Fulfill the tests for transaction instrumentations

spec/lib/gitlab/metrics/subscribers/active_record_spec.rb

@@ -8,6 +8,85 @@ RSpec.describe Gitlab::Metrics::Subscribers::ActiveRecord do
   let(:env) { {} }
   let(:subscriber) { described_class.new }
   let(:connection) { double(:connection) }
+
+  describe '#transaction' do
+    let(:web_transaction) { double('Gitlab::Metrics::WebTransaction') }
+    let(:background_transaction) { double('Gitlab::Metrics::WebTransaction') }
+
+    let(:event) do
+      double(
+        :event,
+        name: 'transaction.active_record',
+        duration: 230,
+        payload:  { connection: connection }
+      )
+    end
+
+    before do
+      allow(background_transaction).to receive(:observe)
+      allow(web_transaction).to receive(:observe)
+    end
+
+    context 'when both web and background transaction are available' do
+      before do
+        allow(::Gitlab::Metrics::WebTransaction).to receive(:current)
+          .and_return(web_transaction)
+        allow(::Gitlab::Metrics::BackgroundTransaction).to receive(:current)
+          .and_return(background_transaction)
+      end
+
+      it 'captures the metrics for web only' do
+        expect(web_transaction).to receive(:observe).with(:gitlab_database_transaction_seconds, 0.23)
+
+        expect(background_transaction).not_to receive(:observe)
+        expect(background_transaction).not_to receive(:increment)
+
+        subscriber.transaction(event)
+      end
+    end
+
+    context 'when web transaction is available' do
+      let(:web_transaction) { double('Gitlab::Metrics::WebTransaction') }
+
+      before do
+        allow(::Gitlab::Metrics::WebTransaction).to receive(:current)
+          .and_return(web_transaction)
+        allow(::Gitlab::Metrics::BackgroundTransaction).to receive(:current)
+          .and_return(nil)
+      end
+
+      it 'captures the metrics for web only' do
+        expect(web_transaction).to receive(:observe).with(:gitlab_database_transaction_seconds, 0.23)
+
+        expect(background_transaction).not_to receive(:observe)
+        expect(background_transaction).not_to receive(:increment)
+
+        subscriber.transaction(event)
+      end
+    end
+
+    context 'when background transaction is available' do
+      let(:background_transaction) { double('Gitlab::Metrics::BackgroundTransaction') }
+
+      before do
+        allow(::Gitlab::Metrics::WebTransaction).to receive(:current)
+          .and_return(nil)
+        allow(::Gitlab::Metrics::BackgroundTransaction).to receive(:current)
+          .and_return(background_transaction)
+      end
+
+      it 'captures the metrics for web only' do
+        expect(background_transaction).to receive(:observe).with(:gitlab_database_transaction_seconds, 0.23)
+
+        expect(web_transaction).not_to receive(:observe)
+        expect(web_transaction).not_to receive(:increment)
+
+        subscriber.transaction(event)
+      end
+    end
+  end
+
+  describe '#sql' do
     let(:payload) { { sql: 'SELECT * FROM users WHERE id = 10', connection: connection } }
 
     let(:event) do
@@ -69,4 +148,5 @@ RSpec.describe Gitlab::Metrics::Subscribers::ActiveRecord do
 
       it_behaves_like 'track generic sql events'
     end
+  end
 end