class RSpec::Rails::Matchers::BeANew

end
assigns(:thing).should be_a_new(Thing).with(:name => nil)
post :create, :thing => { :name => "Illegal Value" }
it "assigns a new Thing with the submitted attributes" do

@example

Use this to specify the specific attributes to match on the new record.

def with(expected_attributes)
  attributes.merge!(expected_attributes)
  self
end