2 files changed, 21 insertions, 6 deletions
diff --git a/activerecord/test/cases/associations/has_many_associations_test.rb b/activerecord/test/cases/associations/has_many_associations_test.rb
index 07354a2379..5ad1e2aecc 100644
--- a/activerecord/test/cases/associations/has_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_associations_test.rb
@@ -242,6 +242,13 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_equal "defaulty", bulb.name
   end
 
+  def test_build_from_association_sets_inverse_instance
+    car = Car.new(name: "honda")
+
+    bulb = car.bulbs.build
+    assert_equal car, bulb.car
+  end
+
   def test_do_not_call_callbacks_for_delete_all
     car = Car.create(name: "honda")
     car.funky_bulbs.create!
@@ -2176,6 +2183,13 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_equal "Post", tagging.taggable_type
   end
 
+  def test_build_from_polymorphic_association_sets_inverse_instance
+    post = Post.new
+    tagging = post.taggings.build
+
+    assert_equal post, tagging.taggable
+  end
+
   def test_dont_call_save_callbacks_twice_on_has_many
     firm = companies(:first_firm)
     contract = firm.contracts.create!
@@ -2545,6 +2559,11 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
 
     assert_equal [bulb.id], car.bulb_ids
     assert_no_queries { car.bulb_ids }
+
+    bulb2 = car.bulbs.create!
+
+    assert_equal [bulb.id, bulb2.id], car.bulb_ids
+    assert_no_queries { car.bulb_ids }
   end
 
   def test_loading_association_in_validate_callback_doesnt_affect_persistence
diff --git a/activerecord/test/cases/associations/inverse_associations_test.rb b/activerecord/test/cases/associations/inverse_associations_test.rb
index d8f7d3b21c..95ba6bdf8a 100644
--- a/activerecord/test/cases/associations/inverse_associations_test.rb
+++ b/activerecord/test/cases/associations/inverse_associations_test.rb
@@ -117,15 +117,11 @@ class AutomaticInverseFindingTests < ActiveRecord::TestCase
     assert !club_reflection.has_inverse?, "A has_many_through association should not find an inverse automatically"
   end
 
-  def test_polymorphic_relationships_should_still_not_have_inverses_when_non_polymorphic_relationship_has_the_same_name
+  def test_polymorphic_has_one_should_find_inverse_automatically
     man_reflection = Man.reflect_on_association(:polymorphic_face_without_inverse)
-    face_reflection = Face.reflect_on_association(:man)
-
-    assert_respond_to face_reflection, :has_inverse?
-    assert face_reflection.has_inverse?, "For this test, the non-polymorphic association must have an inverse"
 
     assert_respond_to man_reflection, :has_inverse?
-    assert !man_reflection.has_inverse?, "The target of a polymorphic association should not find an inverse automatically"
+    assert man_reflection.has_inverse?
   end
 end