Fix typo and add sanity test for code statistics rake task.

Signed-off-by: NJosé Valim <jose.valim@gmail.com>

railties/lib/rails/code_statistics.rb

@@ -23,7 +23,7 @@ def to_s
 
   private
     def calculate_statistics
-      Hash[@pais.map { |pair| [pair.first, calculate_directory_statistics(pair.last)] }]
+      Hash[@pairs.map{|pair| [pair.first, calculate_directory_statistics(pair.last)]}]
     end
 
     def calculate_directory_statistics(directory, pattern = /.*\.rb$/)

railties/test/application/rake_test.rb

@@ -33,5 +33,10 @@ def test_environment_is_required_in_rake_tasks
 
       assert_match "SuperMiddleware", Dir.chdir(app_path){ `rake middleware` }
     end
+
+    def test_code_statistics_sanity
+      assert_match "Code LOC: 5     Test LOC: 0     Code to Test Ratio: 1:0.0",
+        Dir.chdir(app_path){ `rake stats` }
+    end
   end
-end
\ No newline at end of file
+end