Refactor Plugin Loader. Add plugin lib paths early, and add lots of tests. Closes #9795 [lazyatom]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@8115 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

10 files changed, 679 insertions, 294 deletions

diff --git a/railties/CHANGELOG b/railties/CHANGELOG
index 960ad59ef3..2ee6fac28e 100644
--- a/railties/CHANGELOG
+++ b/railties/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Refactor Plugin Loader.  Add plugin lib paths early, and add lots of tests.  Closes #9795 [lazyatom]
+
 * Added --skip-timestamps to generators that produce models #10036 [tpope]
 
 * Update Prototype to 1.6.0 and script.aculo.us to 1.8.0.  [sam, madrobby]
diff --git a/railties/lib/initializer.rb b/railties/lib/initializer.rb
index 0256ba96b2..ab6549164c 100644
--- a/railties/lib/initializer.rb
+++ b/railties/lib/initializer.rb
@@ -34,7 +34,7 @@ module Rails
 
     # The set of loaded plugins.
     attr_reader :loaded_plugins
-
+    
     # Runs the initializer. By default, this will invoke the #process method,
     # which simply executes all of the initialization routines. Alternately,
     # you can specify explicitly which initialization routine you want:
@@ -64,6 +64,7 @@ module Rails
     # * #set_load_path
     # * #require_frameworks
     # * #set_autoload_paths
+    # * add_plugin_load_paths
     # * #load_environment
     # * #initialize_encoding
     # * #initialize_database
@@ -83,9 +84,10 @@ module Rails
     def process
       check_ruby_version
       set_load_path
-
+      
       require_frameworks
       set_autoload_paths
+      add_plugin_load_paths
       load_environment
 
       initialize_encoding
@@ -161,14 +163,20 @@ module Rails
     def add_support_load_paths
     end
 
+    # Adds all load paths from plugins to the global set of load paths, so that
+    # code from plugins can be required (explicitly or automatically via Dependencies).
+    def add_plugin_load_paths
+      plugin_loader.add_plugin_load_paths
+    end
+
     # Loads all plugins in <tt>config.plugin_paths</tt>.  <tt>plugin_paths</tt>
     # defaults to <tt>vendor/plugins</tt> but may also be set to a list of
     # paths, such as
     #   config.plugin_paths = ["#{RAILS_ROOT}/lib/plugins", "#{RAILS_ROOT}/vendor/plugins"]
     #
-    # Each plugin discovered in <tt>plugin_paths</tt> is initialized:
-    # * add its +lib+ directory, if present, to the beginning of the load path
-    # * evaluate <tt>init.rb</tt> if present
+    # In the default implementation, as each plugin discovered in <tt>plugin_paths</tt> is initialized:
+    # * its +lib+ directory, if present, is added to the load path (immediately after the applications lib directory)
+    # * <tt>init.rb</tt> is evalutated, if present
     #
     # After all plugins are loaded, duplicates are removed from the load path.
     # If an array of plugin names is specified in config.plugins, only those plugins will be loaded
@@ -178,13 +186,11 @@ module Rails
     # if config.plugins ends contains :all then the named plugins will be loaded in the given order and all other
     # plugins will be loaded in alphabetical order
     def load_plugins
-      configuration.plugin_locators.each do |locator|
-        locator.new(self).each do |plugin|
-          plugin.load
-        end
-      end
-      ensure_all_registered_plugins_are_loaded!
-      $LOAD_PATH.uniq!
+      plugin_loader.load_plugins
+    end
+
+    def plugin_loader
+      @plugin_loader ||= configuration.plugin_loader.new(self)
     end
 
     # Loads the environment specified by Configuration#environment_path, which
@@ -337,15 +343,6 @@ module Rails
       end
     end
 
-    private
-      def ensure_all_registered_plugins_are_loaded!
-        unless configuration.plugins.nil?
-          if configuration.plugins.detect {|plugin| plugin != :all && !loaded_plugins.include?( plugin)}
-            missing_plugins = configuration.plugins - (loaded_plugins + [:all])
-            raise LoadError, "Could not locate the following plugins: #{missing_plugins.to_sentence}"
-          end
-        end
-      end
   end
 
   # The Configuration class holds all the parameters for the Initializer and
diff --git a/railties/lib/rails/plugin.rb b/railties/lib/rails/plugin.rb
new file mode 100644
index 0000000000..2feb90bf14
--- /dev/null
+++ b/railties/lib/rails/plugin.rb
@@ -0,0 +1,83 @@
+module Rails
+
+  # The Plugin class should be an object which provides the following methods:
+  #
+  # * +name+       - used during initialisation to order the plugin (based on name and
+  #                  the contents of <tt>config.plugins</tt>)
+  # * +valid?+     - returns true if this plugin can be loaded
+  # * +load_paths+ - each path within the returned array will be added to the $LOAD_PATH
+  # * +load+       - finally 'load' the plugin.
+  #
+  # These methods are expected by the Rails::Plugin::Locator and Rails::Plugin::Loader classes.
+  # The default implementation returns the <tt>lib</tt> directory as its </tt>load_paths</tt>, 
+  # and evaluates <tt>init.rb</tt> when <tt>load</tt> is called.
+  class Plugin
+    include Comparable
+    
+    attr_reader :directory, :name
+    
+    def initialize(directory)
+      @directory = directory
+      @name = File.basename(@directory) rescue nil
+      @loaded = false
+    end
+    
+    def valid?
+      File.directory?(directory) && (has_lib_directory? || has_init_file?)
+    end
+  
+    # Returns a list of paths this plugin wishes to make available in $LOAD_PATH
+    def load_paths
+      report_nonexistant_or_empty_plugin! unless valid?
+      has_lib_directory? ? [lib_path] : []
+    end
+
+    # Evaluates a plugin's init.rb file
+    def load(initializer)
+      report_nonexistant_or_empty_plugin! unless valid?
+      evaluate_init_rb(initializer)
+      @loaded = true
+    end
+    
+    def loaded?
+      @loaded
+    end
+    
+    def <=>(other_plugin)
+      name <=> other_plugin.name
+    end
+    
+    private
+
+      def report_nonexistant_or_empty_plugin!
+        raise LoadError, "Can not find the plugin named: #{name}"
+      end      
+    
+      def lib_path
+        File.join(directory, 'lib')
+      end
+
+      def init_path
+        File.join(directory, 'init.rb')
+      end
+
+      def has_lib_directory?
+        File.directory?(lib_path)
+      end
+
+      def has_init_file?
+        File.file?(init_path)
+      end
+
+      def evaluate_init_rb(initializer)
+         if has_init_file?
+           silence_warnings do
+             # Allow plugins to reference the current configuration object
+             config = initializer.configuration
+             
+             eval(IO.read(init_path), binding, init_path)
+           end
+         end
+      end               
+  end
+end
\ No newline at end of file
diff --git a/railties/lib/rails/plugin/loader.rb b/railties/lib/rails/plugin/loader.rb
index 016bcc6c50..dcc62d50b6 100644
--- a/railties/lib/rails/plugin/loader.rb
+++ b/railties/lib/rails/plugin/loader.rb
@@ -1,146 +1,150 @@
+require "rails/plugin"
+
 module Rails
-  module Plugin
+  class Plugin
     class Loader
-      include Comparable
-      attr_reader :initializer, :directory, :name
-  
-      class << self
-        def load(*args)
-          new(*args).load
-        end
-      end
-  
-      def initialize(initializer, directory)
+      attr_reader :initializer
+
+      # Creates a new Plugin::Loader instance, associated with the given
+      # Rails::Initializer. This default implementation automatically locates
+      # all plugins, and adds all plugin load paths, when it is created. The plugins
+      # are then fully loaded (init.rb is evaluated) when load_plugins is called.
+      #
+      # It is the loader's responsibilty to ensure that only the plugins specified
+      # in the configuration are actually loaded, and that the order defined
+      # is respected.
+      def initialize(initializer)
         @initializer = initializer
-        @directory   = directory
-        @name        = File.basename(directory).to_sym
       end
-  
-      def load
-        return false if loaded?
-        report_nonexistant_or_empty_plugin!
-        add_to_load_path!
-        register_plugin_as_loaded
-        evaluate
-        true
+      
+      # Returns the plugins to be loaded, in the order they should be loaded.
+      def plugins
+        @plugins ||= all_plugins.select { |plugin| should_load?(plugin) }.sort { |p1, p2| order_plugins(p1, p2) }
       end
-  
-      def loaded?
-        initializer.loaded_plugins.include?(name)
+
+      # Returns all the plugins that could be found by the current locators.
+      def all_plugins
+        @all_plugins ||= locate_plugins
+        @all_plugins
       end
-  
-      def plugin_path?
-        File.directory?(directory) && (has_lib_directory? || has_init_file?)
+    
+      def load_plugins
+        plugins.each do |plugin| 
+          plugin.load(initializer)
+          register_plugin_as_loaded(plugin)
+        end
+        ensure_all_registered_plugins_are_loaded!
       end
       
-      def enabled?
-        !explicit_plugin_loading_order? || registered?
-      end
+      # Adds the load paths for every plugin into the $LOAD_PATH. Plugin load paths are
+      # added *after* the application's <tt>lib</tt> directory, to ensure that an application
+      # can always override code within a plugin.
+      #
+      # Plugin load paths are also added to Dependencies.load_paths, and Dependencies.load_once_paths.  
+      def add_plugin_load_paths
+        plugins.each do |plugin|
+          plugin.load_paths.each do |path|
+            $LOAD_PATH.insert(application_lib_index + 1, path)
+            Dependencies.load_paths      << path
+            Dependencies.load_once_paths << path
+          end
+        end
+        $LOAD_PATH.uniq!
+      end      
       
-      def explicitly_enabled?
-        !explicit_plugin_loading_order? || explicitly_registered?
-      end
+      protected
       
-      def registered?
-        explicit_plugin_loading_order? && registered_plugins_names_plugin?(name)
-      end
+        # The locate_plugins method uses each class in config.plugin_locators to
+        # find the set of all plugins available to this Rails application.
+        def locate_plugins
+          configuration.plugin_locators.map { |locator|
+            locator.new(initializer).plugins
+          }.flatten
+          # TODO: sorting based on config.plugins
+        end
 
-      def explicitly_registered?
-        explicit_plugin_loading_order? && registered_plugins.include?(name)
-      end
-      
-      def plugin_does_not_exist!(plugin_name = name)
-        raise LoadError, "Can not find the plugin named: #{plugin_name}"
-      end
-      
-      private
-        # The plugins that have been explicitly listed with config.plugins. If this list is nil
-        # then it means the client does not care which plugins or in what order they are loaded, 
-        # so we load all in alphabetical order. If it is an empty array, we load no plugins, if it is
-        # non empty, we load the named plugins in the order specified.
-        def registered_plugins
-          config.plugins
+        def register_plugin_as_loaded(plugin)
+          initializer.loaded_plugins << plugin
         end
-        
-        def registered_plugins_names_plugin?(plugin_name)
-          registered_plugins.include?(plugin_name) || registered_plugins.include?(:all)
+
+        def configuration
+          initializer.configuration
         end
         
-        def explicit_plugin_loading_order?
-          !registered_plugins.nil?
+        def should_load?(plugin)
+          # uses Plugin#name and Plugin#valid?
+          enabled?(plugin) && plugin.valid?
         end
-        
-        def report_nonexistant_or_empty_plugin!
-          plugin_does_not_exist! unless plugin_path?
+
+        def order_plugins(plugin_a, plugin_b)
+          if !explicit_plugin_loading_order?
+            plugin_a <=> plugin_b
+          else
+            if !explicitly_enabled?(plugin_a) && !explicitly_enabled?(plugin_b)
+              plugin_a <=> plugin_b
+            else
+              effective_order_of(plugin_a) <=> effective_order_of(plugin_b)
+            end            
+          end
         end
         
-        def lib_path
-          File.join(directory, 'lib')
+        def effective_order_of(plugin)
+          if explicitly_enabled?(plugin)
+            registered_plugin_names.index(plugin.name) 
+          else
+            registered_plugin_names.index('all')
+          end        
         end
-  
-        def init_path
-          File.join(directory, 'init.rb')
+
+        def application_lib_index
+          $LOAD_PATH.index(File.join(RAILS_ROOT, 'lib')) || 0
+        end      
+
+        def enabled?(plugin)
+          !explicit_plugin_loading_order? || registered?(plugin)
         end
-  
-        def has_lib_directory?
-          File.directory?(lib_path)
+
+        def explicit_plugin_loading_order?
+          !registered_plugin_names.nil?
         end
-  
-        def has_init_file?
-          File.file?(init_path)
+
+        def registered?(plugin)
+          explicit_plugin_loading_order? && registered_plugins_names_plugin?(plugin)
         end
-  
-        def add_to_load_path!
-          # Add lib to load path *after* the application lib, to allow
-          # application libraries to override plugin libraries.
-          if has_lib_directory?
-            application_lib_index = $LOAD_PATH.index(application_library_path) || 0
-            $LOAD_PATH.insert(application_lib_index + 1, lib_path)
-            Dependencies.load_paths      << lib_path
-            Dependencies.load_once_paths << lib_path
-          end
+
+        def explicitly_enabled?(plugin)
+          !explicit_plugin_loading_order? || explicitly_registered?(plugin)
         end
-      
-        def application_library_path
-          File.join(RAILS_ROOT, 'lib')
+
+        def explicitly_registered?(plugin)
+          explicit_plugin_loading_order? && registered_plugin_names.include?(plugin.name)
         end
-  
-        # Allow plugins to reference the current configuration object
-        def config
-          initializer.configuration
+      
+        def registered_plugins_names_plugin?(plugin)
+          registered_plugin_names.include?(plugin.name) || registered_plugin_names.include?('all')
         end
-  
-        def register_plugin_as_loaded
-          initializer.loaded_plugins << name
+        
+        # The plugins that have been explicitly listed with config.plugins. If this list is nil
+        # then it means the client does not care which plugins or in what order they are loaded, 
+        # so we load all in alphabetical order. If it is an empty array, we load no plugins, if it is
+        # non empty, we load the named plugins in the order specified.
+        def registered_plugin_names
+          configuration.plugins ? configuration.plugins.map(&:to_s) : nil
         end
-  
-        # Evaluate in init.rb
-        def evaluate
-          silence_warnings { eval(IO.read(init_path), binding, init_path) } if has_init_file?
+        
+        def loaded?(plugin_name)
+          initializer.loaded_plugins.detect { |plugin| plugin.name == plugin_name.to_s }
         end
-      
-        def <=>(other_plugin_loader)
+        
+        def ensure_all_registered_plugins_are_loaded!
           if explicit_plugin_loading_order?
-            if non_existent_plugin = [self, other_plugin_loader].detect { |plugin| !registered_plugins_names_plugin?(plugin.name) }
-              plugin_does_not_exist!(non_existent_plugin.name)
-            end
-            
-            if !explicitly_enabled? && !other_plugin_loader.explicitly_enabled?
-              name.to_s <=> other_plugin_loader.name.to_s
-            elsif registered_plugins.include?(:all) && (!explicitly_enabled? || !other_plugin_loader.explicitly_enabled?)
-              effective_index = explicitly_enabled? ? registered_plugins.index(name) : registered_plugins.index(:all)
-              other_effective_index = other_plugin_loader.explicitly_enabled? ? 
-                registered_plugins.index(other_plugin_loader.name) : registered_plugins.index(:all)
-
-              effective_index <=> other_effective_index
-            else
-              registered_plugins.index(name) <=> registered_plugins.index(other_plugin_loader.name)
+            if configuration.plugins.detect {|plugin| plugin != :all && !loaded?(plugin) }
+              missing_plugins = configuration.plugins - (plugins + [:all])
+              raise LoadError, "Could not locate the following plugins: #{missing_plugins.to_sentence}"
             end
-            
-          else
-            name.to_s <=> other_plugin_loader.name.to_s
           end
         end
+  
     end
   end
 end
\ No newline at end of file
diff --git a/railties/lib/rails/plugin/locator.rb b/railties/lib/rails/plugin/locator.rb
index 6c4f2605bb..b27e904b12 100644
--- a/railties/lib/rails/plugin/locator.rb
+++ b/railties/lib/rails/plugin/locator.rb
@@ -1,15 +1,23 @@
 module Rails
-  module Plugin
+  class Plugin
+    
+    # The Plugin::Locator class should be subclasses to provide custom plugin-finding
+    # abilities to Rails (i.e. loading plugins from Gems, etc). Each subclass should implement
+    # the <tt>located_plugins</tt> method, which return an array of Plugin objects that have been found.
     class Locator
       include Enumerable
+      
       attr_reader :initializer
       
       def initialize(initializer)
         @initializer = initializer
       end
       
+      # This method should return all the plugins which this Plugin::Locator can find
+      # These will then be used by the current Plugin::Loader, which is responsible for actually
+      # loading the plugins themselves
       def plugins
-        located_plugins.select(&:enabled?).sort
+        raise "The `plugins' method must be defined by concrete subclasses of #{self.class}"
       end
       
       def each(&block)
@@ -19,41 +27,52 @@ module Rails
       def plugin_names
         plugins.map(&:name)
       end
-      
-      private
-        def located_plugins
-          raise "The `located_plugins' method must be defined by concrete subclasses of #{self.class}"
-        end
     end
     
+    # The Rails::Plugin::FileSystemLocator will try to locate plugins by examining the directories
+    # the the paths given in configuration.plugin_paths. Any plugins that can be found are returned
+    # in a list. 
+    #
+    # The criteria for a valid plugin in this case is found in Rails::Plugin#valid?, although
+    # other subclasses of Rails::Plugin::Locator can of course use different conditions.
     class FileSystemLocator < Locator
-        private
-          def located_plugins
-            initializer.configuration.plugin_paths.flatten.inject([]) do |plugins, path|
-              plugins.concat locate_plugins_under(path)
-              plugins
-            end.flatten
-          end
+      
+      # Returns all the plugins which can be loaded in the filesystem, under the paths given
+      # by configuration.plugin_paths.
+      def plugins
+        initializer.configuration.plugin_paths.flatten.inject([]) do |plugins, path|
+          plugins.concat locate_plugins_under(path)
+          plugins
+        end.flatten
+      end
+          
+      private
+      
+        # Attempts to create a plugin from the given path. If the created plugin is valid?
+        # (see Rails::Plugin#valid?) then the plugin instance is returned; otherwise nil.
+        def create_plugin(path)
+          plugin = Rails::Plugin.new(path)
+          plugin.valid? ? plugin : nil
+        end
 
-          # This starts at the base path looking for directories that pass the plugin_path? test of the Plugin::Loader.
-          # Since plugins can be nested arbitrarily deep within an unspecified number of intermediary directories, 
-          # this method runs recursively until it finds a plugin directory.
-          #
-          #   e.g.
-          #
-          #     locate_plugins_under('vendor/plugins/acts/acts_as_chunky_bacon')
-          #     => 'acts_as_chunky_bacon' 
-          def locate_plugins_under(base_path)
-             Dir.glob(File.join(base_path, '*')).inject([]) do |plugins, path|
-              plugin_loader = initializer.configuration.plugin_loader.new(initializer, path)
-              if plugin_loader.plugin_path? && plugin_loader.enabled?
-                plugins << plugin_loader
-              elsif File.directory?(path)
-                plugins.concat locate_plugins_under(path)
-              end
-              plugins
+        # This starts at the base path looking for valid plugins (see Rails::Plugin#valid?).
+        # Since plugins can be nested arbitrarily deep within an unspecified number of intermediary 
+        # directories, this method runs recursively until it finds a plugin directory, e.g.
+        #
+        #     locate_plugins_under('vendor/plugins/acts/acts_as_chunky_bacon')
+        #     => <Rails::Plugin name: 'acts_as_chunky_bacon' ... >
+        #
+        def locate_plugins_under(base_path)
+           Dir.glob(File.join(base_path, '*')).inject([]) do |plugins, path|
+            if plugin = create_plugin(path)
+              plugins << plugin
+            elsif File.directory?(path)
+              plugins.concat locate_plugins_under(path)
             end
+            plugins
           end
+        end
+        
     end
   end
 end
\ No newline at end of file
diff --git a/railties/test/initializer_test.rb b/railties/test/initializer_test.rb
index 5707a63258..156f670e87 100644
--- a/railties/test/initializer_test.rb
+++ b/railties/test/initializer_test.rb
@@ -135,3 +135,84 @@ uses_mocha 'framework paths' do
       end
   end
 end
+
+uses_mocha "Initializer plugin loading tests" do
+  require File.dirname(__FILE__) + '/plugin_test_helper'
+
+  class InitializerPluginLoadingTests < Test::Unit::TestCase
+    def setup
+      @configuration     = Rails::Configuration.new
+      @configuration.plugin_paths << plugin_fixture_root_path
+      @initializer       = Rails::Initializer.new(@configuration)
+      @valid_plugin_path = plugin_fixture_path('default/stubby')
+      @empty_plugin_path = plugin_fixture_path('default/empty')
+    end
+
+    def test_no_plugins_are_loaded_if_the_configuration_has_an_empty_plugin_list
+      only_load_the_following_plugins! []
+      @initializer.load_plugins
+      assert_equal [], @initializer.loaded_plugins
+    end
+
+    def test_only_the_specified_plugins_are_located_in_the_order_listed
+      plugin_names = [:plugin_with_no_lib_dir, :acts_as_chunky_bacon]
+      only_load_the_following_plugins! plugin_names
+      load_plugins!
+      assert_plugins plugin_names, @initializer.loaded_plugins
+    end
+
+    def test_all_plugins_are_loaded_when_registered_plugin_list_is_untouched
+      failure_tip = "It's likely someone has added a new plugin fixture without updating this list"
+      load_plugins!
+      assert_plugins [:a, :acts_as_chunky_bacon, :plugin_with_no_lib_dir, :stubby], @initializer.loaded_plugins, failure_tip
+    end
+
+    def test_all_plugins_loaded_when_all_is_used
+      plugin_names = [:stubby, :acts_as_chunky_bacon, :all]
+      only_load_the_following_plugins! plugin_names
+      load_plugins!
+      failure_tip = "It's likely someone has added a new plugin fixture without updating this list"
+      assert_plugins [:stubby, :acts_as_chunky_bacon, :a, :plugin_with_no_lib_dir], @initializer.loaded_plugins, failure_tip
+    end
+
+    def test_all_plugins_loaded_after_all
+      plugin_names = [:stubby, :all, :acts_as_chunky_bacon]
+      only_load_the_following_plugins! plugin_names
+      load_plugins!
+      failure_tip = "It's likely someone has added a new plugin fixture without updating this list"
+      assert_plugins [:stubby, :a, :plugin_with_no_lib_dir, :acts_as_chunky_bacon], @initializer.loaded_plugins, failure_tip
+    end
+
+    def test_plugin_names_may_be_strings
+      plugin_names = ['stubby', 'acts_as_chunky_bacon', :a, :plugin_with_no_lib_dir]
+      only_load_the_following_plugins! plugin_names
+      load_plugins!
+      failure_tip = "It's likely someone has added a new plugin fixture without updating this list"
+      assert_plugins plugin_names, @initializer.loaded_plugins, failure_tip
+    end
+
+    def test_registering_a_plugin_name_that_does_not_exist_raises_a_load_error
+      only_load_the_following_plugins! [:stubby, :acts_as_a_non_existant_plugin]
+      assert_raises(LoadError) do
+        load_plugins!
+      end
+    end
+    
+    def test_should_ensure_all_loaded_plugins_load_paths_are_added_to_the_load_path
+      only_load_the_following_plugins! [:stubby, :acts_as_chunky_bacon]
+
+      @initializer.add_plugin_load_paths
+      
+      assert $LOAD_PATH.include?(File.join(plugin_fixture_path('default/stubby'), 'lib'))
+      assert $LOAD_PATH.include?(File.join(plugin_fixture_path('default/acts/acts_as_chunky_bacon'), 'lib'))
+    end
+    
+    private
+    
+      def load_plugins!
+        @initializer.add_plugin_load_paths
+        @initializer.load_plugins
+      end
+  end
+  
+end  
diff --git a/railties/test/plugin_loader_test.rb b/railties/test/plugin_loader_test.rb
index 3c2c37e794..fe77de4474 100644
--- a/railties/test/plugin_loader_test.rb
+++ b/railties/test/plugin_loader_test.rb
@@ -1,90 +1,140 @@
 require File.dirname(__FILE__) + '/plugin_test_helper'
 
-class TestPluginLoader < Test::Unit::TestCase
-  def setup
-    @initializer       = Rails::Initializer.new(Rails::Configuration.new)
-    @valid_plugin_path = plugin_fixture_path('default/stubby')
-    @empty_plugin_path = plugin_fixture_path('default/empty')
-  end
-  
-  def test_determining_if_the_plugin_order_has_been_explicitly_set
-    loader = loader_for(@valid_plugin_path)
-    assert !loader.send(:explicit_plugin_loading_order?)
-    only_load_the_following_plugins! %w(stubby acts_as_chunky_bacon)
-    assert loader.send(:explicit_plugin_loading_order?)
-  end
-  
-  def test_enabled_if_not_named_explicitly
-    stubby_loader = loader_for(@valid_plugin_path)
-    acts_as_loader = loader_for('acts_as/acts_as_chunky_bacon')
+uses_mocha "Plugin Loader Tests" do
+
+  class TestPluginLoader < Test::Unit::TestCase
+    ORIGINAL_LOAD_PATH = $LOAD_PATH.dup
     
-    only_load_the_following_plugins! ['stubby', :all]
-    assert stubby_loader.send(:enabled?)
-    assert acts_as_loader.send(:enabled?)
+    def setup
+      reset_load_path!
+      
+      @configuration     = Rails::Configuration.new
+      @configuration.plugin_paths << plugin_fixture_root_path
+      @initializer       = Rails::Initializer.new(@configuration)
+      @valid_plugin_path = plugin_fixture_path('default/stubby')
+      @empty_plugin_path = plugin_fixture_path('default/empty')
+      
+      @loader = Rails::Plugin::Loader.new(@initializer)
+    end
+
+    def test_should_locate_plugins_by_asking_each_locator_specifed_in_configuration_for_its_plugins_result
+      locator_1 = stub(:plugins => [:a, :b, :c])
+      locator_2 = stub(:plugins => [:d, :e, :f])
+      locator_class_1 = stub(:new => locator_1)
+      locator_class_2 = stub(:new => locator_2)
+      @configuration.plugin_locators = [locator_class_1, locator_class_2]
+      assert_equal [:a, :b, :c, :d, :e, :f], @loader.send(:locate_plugins)
+    end
     
-    assert stubby_loader.send(:explicitly_enabled?)
-    assert !acts_as_loader.send(:explicitly_enabled?)
-  end
-  
-  def test_determining_whether_a_given_plugin_is_loaded
-    plugin_loader = loader_for(@valid_plugin_path)
-    assert !plugin_loader.loaded?
-    assert_nothing_raised do
-      plugin_loader.send(:register_plugin_as_loaded)
-    end
-    assert plugin_loader.loaded?
-  end
-  
-  def test_if_a_path_is_a_plugin_path
-    # This is a plugin path, with a lib dir
-    assert loader_for(@valid_plugin_path).plugin_path?
-    # This just has an init.rb and no lib dir
-    assert loader_for(plugin_fixture_path('default/plugin_with_no_lib_dir')).plugin_path?
-    # This would be a plugin path, but the directory is empty
-    assert !loader_for(plugin_fixture_path('default/empty')).plugin_path?
-    # This is a non sense path
-    assert !loader_for(plugin_fixture_path('default/this_directory_does_not_exist')).plugin_path?
-  end
-  
-  def test_if_you_try_to_load_a_non_plugin_path_you_get_a_load_error
-    # This path is fine so nothing is raised
-    assert_nothing_raised do
-      loader_for(@valid_plugin_path).send(:report_nonexistant_or_empty_plugin!)
+    def test_should_memoize_the_result_of_locate_plugins_as_all_plugins
+      plugin_list = [:a, :b, :c]
+      @loader.expects(:locate_plugins).once.returns(plugin_list)
+      assert_equal plugin_list, @loader.all_plugins
+      assert_equal plugin_list, @loader.all_plugins # ensuring that locate_plugins isn't called again
     end
     
-    # This is an empty path so it raises
-    assert_raises(LoadError) do
-      loader_for(@empty_plugin_path).send(:report_nonexistant_or_empty_plugin!)
+    def test_should_return_empty_array_if_configuration_plugins_is_empty
+      @configuration.plugins = []
+      assert_equal [], @loader.plugins
     end
     
-    assert_raises(LoadError) do
-      loader_for('this_is_not_a_plugin_directory').send(:report_nonexistant_or_empty_plugin!)
+    def test_should_find_all_availble_plugins_and_return_as_all_plugins
+      failure_tip = "It's likely someone has added a new plugin fixture without updating this list"
+      assert_plugins [:a, :acts_as_chunky_bacon, :plugin_with_no_lib_dir, :stubby], @loader.all_plugins, failure_tip      
     end
-  end
-  
-  def test_loading_a_plugin_gives_the_init_file_access_to_all_it_needs
-    failure_tip = "Perhaps someone has written another test that loads this same plugin and therefore makes the StubbyMixin constant defined already."
-    assert !defined?(StubbyMixin), failure_tip
-    assert !added_to_load_path?(@valid_plugin_path)
-    # The init.rb of this plugin raises if it doesn't have access to all the things it needs
-    assert_nothing_raised do
-      loader_for(@valid_plugin_path).load
-    end
-    assert added_to_load_path?(@valid_plugin_path)
-    assert defined?(StubbyMixin)
-  end
-  
-  private
-    def loader_for(path, initializer = @initializer)
-      Rails::Plugin::Loader.new(initializer, path)
+
+    def test_should_return_all_plugins_as_plugins_when_registered_plugin_list_is_untouched
+      failure_tip = "It's likely someone has added a new plugin fixture without updating this list"
+      assert_plugins [:a, :acts_as_chunky_bacon, :plugin_with_no_lib_dir, :stubby], @loader.plugins, failure_tip
+    end
+    
+    def test_should_return_all_plugins_as_plugins_when_registered_plugin_list_is_nil
+      @configuration.plugins = nil
+      failure_tip = "It's likely someone has added a new plugin fixture without updating this list"
+      assert_plugins [:a, :acts_as_chunky_bacon, :plugin_with_no_lib_dir, :stubby], @loader.plugins, failure_tip
+    end
+
+    def test_should_return_specific_plugins_named_in_config_plugins_array_if_set
+      plugin_names = [:acts_as_chunky_bacon, :stubby]
+      only_load_the_following_plugins! plugin_names
+      assert_plugins plugin_names, @loader.plugins
+    end
+    
+    def test_should_respect_the_order_of_plugins_given_in_configuration
+      plugin_names = [:stubby, :acts_as_chunky_bacon]
+      only_load_the_following_plugins! plugin_names
+      assert_plugins plugin_names, @loader.plugins      
+    end
+    
+    def test_should_load_all_plugins_in_natural_order_when_all_is_used
+      only_load_the_following_plugins! [:all]
+      failure_tip = "It's likely someone has added a new plugin fixture without updating this list"
+      assert_plugins [:a, :acts_as_chunky_bacon, :plugin_with_no_lib_dir, :stubby], @loader.plugins, failure_tip
     end
     
-    def plugin_fixture_path(path)
-      File.join(plugin_fixture_root_path, path)
+    def test_should_load_specified_plugins_in_order_and_then_all_remaining_plugins_when_all_is_used
+      only_load_the_following_plugins! [:stubby, :acts_as_chunky_bacon, :all]
+      failure_tip = "It's likely someone has added a new plugin fixture without updating this list"
+      assert_plugins [:stubby, :acts_as_chunky_bacon, :a, :plugin_with_no_lib_dir], @loader.plugins, failure_tip
     end
     
-    def added_to_load_path?(path)
-      $LOAD_PATH.grep(/#{path}/).size == 1
+    def test_should_be_able_to_specify_loading_of_plugins_loaded_after_all
+      only_load_the_following_plugins!  [:stubby, :all, :acts_as_chunky_bacon]
+      failure_tip = "It's likely someone has added a new plugin fixture without updating this list"
+      assert_plugins [:stubby, :a, :plugin_with_no_lib_dir, :acts_as_chunky_bacon], @loader.plugins, failure_tip
+    end
+
+    def test_should_accept_plugin_names_given_as_strings
+      only_load_the_following_plugins! ['stubby', 'acts_as_chunky_bacon', :a, :plugin_with_no_lib_dir]
+      failure_tip = "It's likely someone has added a new plugin fixture without updating this list"
+      assert_plugins [:stubby, :acts_as_chunky_bacon, :a, :plugin_with_no_lib_dir], @loader.plugins, failure_tip
+    end
+    
+    def test_should_add_plugin_load_paths_to_global_LOAD_PATH_array
+      only_load_the_following_plugins! [:stubby, :acts_as_chunky_bacon]
+      stubbed_application_lib_index_in_LOAD_PATHS = 5
+      @loader.stubs(:application_lib_index).returns(stubbed_application_lib_index_in_LOAD_PATHS)
+      
+      @loader.add_plugin_load_paths
+      
+      assert $LOAD_PATH.index(File.join(plugin_fixture_path('default/stubby'), 'lib')) >= stubbed_application_lib_index_in_LOAD_PATHS
+      assert $LOAD_PATH.index(File.join(plugin_fixture_path('default/acts/acts_as_chunky_bacon'), 'lib')) >= stubbed_application_lib_index_in_LOAD_PATHS    
+    end   
+    
+    def test_should_add_plugin_load_paths_to_Dependencies_load_paths
+      only_load_the_following_plugins! [:stubby, :acts_as_chunky_bacon]
+
+      @loader.add_plugin_load_paths
+      
+      assert Dependencies.load_paths.include?(File.join(plugin_fixture_path('default/stubby'), 'lib'))
+      assert Dependencies.load_paths.include?(File.join(plugin_fixture_path('default/acts/acts_as_chunky_bacon'), 'lib'))    
     end
     
+    def test_should_add_plugin_load_paths_to_Dependencies_load_once_paths
+      only_load_the_following_plugins! [:stubby, :acts_as_chunky_bacon]
+
+      @loader.add_plugin_load_paths
+      
+      assert Dependencies.load_once_paths.include?(File.join(plugin_fixture_path('default/stubby'), 'lib'))
+      assert Dependencies.load_once_paths.include?(File.join(plugin_fixture_path('default/acts/acts_as_chunky_bacon'), 'lib'))    
+    end
+    
+    def test_should_add_all_load_paths_from_a_plugin_to_LOAD_PATH_array
+      plugin_load_paths = ["a", "b"]
+      plugin = stub(:load_paths => plugin_load_paths)
+      @loader.stubs(:plugins).returns([plugin])
+      
+      @loader.add_plugin_load_paths
+      
+      plugin_load_paths.each { |path| assert $LOAD_PATH.include?(path) }
+    end
+    
+    private
+    
+      def reset_load_path!
+        $LOAD_PATH.clear
+        ORIGINAL_LOAD_PATH.each { |path| $LOAD_PATH << path }        
+      end
+  end
+    
 end
\ No newline at end of file
diff --git a/railties/test/plugin_locator_test.rb b/railties/test/plugin_locator_test.rb
index 3ac4493d47..ccd270dd10 100644
--- a/railties/test/plugin_locator_test.rb
+++ b/railties/test/plugin_locator_test.rb
@@ -1,61 +1,69 @@
 require File.dirname(__FILE__) + '/plugin_test_helper'
 
-class TestPluginFileSystemLocator < Test::Unit::TestCase
-  def setup
-    configuration = Rails::Configuration.new
-    # We need to add our testing plugin directory to the plugin paths so
-    # the locator knows where to look for our plugins
-    configuration.plugin_paths << plugin_fixture_root_path
-    @initializer = Rails::Initializer.new(configuration)
-    @locator     = new_locator
-  end
+uses_mocha "Plugin Locator Tests" do
+
+  class PluginLocatorTest < Test::Unit::TestCase
   
-  def test_no_plugins_are_loaded_if_the_configuration_has_an_empty_plugin_list
-    only_load_the_following_plugins! []
-    assert_equal [], @locator.plugins
-  end
+    def test_should_require_subclasses_to_implement_the_plugins_method
+      assert_raises(RuntimeError) do
+        Rails::Plugin::Locator.new(nil).plugins
+      end
+    end
   
-  def test_only_the_specified_plugins_are_located_in_the_order_listed
-    plugin_names = [:stubby, :acts_as_chunky_bacon]
-    only_load_the_following_plugins! plugin_names
-    assert_equal plugin_names, @locator.plugin_names
-  end
+    def test_should_iterator_over_plugins_returned_by_plugins_when_calling_each
+      locator = Rails::Plugin::Locator.new(nil)
+      locator.stubs(:plugins).returns([:a, :b, :c])
+      plugin_consumer = mock
+      plugin_consumer.expects(:consume).with(:a)
+      plugin_consumer.expects(:consume).with(:b)
+      plugin_consumer.expects(:consume).with(:c)
+    
+      locator.each do |plugin|
+        plugin_consumer.consume(plugin)
+      end
+    end
   
-  def test_all_plugins_are_loaded_when_registered_plugin_list_is_untouched
-    failure_tip = "It's likely someone has added a new plugin fixture without updating this list"
-    assert_equal [:a, :acts_as_chunky_bacon, :plugin_with_no_lib_dir, :stubby], @locator.plugin_names, failure_tip
   end
+
+
+  class PluginFileSystemLocatorTest < Test::Unit::TestCase
+    def setup
+      @configuration = Rails::Configuration.new
+      # We need to add our testing plugin directory to the plugin paths so
+      # the locator knows where to look for our plugins
+      @configuration.plugin_paths << plugin_fixture_root_path
+      @initializer       = Rails::Initializer.new(@configuration)
+      @locator           = Rails::Plugin::FileSystemLocator.new(@initializer)
+      @valid_plugin_path = plugin_fixture_path('default/stubby')
+      @empty_plugin_path = plugin_fixture_path('default/empty')
+    end
+
+    def test_should_return_rails_plugin_instances_when_calling_create_plugin_with_a_valid_plugin_directory
+      assert_kind_of Rails::Plugin, @locator.send(:create_plugin, @valid_plugin_path)  
+    end
   
-  def test_all_plugins_loaded_when_all_is_used
-    plugin_names = [:stubby, :acts_as_chunky_bacon, :all]
-    only_load_the_following_plugins! plugin_names
-    failure_tip = "It's likely someone has added a new plugin fixture without updating this list"
-    assert_equal [:stubby, :acts_as_chunky_bacon, :a, :plugin_with_no_lib_dir], @locator.plugin_names, failure_tip
-  end
+    def test_should_return_nil_when_calling_create_plugin_with_an_invalid_plugin_directory
+      assert_nil @locator.send(:create_plugin, @empty_plugin_path)  
+    end
   
-  def test_all_plugins_loaded_after_all
-    plugin_names = [:stubby, :all, :acts_as_chunky_bacon]
-    only_load_the_following_plugins! plugin_names
-    failure_tip = "It's likely someone has added a new plugin fixture without updating this list"
-    assert_equal [:stubby, :a, :plugin_with_no_lib_dir, :acts_as_chunky_bacon], @locator.plugin_names, failure_tip
-  end
+    def test_should_return_all_plugins_found_under_the_set_plugin_paths
+      assert_equal ["a", "acts_as_chunky_bacon", "plugin_with_no_lib_dir", "stubby"], @locator.plugins.map(&:name)
+    end
   
-  def test_plugin_names_may_be_strings
-    plugin_names = ['stubby', 'acts_as_chunky_bacon', :a, :plugin_with_no_lib_dir]
-    only_load_the_following_plugins! plugin_names
-    failure_tip = "It's likely someone has added a new plugin fixture without updating this list"
-    assert_equal [:stubby, :acts_as_chunky_bacon, :a, :plugin_with_no_lib_dir], @locator.plugin_names, failure_tip
-  end
+    def test_should_find_plugins_only_under_the_plugin_paths_set_in_configuration
+      @configuration.plugin_paths = [File.join(plugin_fixture_root_path, "default")]
+      assert_equal ["acts_as_chunky_bacon", "plugin_with_no_lib_dir", "stubby"], @locator.plugins.map(&:name)
+    
+      @configuration.plugin_paths = [File.join(plugin_fixture_root_path, "alternate")]
+      assert_equal ["a"], @locator.plugins.map(&:name)
+    end
   
-  def test_registering_a_plugin_name_that_does_not_exist_raises_a_load_error
-    only_load_the_following_plugins! [:stubby, :acts_as_a_non_existant_plugin]
-    assert_raises(LoadError) do
-      @initializer.load_plugins
+    def test_should_not_raise_any_error_and_return_no_plugins_if_the_plugin_path_value_does_not_exist
+      @configuration.plugin_paths = ["some_missing_directory"]
+      assert_nothing_raised do
+        assert @locator.plugins.empty?
+      end
     end
   end
-  
-  private
-    def new_locator(initializer = @initializer)
-      Rails::Plugin::FileSystemLocator.new(initializer)
-    end   
-end
\ No newline at end of file
+
+end # uses_mocha
\ No newline at end of file
diff --git a/railties/test/plugin_test.rb b/railties/test/plugin_test.rb
new file mode 100644
index 0000000000..a791e42ae8
--- /dev/null
+++ b/railties/test/plugin_test.rb
@@ -0,0 +1,130 @@
+require File.dirname(__FILE__) + '/plugin_test_helper'
+
+uses_mocha "Plugin Tests" do
+
+  class PluginTest < Test::Unit::TestCase
+
+    def setup
+      @initializer       = Rails::Initializer.new(Rails::Configuration.new)
+      @valid_plugin_path = plugin_fixture_path('default/stubby')
+      @empty_plugin_path = plugin_fixture_path('default/empty')    
+    end
+
+    def test_should_determine_plugin_name_from_the_directory_of_the_plugin
+      assert_equal 'stubby', plugin_for(@valid_plugin_path).name
+      assert_equal 'empty', plugin_for(@empty_plugin_path).name
+    end
+
+    def test_should_not_be_loaded_when_created
+      assert !plugin_for(@valid_plugin_path).loaded?
+    end
+
+    def test_should_be_marked_as_loaded_when_load_is_called
+      plugin = plugin_for(@valid_plugin_path)
+      assert !plugin.loaded?
+      plugin.stubs(:evaluate_init_rb)
+      assert_nothing_raised do
+        plugin.send(:load, anything)
+      end
+      assert plugin.loaded?
+    end
+  
+    def test_should_determine_validity_of_given_path
+      # This is a plugin path, with a lib dir
+      assert plugin_for(@valid_plugin_path).valid?
+      # This just has an init.rb and no lib dir
+      assert plugin_for(plugin_fixture_path('default/plugin_with_no_lib_dir')).valid?
+      # This would be a plugin path, but the directory is empty
+      assert !plugin_for(plugin_fixture_path('default/empty')).valid?
+      # This is a non sense path
+      assert !plugin_for(plugin_fixture_path('default/this_directory_does_not_exist')).valid?
+    end
+  
+    def test_should_return_empty_array_for_load_paths_when_plugin_has_no_lib_directory
+      assert_equal [], plugin_for(plugin_fixture_path('default/plugin_with_no_lib_dir')).load_paths
+    end
+  
+    def test_should_return_array_with_lib_path_for_load_paths_when_plugin_has_a_lib_directory
+      expected_lib_dir = File.join(plugin_fixture_path('default/stubby'), 'lib')
+      assert_equal [expected_lib_dir], plugin_for(plugin_fixture_path('default/stubby')).load_paths
+    end
+  
+    def test_should_raise_a_load_error_when_trying_to_determine_the_load_paths_from_an_invalid_plugin
+      assert_nothing_raised do
+        plugin_for(@valid_plugin_path).load_paths
+      end
+    
+      assert_raises(LoadError) do
+        plugin_for(@empty_plugin_path).load_paths
+      end
+    
+      assert_raises(LoadError) do
+        plugin_for('this_is_not_a_plugin_directory').load_paths
+      end
+    end
+  
+    def test_should_raise_a_load_error_when_trying_to_load_an_invalid_plugin
+      # This path is fine so nothing is raised
+      assert_nothing_raised do
+        plugin = plugin_for(@valid_plugin_path)
+        plugin.stubs(:evaluate_init_rb)
+        plugin.send(:load, @initializer)
+      end
+    
+      # This is an empty path so it raises
+      assert_raises(LoadError) do
+        plugin = plugin_for(@empty_plugin_path)
+        plugin.stubs(:evaluate_init_rb)      
+        plugin.send(:load, @initializer)
+      end
+    
+      assert_raises(LoadError) do
+        plugin = plugin_for('this_is_not_a_plugin_directory')
+        plugin.stubs(:evaluate_init_rb)
+        plugin.send(:load, @initializer)
+      end
+    end
+    
+    def test_should_raise_a_load_error_when_trying_to_access_load_paths_of_an_invalid_plugin
+      # This path is fine so nothing is raised
+      assert_nothing_raised do
+        plugin_for(@valid_plugin_path).load_paths
+      end
+    
+      # This is an empty path so it raises
+      assert_raises(LoadError) do
+        plugin_for(@empty_plugin_path).load_paths
+      end
+    
+      assert_raises(LoadError) do
+        plugin_for('this_is_not_a_plugin_directory').load_paths
+      end
+    end    
+  
+    def test_loading_a_plugin_gives_the_init_file_access_to_all_it_needs
+      failure_tip = "Perhaps someone has written another test that loads this same plugin and therefore makes the StubbyMixin constant defined already."
+      assert !defined?(StubbyMixin), failure_tip
+      plugin = plugin_for(@valid_plugin_path)
+      plugin.load_paths.each { |path| $LOAD_PATH.unshift(path) }
+      # The init.rb of this plugin raises if it doesn't have access to all the things it needs
+      assert_nothing_raised do
+        plugin.load(@initializer)
+      end
+      assert defined?(StubbyMixin)
+    end
+    
+    def test_should_sort_naturally_by_name
+      a = plugin_for("path/a")
+      b = plugin_for("path/b")
+      z = plugin_for("path/z")
+      assert_equal [a, b, z], [b, z, a].sort
+    end
+  
+    private
+  
+      def plugin_for(path)
+        Rails::Plugin.new(path)
+      end
+  end
+
+end # uses_mocha
\ No newline at end of file
diff --git a/railties/test/plugin_test_helper.rb b/railties/test/plugin_test_helper.rb
index 0b065a5444..f8c094d19f 100644
--- a/railties/test/plugin_test_helper.rb
+++ b/railties/test/plugin_test_helper.rb
@@ -4,15 +4,26 @@ $:.unshift File.dirname(__FILE__) + "/../../activesupport/lib"
 require 'test/unit'
 require 'active_support'
 require 'initializer'
+require File.join(File.dirname(__FILE__), 'abstract_unit')
 
 # We need to set RAILS_ROOT if it isn't already set
 RAILS_ROOT = '.' unless defined?(RAILS_ROOT)
+
 class Test::Unit::TestCase
-  def plugin_fixture_root_path
-    File.join(File.dirname(__FILE__), 'fixtures', 'plugins')
-  end
+  private  
+    def plugin_fixture_root_path
+      File.join(File.dirname(__FILE__), 'fixtures', 'plugins')
+    end
+  
+    def only_load_the_following_plugins!(plugins)
+      @initializer.configuration.plugins = plugins
+    end
   
-  def only_load_the_following_plugins!(plugins)
-    @initializer.configuration.plugins = plugins
-  end
+    def plugin_fixture_path(path)
+      File.join(plugin_fixture_root_path, path)
+    end
+    
+    def assert_plugins(list_of_names, array_of_plugins, message=nil)
+      assert_equal list_of_names.map(&:to_s), array_of_plugins.map(&:name), message
+    end    
 end
\ No newline at end of file