Add support for testing undefined resource parameters

Closes #13

README.md

@@ -78,6 +78,13 @@ the generic `with_<parameter>` chains.
 it { should contain_package('mysql-server').with_ensure('present') }
 ```
 
+You can also test that specific parameters have been left undefined with the
+generic `without_<parameter>` chains.
+
+```ruby
+it { should contain_file('/foo/bar').without_mode }
+```
+
 ## Writing tests
 
 ### Basic test structure

lib/rspec-puppet/matchers/create_generic.rb

@@ -14,6 +14,10 @@ module RSpec::Puppet
           param = method.to_s.gsub(/^with_/, '')
           (@expected_params ||= []) << [param, args[0]]
           self
+        elsif method.to_s =~ /^without_/
+          param = method.to_s.gsub(/^without_/, '')
+          (@expected_undef_params ||= []) << param
+          self
         else
           super
         end
@@ -34,6 +38,15 @@ module RSpec::Puppet
               end
             end
           end
+
+          if @expected_undef_params
+            @expected_undef_params.each do |name|
+              unless resource.send(:parameters)[name.to_sym].nil?
+                ret = false
+                (@errors ||= []) << "#{name.to_s} undefined"
+              end
+            end
+          end
         end
 
         ret

spec/defines/sysctl_spec.rb

@@ -9,5 +9,6 @@ describe 'sysctl' do
     .with_context('/files/etc/sysctl.conf') \
     .with_changes("set vm.swappiness '60'") \
     .with_onlyif("match vm.swappiness[.='60'] size == 0") \
-    .with_notify('Exec[sysctl/reload]') }
+    .with_notify('Exec[sysctl/reload]')\
+    .without_foo }
 end