Add more tests for `find_signed/!` methods
Add more tests for `find_signed/!` methods

Related to https://github.com/rails/rails/pull/39404, https://github.com/rails/rails/pull/39542

yahonda/rails,Envek/rails,yawboakye/rails,Vasfed/rails,Edouard-chin/rails,Stellenticket/rails,tgxworld/rails,rails/rails,MSP-Greg/rails,BlakeWilliams/rails,lcreid/rails,lcreid/rails,EmmaB/rails-1,tgxworld/rails,vipulnsward/rails,joonyou/rails,tgxworld/rails,joonyou/rails,yawboakye/rails,MSP-Greg/rails,kmcphillips/rails,esparta/rails,kmcphillips/rails,georgeclaghorn/rails,kddeisz/rails,eileencodes/rails,esparta/rails,yahonda/rails,Vasfed/rails,Envek/rails,rails/rails,yahonda/rails,Vasfed/rails,kmcphillips/rails,Stellenticket/rails,MSP-Greg/rails,bogdanvlviv/rails,MSP-Greg/rails,Edouard-chin/rails,tjschuck/rails,tjschuck/rails,Envek/rails,Erol/rails,lcreid/rails,vipulnsward/rails,bogdanvlviv/rails,betesh/rails,yawboakye/rails,eileencodes/rails,Edouard-chin/rails,eileencodes/rails,tjschuck/rails,tgxworld/rails,BlakeWilliams/rails,Vasfed/rails,rails/rails,joonyou/rails,betesh/rails,lcreid/rails,EmmaB/rails-1,Stellenticket/rails,betesh/rails,vipulnsward/rails,joonyou/rails,georgeclaghorn/rails,rails/rails,Envek/rails,kddeisz/rails,tjschuck/rails,yahonda/rails,Stellenticket/rails,betesh/rails,georgeclaghorn/rails,kddeisz/rails,BlakeWilliams/rails,BlakeWilliams/rails,esparta/rails,bogdanvlviv/rails,yawboakye/rails,Erol/rails,kmcphillips/rails,georgeclaghorn/rails,Erol/rails,esparta/rails,Erol/rails,bogdanvlviv/rails,EmmaB/rails-1,kddeisz/rails,Edouard-chin/rails,vipulnsward/rails,eileencodes/rails