Add test for `AR::Base#to_param`

According to the doc of `AR::Base#to_param`(
https://github.com/rails/rails/blob/04cda1848cb847c2bdad0bfc12160dc8d554
7775/activerecord/lib/active_record/integration.rb#L18 ), it returns
`nil` if the record is not persisted.

1 files changed, 6 insertions, 1 deletions

diff --git a/activerecord/test/cases/integration_test.rb b/activerecord/test/cases/integration_test.rb
index 7fbde4e2f9..b0a7cda2f3 100644
--- a/activerecord/test/cases/integration_test.rb
+++ b/activerecord/test/cases/integration_test.rb
@@ -11,7 +11,12 @@ class IntegrationTest < ActiveRecord::TestCase
     assert_kind_of String, Client.first.to_param
   end
 
-  def test_to_param_returns_id_even_if_not_persisted
+  def test_to_param_returns_nil_if_not_persisted
+    client = Client.new
+    assert_equal nil, client.to_param
+  end
+
+  def test_to_param_returns_id_if_not_persisted_but_id_is_set
     client = Client.new
     client.id = 1
     assert_equal '1', client.to_param