Toying around with an RSpec DSL for permutations. My real use case is more complex than this example - the large numbers of inputs and outputs makes it more concise to "demonstrate" correctness and expectations than to "spec" it out with traditional, one

address_spec.rb

describe Address do
  permute "validations" do
    cases [
      [:address,      :address_2,   :city,            :state,   :zip,     :country,   :valid,   :errors_on],
      [ nil,          nil,          nil,              nil,      nil,      nil,        false,    ['address', 'city', 'state', 'zip', 'country']],
      ['123 Main St', 'Apt 100',    'Pleasantville',  'NC',     '12345',  'US',       true,     []],
      ['123 Main St'  'Apt 100',    'Pleasantville'   'NC'      '12345'   nil,        false     ['country']]
      ['123 Main St'  'Apt 100',    'Pleasantville'   'NC'      '12345'   'U',        false     ['country']]
      ['123 Main St'  'Apt 100',    'Pleasantville'   'NC'      '12345'   'USA',      false     ['country']]
    ]
    
    before do
      @address = Address.new(
        :address => d[:address],
        :address_2 => d[:address_2],
        :city => d[:city],
        :state => d[:state],
        :zip => d[:zip]
      )
    end
    
    it "reports correctly for valid?" do
      @address.valid?.should == d[:valid]
    end
    
    it "has errors on the correct attributes" do
      @address.valid?
      @address.errors.keys.sort.should == d[:errors_on].sort
    end
    
    conditionally_on(d[:country].blank?) do
      it "has only 1 error on 'country', for being blank" do
        @address.errors.get(:country).should == "can't be blank"
      end
    end
    
    conditionally_on(d[:country].size != 2) do
      it "has only 1 error on 'country', for not being 2 characters" do
        @address.errors.get(:country).should == "must be a valid 2-character country code"
      end
    end
  end
end

# Address validations case 1 (:address => nil, :address_2 => nil, ...) reports correctly for valid?
# Address validations case 1 (:address => nil, :address_2 => nil, ...) has errors on the correct attributes
#
# Address validations case 2 (:address => '123 Main St', :address_2 => 'Apt 100', ...) reports correctly for valid?
# Address validations case 2 (:address => '123 Main St', :address_2 => 'Apt 100', ...) has errors on the correct attributes
#
# Address validations case 3 (:address => '123 Main St', :address_2 => 'Apt 100', ...) reports correctly for valid?
# Address validations case 3 (:address => '123 Main St', :address_2 => 'Apt 100', ...) has errors on the correct attributes
# Address validations case 3 (:address => '123 Main St', :address_2 => 'Apt 100', ...) has only 1 error on 'country', for being blank
#
# Address validations case 4 (:address => '123 Main St', :address_2 => 'Apt 100', ...) reports correctly for valid?
# Address validations case 4 (:address => '123 Main St', :address_2 => 'Apt 100', ...) has errors on the correct attributes
# Address validations case 4 (:address => '123 Main St', :address_2 => 'Apt 100', ...) has only 1 error on 'country', for not being 2 characters
#
# Address validations case 5 (:address => '123 Main St', :address_2 => 'Apt 100', ...) reports correctly for valid?
# Address validations case 5 (:address => '123 Main St', :address_2 => 'Apt 100', ...) has errors on the correct attributes
# Address validations case 5 (:address => '123 Main St', :address_2 => 'Apt 100', ...) has only 1 error on 'country', for not being 2 characters