A formatter for Wrong that displays full error messages when an ActiveRecord instance is invalid

gistfile1.rb

# Can be placed in with your test helpers. Eventually I'm hoping to package as a gem
module Wrong
  class ActiveRecordErrors < FailureMessage::Formatter
    register
    
    def match?
      predicate.is_a?(Predicated::Call) &&
        object_is_an_active_record?(predicate.left) &&
        method_runs_validations?(predicate.method_sym) &&
        failed_because_of_validations?(predicate.left)
    end
    
    def describe
      " the record is invalid:\n" + predicate.left.errors.full_messages.map {|fm| "\t* #{fm}"}.join("\n")
    end
    
    private
    def object_is_an_active_record?(object)
      object.is_a?(ActiveRecord::Base)
    end
    
    METHODS = [:valid?, :save!, :save, :create!, :create]
    def method_runs_validations?(method)
      METHODS.include?(method)
    end
    
    def failed_because_of_validations?(object)
      !object.valid?
    end
  end
end