ruby on rails - Difference between expect and is_expected.to in Rspec -

what difference between keywords.

in following example, using expect passed test, while is_expected.to failed it.

it { expect validate_uniqueness_of(:access_token) }

it { is_expected.to validate_uniqueness_of(:access_token) }

testing class user, generated devise

class user < activerecord::base   devise :lockable, :database_authenticatable, :registerable, :recoverable, :rememberable, :trackable, :validatable    validates :access_token, uniqueness: true    before_validation :generate_access_token!, on: :create    def generate_access_token!     begin       self.access_token = devise.friendly_token     end while user.find_by(access_token: self.access_token)   end end 

is_expected_to shorter version of writing

expect(subject).to 

your first spec passes because not testing @ all.

the second spec fails because there no uniqueness validation. although code handling duplicates (but same race condition validation), doing in different way: generates new token, rather reporting error. validation matchers typically work checking object's errors hash, , code doesn't set spec fails.