The Best Way to Test the Validations on Models in ActiveRecord

user.rb

class User < ActiveRecord::Base

  validates :username, presence: :true
  validates :password_digest, presence: :true

  has_secure_password

end

user_test.rb

test "the user's valitations" do
    assert @user._validators[:username].any? do |validator|
      validator.is_kind_of? ActiveRecord::Validations::PresenceValidator
    end

    assert @user._validators[:password].any? do |validator|
      validator.is_kind_of? ActiveRecord::Validations::PresenceValidator
    end

    assert @user._validators[:password].any? do |validator|
      validator.is_kind_of? ActiveRecord::Validations::LengthValidator
    end
end

test "the number of user's valitations" do
    assert_equal 3, @user._validators.count
end

Take a look at shoulda-matchers and in the validates_presence_of matcher =)

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