@mcmire, Thank you for the comment. 
Looks like the code above doesn't work because fail_with_message matcher uses '==' instead of 'include'.

This works, but probably we would not use the number '1' when writing the test code first.

```ruby
expect {
  define_model(:example, :attr => :string).new.should match
}.to fail_with_message('Expected errors to include "must be even" when attr is set to 1, got no errors')
``` 

So far these are what I'm thinking of:
- 1. Use fail_with_message as above
- 2. Keep the previous code which uses "include"
- 3. Create a new matcher 'fail_with_message_including'

What would you say? I'm sorry if I'm missing something. :p