fix checking whether client id is in experiment (#181)

taar/recommenders/randomizer.py

@@ -15,7 +15,7 @@ def in_experiment(client_id, xp_prob=0.5):
     """
     hex_client = "".join([c for c in client_id.lower() if c in "abcdef0123456789"])
     int_client = int(hex_client, 16)
-    return int((int_client % 100) <= (xp_prob * 100))
+    return int((int_client % 100) < (xp_prob * 100))
 
 
 def reorder_guids(guid_weight_tuples, size=None):

tests/test_randomizer.py

@@ -59,3 +59,10 @@ def test_experimental_branch_guid():
 
         total = sum([in_experiment(id, cutoff - 0.1) for i in range(100)])
         assert total == 0
+
+
+def test_in_experiment_zero_prob():
+    """
+    Test the edge case when some client IDs go to experiment even with 0 probability.
+    """
+    assert not in_experiment('0ace1ca2a3519332ab93e76a049fe74091fa8fc9063399caa8545dd23f93de5c', xp_prob=0.0)