diff --git a/app/models/test_pair.rb b/app/models/test_pair.rb
--- a/app/models/test_pair.rb
+++ b/app/models/test_pair.rb
@@ -5,4 +5,29 @@
     return TestPair.where(:problem_id => problem.id,
                           :is_private => is_private).first
   end
+
+  def grade(output)
+    out_items = output.split("\n")
+    sol_items = solution.split("\n")
+    res = ''
+    f = 0
+    s = 0
+    sol_items.length.times do |i|
+      f += 1
+      si = sol_items[i].chomp
+      if out_items[i]
+        oi = out_items[i].chomp
+      else
+        oi = ''
+      end
+      if oi == si
+        res = res + 'P'
+        s += 1
+      else
+        res = res + '-'
+      end
+    end
+    return { :score => s, :full_score => f, :msg => res }
+  end
+
 end