2 files changed, 14 insertions, 4 deletions
diff --git a/activerecord/test/cases/associations/belongs_to_associations_test.rb b/activerecord/test/cases/associations/belongs_to_associations_test.rb
index 938350627f..4f99c57c3c 100644
--- a/activerecord/test/cases/associations/belongs_to_associations_test.rb
+++ b/activerecord/test/cases/associations/belongs_to_associations_test.rb
@@ -53,7 +53,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
 
   def test_belongs_to_with_primary_key_joins_on_correct_column
     sql = Client.joins(:firm_with_primary_key).to_sql
-    if current_adapter?(:MysqlAdapter, :Mysql2Adapter)
+    if current_adapter?(:Mysql2Adapter)
       assert_no_match(/`firm_with_primary_keys_companies`\.`id`/, sql)
       assert_match(/`firm_with_primary_keys_companies`\.`name`/, sql)
     elsif current_adapter?(:OracleAdapter)
diff --git a/activerecord/test/cases/associations/eager_test.rb b/activerecord/test/cases/associations/eager_test.rb
index 622c984b3b..966789884b 100644
--- a/activerecord/test/cases/associations/eager_test.rb
+++ b/activerecord/test/cases/associations/eager_test.rb
@@ -1247,11 +1247,15 @@ class EagerAssociationTest < ActiveRecord::TestCase
       subclass = Class.new(ActiveRecord::Base) do
         def self.name; "Author"; end
         self.table_name = "authors"
-        has_many :posts_ordered_by_comments_tags_count, -> { joins('LEFT JOIN comments ON comments.post_id = posts.id').order("SUM(comments.tags_count)").group('posts.id') }, :class_name => "Post"
+        has_many :posts_ordered_by_comments_tags_count, -> {
+          joins('LEFT JOIN comments ON comments.post_id = posts.id').
+          order("SUM(comments.tags_count)").
+          group('posts.id') }, class_name: "Post"
       end
 
-      posts = subclass.includes(:posts_ordered_by_comments_tags_count).first.posts_ordered_by_comments_tags_count
-      assert_equal subclass.first.posts_ordered_by_comments_tags_count, posts
+      preloaded = subclass.includes(:posts_ordered_by_comments_tags_count).map(&:posts_ordered_by_comments_tags_count)
+      loaded = subclass.all.map(&:posts_ordered_by_comments_tags_count)
+      assert preloaded == loaded, 'Preloaded records differ from expected result.'
     end
   end
 
@@ -1415,4 +1419,10 @@ class EagerAssociationTest < ActiveRecord::TestCase
     post = Post.eager_load(:tags).where('tags.name = ?', 'General').first
     assert_equal posts(:welcome), post
   end
+
+  # CollectionProxy#reader is expensive, so the preloader avoids calling it.
+  test "preloading has_many_through association avoids calling association.reader" do
+    ActiveRecord::Associations::HasManyAssociation.any_instance.expects(:reader).never
+    Author.preload(:readonly_comments).first!
+  end
 end