Add test case for `collection.size` with dirty target

1 files changed, 10 insertions, 0 deletions

diff --git a/activerecord/test/cases/associations/has_many_associations_test.rb b/activerecord/test/cases/associations/has_many_associations_test.rb
index b00a3880f6..33fe5ccabc 100644
--- a/activerecord/test/cases/associations/has_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_associations_test.rb
@@ -983,6 +983,16 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_not_empty company.contracts
   end
 
+  def test_collection_size_with_dirty_target
+    post = posts(:thinking)
+    assert_equal [], post.reader_ids
+    assert_equal 0, post.readers.size
+    post.readers.reset
+    post.readers.build
+    assert_equal [], post.reader_ids
+    assert_equal 1, post.readers.size
+  end
+
   def test_collection_size_twice_for_regressions
     post = posts(:thinking)
     assert_equal 0, post.readers.size