RSpec matcher to test mass assignment

gistfile1.rb

RSpec::Matchers.define :allow_assignment_for do |attribute|
  @attribute = attribute

  match_for_should do |record|
    @record = record
    matches_against?(true)
  end

  match_for_should_not do |record|
    @record = record
    matches_against?(false)
  end

  def matches_against?(compare)
    raise "The allow_assignment_for matcher requires an attribute; use subject.should allow_assignment_for(attribute)" unless @attribute
    
    @record.class.accessible_attributes.include?(@attribute.to_sym) == compare
  end

  failure_message_for_should do |actual|
    "expect to allow mass assignment for #{@attribute.inspect}"
  end

  failure_message_for_should_not do |actual|
    "expect to reject mass assignment for #{@attribute.inspect}"
  end

  description do
    "allow assignment for #{@attribute.inspect}"
  end
end