Initialize ivars in tests.

actionpack/test/controller/caching_test.rb

@@ -185,6 +185,7 @@ class ActionCachingTestController < CachingController
 
   def with_layout
     @cache_this = MockTime.now.to_f.to_s
+    @title = nil
     render :text => @cache_this, :layout => true
   end
 

actionpack/test/controller/render_other_test.rb

@@ -120,6 +120,7 @@ class RenderOtherTest < ActionController::TestCase
 
     private
       def default_render
+        @alternate_default_render ||= nil
         if @alternate_default_render
           @alternate_default_render.call
         else

actionpack/test/controller/webservice_test.rb

@@ -24,6 +24,7 @@ class WebServiceTest < ActionDispatch::IntegrationTest
 
   def setup
     @controller = TestController.new
+    @integration_session = nil
   end
 
   def test_check_parameters