1 files changed, 162 insertions, 0 deletions
diff --git a/spec/lib/gitlab/cache/client_spec.rb b/spec/lib/gitlab/cache/client_spec.rb
new file mode 100644
index 00000000000..638fed1a905
--- /dev/null
+++ b/spec/lib/gitlab/cache/client_spec.rb
@@ -0,0 +1,162 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Cache::Client, feature_category: :source_code_management do
+  subject(:client) { described_class.new(metadata, backend: backend) }
+
+  let(:backend) { Rails.cache }
+  let(:metadata) do
+    Gitlab::Cache::Metadata.new(
+      cache_identifier: cache_identifier,
+      feature_category: feature_category,
+      backing_resource: backing_resource
+    )
+  end
+
+  let(:cache_identifier) { 'MyClass#cache' }
+  let(:feature_category) { :source_code_management }
+  let(:backing_resource) { :cpu }
+
+  let(:metadata_mock) do
+    Gitlab::Cache::Metadata.new(
+      cache_identifier: cache_identifier,
+      feature_category: feature_category
+    )
+  end
+
+  let(:metrics_mock) { Gitlab::Cache::Metrics.new(metadata_mock) }
+
+  describe '.build_with_metadata' do
+    it 'builds a cache client with metrics support' do
+      attributes = {
+        cache_identifier: cache_identifier,
+        feature_category: feature_category,
+        backing_resource: backing_resource
+      }
+
+      instance = described_class.build_with_metadata(**attributes)
+
+      expect(instance).to be_a(described_class)
+      expect(instance.metadata).to have_attributes(**attributes)
+    end
+  end
+
+  describe 'Methods', :use_clean_rails_memory_store_caching do
+    let(:expected_key) { 'key' }
+
+    before do
+      allow(Gitlab::Cache::Metrics).to receive(:new).and_return(metrics_mock)
+    end
+
+    describe '#read' do
+      context 'when key does not exist' do
+        it 'returns nil' do
+          expect(client.read('key')).to be_nil
+        end
+
+        it 'increments cache miss' do
+          expect(metrics_mock).to receive(:increment_cache_miss)
+
+          client.read('key')
+        end
+      end
+
+      context 'when key exists' do
+        before do
+          backend.write(expected_key, 'value')
+        end
+
+        it 'returns key value' do
+          expect(client.read('key')).to eq('value')
+        end
+
+        it 'increments cache hit' do
+          expect(metrics_mock).to receive(:increment_cache_hit)
+
+          client.read('key')
+        end
+      end
+    end
+
+    describe '#write' do
+      it 'calls backend "#write" method with the expected key' do
+        expect(backend).to receive(:write).with(expected_key, 'value')
+
+        client.write('key', 'value')
+      end
+    end
+
+    describe '#exist?' do
+      it 'calls backend "#exist?" method with the expected key' do
+        expect(backend).to receive(:exist?).with(expected_key)
+
+        client.exist?('key')
+      end
+    end
+
+    describe '#delete' do
+      it 'calls backend "#delete" method with the expected key' do
+        expect(backend).to receive(:delete).with(expected_key)
+
+        client.delete('key')
+      end
+    end
+
+    # rubocop:disable Style/RedundantFetchBlock
+    describe '#fetch' do
+      it 'creates key in the specific format' do
+        client.fetch('key') { 'value' }
+
+        expect(backend.fetch(expected_key)).to eq('value')
+      end
+
+      it 'yields the block once' do
+        expect { |b| client.fetch('key', &b) }.to yield_control.once
+      end
+
+      context 'when key already exists' do
+        before do
+          backend.write(expected_key, 'value')
+        end
+
+        it 'does not redefine the value' do
+          expect(client.fetch('key') { 'new-value' }).to eq('value')
+        end
+
+        it 'increments a cache hit' do
+          expect(metrics_mock).to receive(:increment_cache_hit)
+
+          client.fetch('key')
+        end
+
+        it 'does not measure the cache generation time' do
+          expect(metrics_mock).not_to receive(:observe_cache_generation)
+
+          client.fetch('key') { 'new-value' }
+        end
+      end
+
+      context 'when key does not exist' do
+        it 'caches the key' do
+          expect(client.fetch('key') { 'value' }).to eq('value')
+
+          expect(client.fetch('key')).to eq('value')
+        end
+
+        it 'increments a cache miss' do
+          expect(metrics_mock).to receive(:increment_cache_miss)
+
+          client.fetch('key')
+        end
+
+        it 'measures the cache generation time' do
+          expect(metrics_mock).to receive(:observe_cache_generation)
+
+          client.fetch('key') { 'value' }
+        end
+      end
+    end
+  end
+  # rubocop:enable Style/RedundantFetchBlock
+end