb
@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe MergeRequestMetricsHelper do
+  let_it_be(:user) { create(:user) }
+
+  let(:merge_request) { create(:merge_request) }
+  let(:helper) { Class.new.include(described_class).new }
+
+  describe '#build_metrics' do
+    subject do
+      helper.build_metrics(merge_request)
+    end
+
+    shared_examples 'does not rebuild the metrics' do
+      it 'does not call the merge request metrics class' do
+        expect(MergeRequest::Metrics).not_to receive(:new)
+
+        subject
+      end
+
+      it 'returns the metrics for the given merge request' do
+        expect(subject).to be_kind_of(MergeRequest::Metrics)
+        expect(subject[:merge_request_id]).to eq(merge_request.id)
+      end
+    end
+
+    context 'when closed and metrics exists' do
+      before do
+        merge_request.close!
+        merge_request.metrics.update!(latest_closed_by: user)
+      end
+
+      include_examples 'does not rebuild the metrics'
+    end
+
+    context 'when merged and metrics exists' do
+      before do
+        merge_request.mark_as_merged!
+        merge_request.metrics.update!(merged_by: user)
+      end
+
+      include_examples 'does not rebuild the metrics'
+    end
+
+    context 'when merged and metrics do not exists' do
+      before do
+        merge_request.mark_as_merged!
+        merge_request.metrics.destroy!
+        merge_request.reload
+      end
+
+      it 'rebuilds the merge request metrics' do
+        closed_event = merge_request.closed_event
+        merge_event = merge_request.merge_event
+
+        expect(MergeRequest::Metrics).to receive(:new)
+            .with(latest_closed_at: closed_event&.updated_at,
+              latest_closed_by: closed_event&.author,
+              merged_at: merge_event&.updated_at,
+              merged_by: merge_event&.author)
+            .and_call_original
+
+        subject
+      end
+    end
+  end
+end