Fixed #3171 Applied offer on min num of basket and benefit items

src/oscar/apps/basket/utils.py

 
             # respect max_affected_items
             if offer.benefit.max_affected_items:
-                max_affected_items = offer.benefit.max_affected_items
+                max_affected_items = min(offer.benefit.max_affected_items, max_affected_items)
 
         return max_affected_items - self.consumed(offer)

tests/integration/basket/test_utils.py

 
 import pytest
 
+from oscar.apps.offer import models
 from oscar.apps.offer.applicator import Applicator
 from oscar.test.factories import (
     BasketFactory, ConditionalOfferFactory, ProductFactory)
         for line in filled_basket.all_lines():
             assert line.consumer.consumed() == 0
 
+    def test_available_with_offer(self):
+        basket = BasketFactory()
+        product1 = ProductFactory()
+        product2 = ProductFactory()
+        basket.add_product(product1, quantity=1)
+        basket.add_product(product2, quantity=10)
+
+        benefit = models.Benefit(
+            type=models.Benefit.PERCENTAGE,
+            value=10,
+            max_affected_items=5,
+        )
+        benefit.save()
+
+        offer1 = ConditionalOfferFactory(name='offer1', benefit=benefit)
+        lines = basket.all_lines()
+        assert lines[0].consumer.available(offer1) == 1
+        assert lines[1].consumer.available(offer1) == 5
+
     def test_consumed_with_offer(self, filled_basket):
         offer1 = ConditionalOfferFactory(name='offer1')
         offer2 = ConditionalOfferFactory(name='offer2')