class Shoulda::ActiveRecord::Matchers::HaveDbColumnMatcher

def correct_null?
  return true if @null.nil?
  if matched_column.null.to_s == @null.to_s
    true
  else
    @missing = "#{model_class} has a db column named #{@column} " <<
               "of null #{matched_column.null}, " <<
               "not #{@null}."
    false
  end
end