test uniqueness of pair objects too!

test/models/test_pair.py

@@ -1,15 +1,31 @@
-from nose.tools import eq_
+from nose.tools import eq_, ok_
 
 from deeprank.models.pair import Pair
 
 
 def test_order_independency():
-    # test comparing:
+    # These should be the same:
     pair1 = Pair(1, 2)
     pair2 = Pair(2, 1)
+
+    # test comparing:
     eq_(pair1, pair2)
 
     # test hashing:
     d = {pair1: 1}
     d[pair2] = 2
     eq_(d[pair1], 2)
+
+
+def test_uniqueness():
+    # These should be different:
+    pair1 = Pair(1, 2)
+    pair2 = Pair(1, 3)
+
+    # test comparing:
+    ok_(pair1 != pair2)
+
+    # test hashing:
+    d = {pair1: 1}
+    d[pair2] = 2
+    eq_(d[pair1], 1)