Added specs for Numeric#dup

Author: andrykonchin

core/numeric/dup_spec.rb

@@ -0,0 +1,16 @@
+require_relative '../../spec_helper'
+
+describe "Numeric#dup" do
+  it "returns self" do
+    value = 1
+    value.dup.should equal(value)
+
+    subclass = Class.new(Numeric)
+    value = subclass.new
+    value.dup.should equal(value)
+  end
+
+  it "does not change frozen status" do
+    1.dup.frozen?.should == true
+  end
+end