Add spec for File::NULL

core/file/null_spec.rb

@@ -0,0 +1,18 @@
+require File.expand_path('../../../spec_helper', __FILE__)
+
+describe "File::NULL" do
+  ruby_version_is "1.9" do
+    platform_is :windows do
+      it "returns NUL as a string" do
+        File::NULL.should == 'NUL'
+      end
+    end
+
+    platform_is_not :windows do
+      it "returns /dev/null as a string" do
+        File::NULL.should == '/dev/null'
+      end
+    end
+  end
+end
+