【RSpecエラー】validate_uniqueness_ofを使うとテストが通らないとき

環境

Ruby 3.0.2
Rails 6.1.4.1

状況

バリデーションのテスト実行時に下記のエラー
デフォルトでは大文字と小文字を区別している

model.rb

validates :email, uniqueness: true

spec.rb

it { is_expected.to validate_uniqueness_of(:email) }

Expected Employee to validate that :email is case-sensitively unique,
       but this could not be proved.
         After taking the given Employee, setting its :email to ‹"dummy
         value"›, and saving it as the existing record, then making a new
         Employee and setting its :email to a different value, ‹"DUMMY VALUE"›,
         the matcher expected the new Employee to be valid, but it was invalid
         instead, producing these validation errors:

解決法

大文字小文字の区別なくテストするignoring_case_sensitivityメソッドを追加

spec.rb

it { is_expected.to validate_uniqueness_of(:email).ignoring_case_sensitivity }

参考