validate_numericality_of(:amount).greater_than_or_equal_to(0)

[bitcoiners]

Hello,
Trying out remarkable with rails 3.1 app
my Gemfile
..
gem "rspec"
gem "rspec-rails"
gem "remarkable_activerecord", "~> 4.0.0.alpha4"

spec_helper
..
require 'rspec/rails'
require 'remarkable/active_record'

a model spec
..
it { should
validate_numericality_of(:amount).greater_than_or_equal_to(0) }

Get this error:

Failure/Error: it { should
validate_numericality_of(:amount).greater_than_or_equal_to(0) }
NoMethodError:
undefined method `greater_than_or_equal_to' for

RSpec::Matchers::Matcher:0xfa8e92c