Ensure #second acts like #first AR finder

This commit bring the famous ordinal Array instance methods defined
in ActiveSupport into ActiveRecord as fully-fledged finders.

These finders ensure a default ascending order of the table's primary
key, and utilize the OFFSET SQL verb to locate the user's desired
record. If an offset is defined in the query, calling #second adds
to the offset to get the actual desired record.

Fixes #13743.

1 files changed, 89 insertions, 1 deletions

diff --git a/activerecord/test/cases/finder_test.rb b/activerecord/test/cases/finder_test.rb
index 9b575557de..9cd1e0ace8 100644
--- a/activerecord/test/cases/finder_test.rb
+++ b/activerecord/test/cases/finder_test.rb
@@ -254,6 +254,94 @@ class FinderTest < ActiveRecord::TestCase
     end
   end
 
+  def test_second
+    assert_equal topics(:second).title, Topic.second.title
+  end
+
+  def test_second_with_offset
+    assert_equal topics(:fifth), Topic.offset(3).second
+  end
+
+  def test_second_have_primary_key_order_by_default
+    expected = topics(:second)
+    expected.touch # PostgreSQL changes the default order if no order clause is used
+    assert_equal expected, Topic.second
+  end
+
+  def test_model_class_responds_to_second_bang
+    assert Topic.second!
+    Topic.delete_all
+    assert_raises ActiveRecord::RecordNotFound do
+      Topic.second!
+    end
+  end
+
+  def test_third
+    assert_equal topics(:third).title, Topic.third.title
+  end
+
+  def test_third_with_offset
+    assert_equal topics(:fifth), Topic.offset(2).third
+  end
+
+  def test_third_have_primary_key_order_by_default
+    expected = topics(:third)
+    expected.touch # PostgreSQL changes the default order if no order clause is used
+    assert_equal expected, Topic.third
+  end
+
+  def test_model_class_responds_to_third_bang
+    assert Topic.third!
+    Topic.delete_all
+    assert_raises ActiveRecord::RecordNotFound do
+      Topic.third!
+    end
+  end
+
+  def test_fourth
+    assert_equal topics(:fourth).title, Topic.fourth.title
+  end
+
+  def test_fourth_with_offset
+    assert_equal topics(:fifth), Topic.offset(1).fourth
+  end
+
+  def test_fourth_have_primary_key_order_by_default
+    expected = topics(:fourth)
+    expected.touch # PostgreSQL changes the default order if no order clause is used
+    assert_equal expected, Topic.fourth
+  end
+
+  def test_model_class_responds_to_fourth_bang
+    assert Topic.fourth!
+    Topic.delete_all
+    assert_raises ActiveRecord::RecordNotFound do
+      Topic.fourth!
+    end
+  end
+
+  def test_fifth
+    assert_equal topics(:fifth).title, Topic.fifth.title
+  end
+
+  def test_fifth_with_offset
+    assert_equal topics(:fifth), Topic.offset(0).fifth
+  end
+
+  def test_fifth_have_primary_key_order_by_default
+    expected = topics(:fifth)
+    expected.touch # PostgreSQL changes the default order if no order clause is used
+    assert_equal expected, Topic.fifth
+  end
+
+  def test_model_class_responds_to_fifth_bang
+    assert Topic.fifth!
+    Topic.delete_all
+    assert_raises ActiveRecord::RecordNotFound do
+      Topic.fifth!
+    end
+  end
+
   def test_last_bang_present
     assert_nothing_raised do
       assert_equal topics(:second), Topic.where("title = 'The Second Topic of the day'").last!
@@ -267,7 +355,7 @@ class FinderTest < ActiveRecord::TestCase
   end
 
   def test_model_class_responds_to_last_bang
-    assert_equal topics(:fourth), Topic.last!
+    assert_equal topics(:fifth), Topic.last!
     assert_raises ActiveRecord::RecordNotFound do
       Topic.delete_all
       Topic.last!