Assert that plist engine respond to #dump

lib/rabl-rails.rb

@@ -33,7 +33,7 @@ module RablRails
   mattr_accessor :responder_default_template
   @@responder_default_template = 'show'
 
-  mattr_accessor :plist_engine
+  mattr_reader :plist_engine
   @@plist_engine = nil
 
   mattr_accessor :include_plist_root
@@ -65,6 +65,11 @@ module RablRails
     ActiveSupport::XmlMini.backend
   end
 
+  def self.plist_engine=(name)
+    raise "Your plist engine does not respond to #dump" unless name.respond_to?(:dump)
+    @@plist_engine = name
+  end
+
   def self.cache_templates?
     ActionController::Base.perform_caching && @@cache_templates
   end

test/renderers/plist_renderer_test.rb

@@ -1,4 +1,7 @@
 require 'test_helper'
+require 'plist'
+
+RablRails.plist_engine = Plist::Emit
 
 class TestPlistRenderer < ActiveSupport::TestCase
   INDENT_REGEXP = /\n(\s)*/
@@ -20,6 +23,10 @@ class TestPlistRenderer < ActiveSupport::TestCase
     output.sub!(HEADER_REGEXP, '').gsub!(%r(</?plist[^>]*>), '').sub!(%r(<dict/?>), '').sub(%r(</dict>), '')
   end
 
+  test "plist engine should responsd to #dump" do
+    assert_raises(RuntimeError) { RablRails.plist_engine = Object.new }
+  end
+
   test "render object wth empty template" do
     @template.source = {}
     assert_equal %q(), render_plist_output

test/test_helper.rb

@@ -22,9 +22,6 @@ class <<Singleton
 end
 
 require 'rabl-rails'
-require 'plist'
-
-RablRails.plist_engine = Plist::Emit
 
 module ActiveSupport
   class TestCase