1 files changed, 26 insertions, 0 deletions
diff --git a/activerecord/test/cases/associations/deprecated_counter_cache_on_has_many_through_test.rb b/activerecord/test/cases/associations/deprecated_counter_cache_on_has_many_through_test.rb
new file mode 100644
index 0000000000..48f7ddbe83
--- /dev/null
+++ b/activerecord/test/cases/associations/deprecated_counter_cache_on_has_many_through_test.rb
@@ -0,0 +1,26 @@
+require "cases/helper"
+
+class DeprecatedCounterCacheOnHasManyThroughTest < ActiveRecord::TestCase
+  class Post < ActiveRecord::Base
+    has_many :taggings, as: :taggable
+    has_many :tags, through: :taggings
+  end
+
+  class Tagging < ActiveRecord::Base
+    belongs_to :taggable, polymorphic: true
+    belongs_to :tag
+  end
+
+  class Tag < ActiveRecord::Base
+  end
+
+  test "counter caches are updated in the database if the belongs_to association doesn't specify a counter cache" do
+    post = Post.create!(title: 'Hello', body: 'World!')
+    assert_deprecated { post.tags << Tag.create!(name: 'whatever') }
+
+    assert_equal 1, post.tags.size
+    assert_equal 1, post.tags_count
+    assert_equal 1, post.reload.tags.size
+    assert_equal 1, post.reload.tags_count
+  end
+end