1 files changed, 75 insertions, 0 deletions
diff --git a/spec/lib/gitlab/usage/metrics/instrumentations/database_metric_spec.rb b/spec/lib/gitlab/usage/metrics/instrumentations/database_metric_spec.rb
new file mode 100644
index 00000000000..5e36820df5e
--- /dev/null
+++ b/spec/lib/gitlab/usage/metrics/instrumentations/database_metric_spec.rb
@@ -0,0 +1,75 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Usage::Metrics::Instrumentations::DatabaseMetric do
+  subject do
+    described_class.tap do |m|
+      m.relation { Issue }
+      m.operation :count
+      m.start { m.relation.minimum(:id) }
+      m.finish { m.relation.maximum(:id) }
+    end.new(time_frame: 'all')
+  end
+
+  describe '#value' do
+    let_it_be(:issue_1) { create(:issue) }
+    let_it_be(:issue_2) { create(:issue) }
+    let_it_be(:issue_3) { create(:issue) }
+    let_it_be(:issues) { Issue.all }
+
+    before do
+      allow(ActiveRecord::Base.connection).to receive(:transaction_open?).and_return(false)
+    end
+
+    it 'calculates a correct result' do
+      expect(subject.value).to eq(3)
+    end
+
+    it 'does not cache the result of start and finish', :request_store, :use_clean_rails_redis_caching do
+      expect(Gitlab::Cache).not_to receive(:fetch_once)
+      expect(subject).to receive(:count).with(any_args, hash_including(start: issues.min_by(&:id).id, finish: issues.max_by(&:id).id)).and_call_original
+
+      subject.value
+
+      expect(Rails.cache.read('metric_instrumentation/special_issue_count_minimum_id')).to eq(nil)
+      expect(Rails.cache.read('metric_instrumentation/special_issue_count_maximum_id')).to eq(nil)
+    end
+
+    context 'with start and finish not called' do
+      subject do
+        described_class.tap do |m|
+          m.relation { Issue }
+          m.operation :count
+        end.new(time_frame: 'all')
+      end
+
+      it 'calculates a correct result' do
+        expect(subject.value).to eq(3)
+      end
+    end
+
+    context 'with cache_start_and_finish_as called' do
+      subject do
+        described_class.tap do |m|
+          m.relation { Issue }
+          m.operation :count
+          m.start { m.relation.minimum(:id) }
+          m.finish { m.relation.maximum(:id) }
+          m.cache_start_and_finish_as :special_issue_count
+        end.new(time_frame: 'all')
+      end
+
+      it 'caches using the key name passed', :request_store, :use_clean_rails_redis_caching do
+        expect(Gitlab::Cache).to receive(:fetch_once).with('metric_instrumentation/special_issue_count_minimum_id', any_args).and_call_original
+        expect(Gitlab::Cache).to receive(:fetch_once).with('metric_instrumentation/special_issue_count_maximum_id', any_args).and_call_original
+        expect(subject).to receive(:count).with(any_args, hash_including(start: issues.min_by(&:id).id, finish: issues.max_by(&:id).id)).and_call_original
+
+        subject.value
+
+        expect(Rails.cache.read('metric_instrumentation/special_issue_count_minimum_id')).to eq(issues.min_by(&:id).id)
+        expect(Rails.cache.read('metric_instrumentation/special_issue_count_maximum_id')).to eq(issues.max_by(&:id).id)
+      end
+    end
+  end
+end