The Queue constructor should take an initial set of objects

Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>

core/queue/initialize_spec.rb

@@ -0,0 +1,44 @@
+require_relative '../../spec_helper'
+
+describe "Queue#initialize" do
+  it "can be passed no arguments for an empty Queue" do
+    q = Queue.new
+    q.size.should == 0
+    q.should.empty?
+  end
+
+  ruby_version_is '3.1' do
+    it "adds all elements of the passed Enumerable to self" do
+      q = Queue.new([1, 2, 3])
+      q.size.should == 3
+      q.should_not.empty?
+      q.pop.should == 1
+      q.pop.should == 2
+      q.pop.should == 3
+      q.should.empty?
+    end
+
+    it "uses #to_ary on the provided Enumerable" do
+      enumerable = MockObject.new('mock-enumerable')
+      enumerable.should_receive(:to_ary).and_return([1, 2, 3])
+      q = Queue.new(enumerable)
+      q.size.should == 3
+      q.should_not.empty?
+      q.pop.should == 1
+      q.pop.should == 2
+      q.pop.should == 3
+      q.should.empty?
+    end
+
+    it "raises if the provided Enumerable does not respond to #to_ary" do
+      enumerable = MockObject.new('mock-enumerable')
+      -> { Queue.new(enumerable) }.should raise_error(TypeError, "no implicit conversion of MockObject into Array")
+    end
+
+    it "raises if the provided Enumerable #to_ary does not return an Array" do
+      enumerable = MockObject.new('mock-enumerable')
+      enumerable.should_receive(:to_ary).and_return(14)
+      -> { Queue.new(enumerable) }.should raise_error(TypeError, "can't convert MockObject to Array (MockObject#to_ary gives Integer)")
+    end
+  end
+end