define the renderer at initialization

lib/zero/controller.rb

@@ -20,16 +20,17 @@ module Zero
       @@renderer
     end
 
-    # a small helper to get the actual renderer
-    def renderer
-      self.class.renderer
-    end
+    # the renderer which can be used to render templates
+    attr_reader :renderer
 
     # initialize the controller
+    #
+    # At initialization `@request`, `@response` and `@renderer` are set.
     # @param request [Request] a request object
     def initialize(request)
       @request  = request
       @response = Zero::Response.new
+      @renderer = self.class.renderer
     end
 
     # build the response and return it

spec/unit/controller/call_spec.rb

@@ -1,9 +1,14 @@
 require 'spec_helper'
 
 describe Zero::Controller, '.call' do
-  subject { SpecController.call(env) }
+  subject { controller.call(env) }
+  let(:controller) { SpecController }
   let(:env) { EnvGenerator.get('/foo') }
 
+  before :each do
+    controller.renderer = Object.new
+  end
+
   it "returns a response" do
     subject.should be_respond_to(:to_a)
   end