Add spec for File.socket?

spec/ruby/core/file/socket_spec.rb

@@ -1,10 +1,31 @@
 require File.expand_path('../../../spec_helper', __FILE__)
 require File.expand_path('../../../shared/file/socket', __FILE__)
+require 'socket'
 
 describe "File.socket?" do
   it_behaves_like :file_socket, :socket?, File
 end
 
 describe "File.socket?" do
-  it "needs to be reviewed for spec completeness"
+  it "returns false if file does not exist" do
+    File.socket?("I_am_a_bogus_file").should == false
+  end
+
+  it "returns false if the file is not a socket" do
+    filename = tmp("i_exist")
+    touch(filename)
+
+    File.socket?(filename).should == false
+
+    rm_r filename
+  end
+
+  it "returns true if the file is a socket" do
+    filename = tmp("i_am_a_socket")
+    server = UNIXServer.new filename
+
+    File.socket?(filename).should == true
+
+    rm_r filename
+  end
 end