diff --git a/app/models/test_pair_assignment.rb b/app/models/test_pair_assignment.rb
new file mode 100644
--- /dev/null
+++ b/app/models/test_pair_assignment.rb
@@ -0,0 +1,9 @@
+class TestPairAssignment < ActiveRecord::Base
+  belongs_to :problem
+  belongs_to :test_pair
+  belongs_to :user
+
+  def expired?
+    return created_at + TEST_ASSIGNMENT_EXPIRATION_DURATION < Time.new.gmtime 
+  end
+end