Support parameter references

Fixes #16

lib/swagger_rails/rspec/dsl.rb

@@ -38,8 +38,16 @@ module SwaggerRails
         metadata[:produces] = mime_types
       end
 
+      # Accepts parameter objects:
+      #    parameter :petId, in: :path, type: :integer, required: true
+      # Or references:
+      #    parameter ref: '#/parameters/Pet'
       def parameter(name, attributes={})
-        metadata[:parameters] << { name: name.to_s }.merge(attributes)
+        metadata[:parameters] << if name.respond_to?(:has_key?)
+          { '$ref': name.delete(:ref) || name.delete('ref') }
+        else
+          { name: name.to_s }.merge(attributes)
+        end
       end
 
       def response(code, description, &block)

lib/swagger_rails/test_visitor.rb

@@ -22,12 +22,23 @@ module SwaggerRails
 
     def params_data_for(test, parameters)
       parameters.map do |parameter|
+        parameter = resolve_param_ref(parameter[:$ref]) if parameter.has_key?(:$ref)
+
         parameter
           .slice(:name, :in)
           .merge(value: test.send(parameter[:name].to_s.underscore))
       end
     end
 
+    def resolve_param_ref ref
+      raise "Invalid parameter reference: #{ref}" unless %r{#/parameters/(?<name>.+)} =~ ref
+
+      parameter = (@swagger_doc[:parameters][name] || @swagger_doc[:parameters][name.to_sym])
+      raise "Unknown parameter reference: #{ref}" unless parameter
+
+      parameter.merge(name: name)
+    end
+
     def build_path(path_template, params_data)
       path_params_data = params_data.select { |p| p[:in] == :path }