RSpec matcher to test validations and error messages

gistfile1

RSpec::Matchers.define :have_errors_on do |attribute, *values|
 
  @attribute = attribute
  @values    = values
  @failed    = []
  
  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)
     @values.each do |value|
       @record.__send__("#{@attribute}=", value)
       @record.valid?
       
       @failed << value if @record.errors[@attribute].empty? == compare
     end
    
     if @message
       @failed.empty? && @record.errors[@attribute].include?(@message)
     else
       @failed.empty?
     end    
  end 
  
  failure_message_for_should do |model|
    if @message
      "expected #{@record.inspect} to have #{@message.inspect} error message for each of #{@values.inspect} on #{@attribute.inspect} (didn't accept #{@failed.inspect})"
    else
      "expected #{@record.inspect} to have errors for each of #{@values.inspect} on #{@attribute.inspect} (didn't accept #{@failed.inspect})"
    end
  end
  
  failure_message_for_should_not do |model|
    "expected #{@record.inspect} to haven't errors for each of#{@values.inspect} on #{@attribute.inspect} (accepted #{@failed.inspect})"
  end
  
  chain :with_message do |message|
    @message = message
  end
  
  description do
    if @message
      "have errors for #{values.inspect} on #{@attribute} with message #{@message.inspect}"
    else
      "have errors for #{values.inspect} on #{@attribute}"
    end
  end
end