1 files changed, 133 insertions, 0 deletions
diff --git a/spec/lib/gitlab/cache/request_cache_spec.rb b/spec/lib/gitlab/cache/request_cache_spec.rb
new file mode 100644
index 00000000000..5b82c216a13
--- /dev/null
+++ b/spec/lib/gitlab/cache/request_cache_spec.rb
@@ -0,0 +1,133 @@
+require 'spec_helper'
+
+describe Gitlab::Cache::RequestCache do
+  let(:klass) do
+    Class.new do
+      extend Gitlab::Cache::RequestCache
+
+      attr_accessor :id, :name, :result, :extra
+
+      def self.name
+        'ExpensiveAlgorithm'
+      end
+
+      def initialize(id, name, result, extra = nil)
+        self.id = id
+        self.name = name
+        self.result = result
+        self.extra = nil
+      end
+
+      request_cache def compute(arg)
+        result << arg
+      end
+
+      request_cache def repute(arg)
+        result << arg
+      end
+
+      def dispute(arg)
+        result << arg
+      end
+      request_cache(:dispute) { extra }
+    end
+  end
+
+  let(:algorithm) { klass.new('id', 'name', []) }
+
+  shared_examples 'cache for the same instance' do
+    it 'does not compute twice for the same argument' do
+      algorithm.compute(true)
+      result = algorithm.compute(true)
+
+      expect(result).to eq([true])
+    end
+
+    it 'computes twice for the different argument' do
+      algorithm.compute(true)
+      result = algorithm.compute(false)
+
+      expect(result).to eq([true, false])
+    end
+
+    it 'computes twice for the different class name' do
+      algorithm.compute(true)
+      allow(klass).to receive(:name).and_return('CheapAlgo')
+      result = algorithm.compute(true)
+
+      expect(result).to eq([true, true])
+    end
+
+    it 'computes twice for the different method' do
+      algorithm.compute(true)
+      result = algorithm.repute(true)
+
+      expect(result).to eq([true, true])
+    end
+
+    context 'when request_cache_key is provided' do
+      before do
+        klass.request_cache_key do
+          [id, name]
+        end
+      end
+
+      it 'computes twice for the different keys, id' do
+        algorithm.compute(true)
+        algorithm.id = 'ad'
+        result = algorithm.compute(true)
+
+        expect(result).to eq([true, true])
+      end
+
+      it 'computes twice for the different keys, name' do
+        algorithm.compute(true)
+        algorithm.name = 'same'
+        result = algorithm.compute(true)
+
+        expect(result).to eq([true, true])
+      end
+
+      it 'uses extra method cache key if provided' do
+        algorithm.dispute(true) # miss
+        algorithm.extra = true
+        algorithm.dispute(true) # miss
+        result = algorithm.dispute(true) # hit
+
+        expect(result).to eq([true, true])
+      end
+    end
+  end
+
+  context 'when RequestStore is active', :request_store do
+    it_behaves_like 'cache for the same instance'
+
+    it 'computes once for different instances when keys are the same' do
+      algorithm.compute(true)
+      result = klass.new('id', 'name', algorithm.result).compute(true)
+
+      expect(result).to eq([true])
+    end
+
+    it 'computes twice if RequestStore starts over' do
+      algorithm.compute(true)
+      RequestStore.end!
+      RequestStore.clear!
+      RequestStore.begin!
+      result = algorithm.compute(true)
+
+      expect(result).to eq([true, true])
+    end
+  end
+
+  context 'when RequestStore is inactive' do
+    it_behaves_like 'cache for the same instance'
+
+    it 'computes twice for different instances even if keys are the same' do
+      algorithm.compute(true)
+      result = klass.new('id', 'name', algorithm.result).compute(true)
+
+      expect(result).to eq([true, true])
+    end
+  end
+end