Add Gitlab::Utils::StrongMemoize

1 files changed, 52 insertions, 0 deletions

diff --git a/spec/lib/gitlab/utils/strong_memoize_spec.rb b/spec/lib/gitlab/utils/strong_memoize_spec.rb
new file mode 100644
index 00000000000..4a104ab6d97
--- /dev/null
+++ b/spec/lib/gitlab/utils/strong_memoize_spec.rb
@@ -0,0 +1,52 @@
+require 'spec_helper'
+
+describe Gitlab::Utils::StrongMemoize do
+  let(:klass) do
+    struct = Struct.new(:value) do
+      def method_name
+        strong_memoize(:method_name) do
+          trace << value
+          value
+        end
+      end
+
+      def trace
+        @trace ||= []
+      end
+    end
+
+    struct.include(described_class)
+    struct
+  end
+
+  subject(:object) { klass.new(value) }
+
+  shared_examples 'caching the value' do
+    it 'only calls the block once' do
+      value0 = object.method_name
+      value1 = object.method_name
+
+      expect(value0).to eq(value)
+      expect(value1).to eq(value)
+      expect(object.trace).to contain_exactly(value)
+    end
+
+    it 'returns and defines the instance variable for the exact value' do
+      returned_value = object.method_name
+      memoized_value = object.instance_variable_get(:@method_name)
+
+      expect(returned_value).to eql(value)
+      expect(memoized_value).to eql(value)
+    end
+  end
+
+  describe '#strong_memoize' do
+    [nil, false, true, 'value', 0, [0]].each do |value|
+      context "with value #{value}" do
+        let(:value) { value }
+
+        it_behaves_like 'caching the value'
+      end
+    end
+  end
+end