Add specs for Set initialization behavior

Author: ivoanjo

spec/concurrent/set_spec.rb

@@ -3,6 +3,44 @@ module Concurrent
   RSpec.describe Set do
     let!(:set) { described_class.new }
 
+    describe '.[]' do
+      describe 'when initializing with no arguments' do
+        it do
+          expect(described_class[]).to be_empty
+        end
+      end
+
+      describe 'when initializing with arguments' do
+        it 'creates a set with the given objects' do
+          expect(described_class[:hello, :world]).to eq ::Set.new([:hello, :world])
+        end
+      end
+    end
+
+    describe '.new' do
+      describe 'when initializing with no arguments' do
+        it do
+          expect(described_class.new).to be_empty
+        end
+      end
+
+      describe 'when initializing with an enumerable object' do
+        let(:enumerable_object) { [:hello, :world] }
+
+        it 'creates a set with the contents of the enumerable object' do
+          expect(described_class.new(enumerable_object)).to eq ::Set.new([:hello, :world])
+        end
+
+        describe 'when initializing with a block argument' do
+          let(:block_argument) { proc { |value| :"#{value}_ruby" } }
+
+          it 'creates a set with the contents of the enumerable object' do
+            expect(described_class.new(enumerable_object, &block_argument)).to eq ::Set.new([:hello_ruby, :world_ruby])
+          end
+        end
+      end
+    end
+
     context 'concurrency' do
       it do
         (1..Concurrent::ThreadSafe::Test::THREADS).map do |i|