The magic medicine worked.

actionpack/lib/action_view/base.rb

@@ -153,7 +153,7 @@ module ActionView #:nodoc:
       end
     end
 
-    attr_accessor :_template, :_view_flow, :magic_medicine
+    attr_accessor :_template, :_view_flow
     attr_internal :request, :controller, :config, :assigns, :lookup_context
 
     delegate :formats, :formats=, :locale, :locale=, :view_paths, :view_paths=, :to => :lookup_context

actionpack/test/template/streaming_render_test.rb

@@ -5,23 +5,29 @@ require 'controller/fake_models'
 class TestController < ActionController::Base
 end
 
-
 class FiberedTest < ActiveSupport::TestCase
-
   def setup
     view_paths = ActionController::Base.view_paths
     @assigns = { :secret => 'in the sauce' }
     @view = ActionView::Base.new(view_paths, @assigns)
-    @view.magic_medicine = true
     @controller_view = TestController.new.view_context
   end
 
-  def test_render_template
-    assert_equal "Hello world!", @view.render(:template => "test/hello_world")
+  def buffered_render(options)
+    body = @view.render_body(options)
+    string = ""
+    body.each do |piece|
+      string << piece
+    end
+    string
   end
 
-  def test_render_with_layout
+  def test_render_template_without_layout
+    assert_equal "Hello world!", buffered_render(:template => "test/hello_world")
+  end
+
+  def test_render_template_with_layout
     assert_equal %(<title></title>\nHello world!\n),
-      @view.render(:template => "test/hello_world.erb", :layout => "layouts/yield")
+      buffered_render(:template => "test/hello_world.erb", :layout => "layouts/yield")
   end
 end if defined?(Fiber)