Added Gitlab::Lazy

This class can be used to lazy-evaluate blocks of code the first time
they're called. This can be useful when a method performs a certain
heavy operation (e.g. a SQL query) that you only want to perform
whenever the result is used for the first time.

1 files changed, 37 insertions, 0 deletions

diff --git a/spec/lib/gitlab/lazy_spec.rb b/spec/lib/gitlab/lazy_spec.rb
new file mode 100644
index 00000000000..b5ca89dd242
--- /dev/null
+++ b/spec/lib/gitlab/lazy_spec.rb
@@ -0,0 +1,37 @@
+require 'spec_helper'
+
+describe Gitlab::Lazy, lib: true do
+  let(:dummy) { double(:dummy) }
+
+  context 'when not calling any methods' do
+    it 'does not call the supplied block' do
+      expect(dummy).not_to receive(:foo)
+
+      described_class.new { dummy.foo }
+    end
+  end
+
+  context 'when calling a method on the object' do
+    it 'lazy loads the value returned by the block' do
+      expect(dummy).to receive(:foo).and_return('foo')
+
+      lazy = described_class.new { dummy.foo }
+
+      expect(lazy.to_s).to eq('foo')
+    end
+  end
+
+  describe '#respond_to?' do
+    it 'returns true for a method defined on the wrapped object' do
+      lazy = described_class.new { 'foo' }
+
+      expect(lazy).to respond_to(:downcase)
+    end
+
+    it 'returns false for a method not defined on the wrapped object' do
+      lazy = described_class.new { 'foo' }
+
+      expect(lazy).not_to respond_to(:quack)
+    end
+  end
+end