implement File::Stat#size

lib/fakefs/file.rb

@@ -192,6 +192,10 @@ module FakeFS
       def nlink
         FileSystem.find(@file).links.size
       end
+
+      def size
+        File.size(@file)
+      end
     end
 
     attr_reader :path

test/file/stat_test.rb

@@ -67,4 +67,9 @@ class FileStatTest < Test::Unit::TestCase
 
     assert_equal 2, File.stat("testfile").nlink
   end
+
+  def test_file_size
+    File.open('testfile', 'w') { |f| f << 'test' }
+    assert_equal 4, File.stat('testfile').size
+  end
 end