rspec/rspec-rails — pull request #649 by tubbo (2012-12-06 02:00:29+00:00)
Title: When `expect(foo).to be_valid` fails, the validation errors are listed in the default failure message

Resolves #645 by adding a new matcher, `BeValid`, to `RSpec::Rails::Matchers`, that runs the `valid?` call on a given class that includes `ActiveModel::Validations`. If there are any validation errors, it prints said errors in the default failure message.