diff --git a/railties/lib/generators.rb b/railties/lib/generators.rb
index ee17242940ccf5a39e8fef5d24fbce5b938f7f92..a923a3339707c34ff902f92817761a749219a0fc 100644
--- a/railties/lib/generators.rb
+++ b/railties/lib/generators.rb
@@ -16,7 +16,6 @@
 
 module Rails
   module Generators
-    mattr_accessor :load_path
 
     # Generators load paths. First search on generators in the RAILS_ROOT, then
     # look for them in rails generators.
@@ -33,42 +32,6 @@ def self.load_path
     end
     load_path # Cache load paths
 
-    # Receives paths in an array and tries to find generators for it in the load
-    # path.
-    #
-    def self.lookup(attempts)
-      generators_path = []
-
-      # Traverse attempts into directory lookups. For example:
-      #
-      #   rails:generators:model
-      #
-      # Becomes:
-      #
-      #   generators/rails/model/model_generator.rb
-      #   generators/rails/model_generator.rb
-      #   generators/model_generator.rb
-      #
-      attempts.each do |attempt|
-        paths = attempt.gsub(':generators:', ':').split(':')
-        paths << "#{paths.last}_generator.rb"
-
-        until paths.empty?
-          generators_path << File.join(*paths)
-          paths.delete_at(-1) unless paths.delete_at(-2)
-        end
-      end
-
-      generators_path.uniq!
-      generators_path.each do |generator_path|
-        self.load_path.each do |path|
-          Dir[File.join(path, generator_path)].each do |file|
-            require file
-          end
-        end
-      end
-    end
-
     # Keep builtin generators in an Array[Array[group, name]].
     #
     def self.builtin
@@ -114,11 +77,15 @@ def self.find_by_namespace(name, base=nil, context=nil)
       attempts << name.sub(':', ':generators:') if name.count(':') == 1
       attempts << name
 
-      unless klass = find_many_by_namespace(attempts)
-        lookup(attempts)
-        klass = find_many_by_namespace(attempts)
+      unloaded = attempts - namespaces
+      lookup(unloaded)
+
+      attempts.each do |namespace|
+        klass = Thor::Util.find_by_namespace(namespace)
+        return klass if klass
       end
-      klass
+
+      nil
     end
 
     # Show help message with available generators.
@@ -133,8 +100,23 @@ def self.help
       puts "Please select a generator."
       puts "Builtin: #{rails.join(', ')}."
 
-      # TODO Show others after lookup is implemented
-      # puts "Others: #{others.join(', ')}."
+      # Load paths and remove builtin
+      paths, others = load_path.dup, []
+      paths.shift
+
+      paths.each do |path|
+        tail = [ "*", "*", "*_generator.rb" ]
+
+        until tail.empty?
+          others += Dir[File.join(path, *tail)].collect do |file|
+            file.split('/')[-tail.size, 2].join(':').sub(/_generator\.rb$/, '')
+          end
+          tail.shift
+        end
+      end
+
+      others.sort!
+      puts "Others: #{others.join(', ')}." unless others.empty?
     end
 
     # Receives a namespace, arguments and the behavior to invoke the generator.
@@ -152,12 +134,45 @@ def self.invoke(namespace, args=ARGV, behavior=:invoke)
 
     protected
 
-      def self.find_many_by_namespace(attempts)
-        attempts.each do |namespace|
-          klass = Thor::Util.find_by_namespace(namespace)
-          return klass if klass
+      # Return all defined namespaces.
+      #
+      def self.namespaces
+        Thor::Base.subclasses.map(&:namespace)
+      end
+
+      # Receives namespaces in an array and tries to find matching generators
+      # in the load path. Each path is traversed into directory lookups. For
+      # example:
+      #
+      #   rails:generators:model
+      #
+      # Becomes:
+      #
+      #   generators/rails/model/model_generator.rb
+      #   generators/rails/model_generator.rb
+      #   generators/model_generator.rb
+      #
+      def self.lookup(attempts)
+        attempts.each do |attempt|
+          generators_path = ['.']
+
+          paths = attempt.gsub(':generators:', ':').split(':')
+          name  = "#{paths.last}_generator.rb"
+
+          until paths.empty?
+            generators_path.unshift File.join(*paths)
+            paths.pop
+          end
+
+          generators_path.uniq!
+          generators_path = "{#{generators_path.join(',')}}"
+
+          self.load_path.each do |path|
+            Dir[File.join(path, generators_path, name)].each do |file|
+              require file
+            end
+          end
         end
-        nil
       end
 
   end
diff --git a/railties/test/fixtures/lib/generators/active_record/fixjour/fixjour_generator.rb b/railties/test/fixtures/lib/generators/active_record/fixjour/fixjour_generator.rb
new file mode 100644
index 0000000000000000000000000000000000000000..7a4edb8bcbc35414e212f9c329dd956aab8fbdb4
--- /dev/null
+++ b/railties/test/fixtures/lib/generators/active_record/fixjour/fixjour_generator.rb
@@ -0,0 +1,8 @@
+require 'generators/active_record'
+
+module ActiveRecord
+  module Generators
+    class FixjourGenerator < Base
+    end
+  end
+end
diff --git a/railties/test/fixtures/lib/generators/fixjour_generator.rb b/railties/test/fixtures/lib/generators/fixjour_generator.rb
new file mode 100644
index 0000000000000000000000000000000000000000..ef3e9edbed9b8731958cfc973a47bc9fc067fa26
--- /dev/null
+++ b/railties/test/fixtures/lib/generators/fixjour_generator.rb
@@ -0,0 +1,2 @@
+class FixjourGenerator < Rails::Generators::NamedBase
+end
diff --git a/railties/test/fixtures/lib/generators/missing_class/missing_class_generator.rb b/railties/test/fixtures/lib/generators/missing_class/missing_class_generator.rb
deleted file mode 100644
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..0000000000000000000000000000000000000000
diff --git a/railties/test/fixtures/lib/generators/missing_class/templates/.gitignore b/railties/test/fixtures/lib/generators/missing_class/templates/.gitignore
deleted file mode 100644
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..0000000000000000000000000000000000000000
diff --git a/railties/test/fixtures/lib/generators/missing_generator/templates/.gitignore b/railties/test/fixtures/lib/generators/missing_generator/templates/.gitignore
deleted file mode 100644
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..0000000000000000000000000000000000000000
diff --git a/railties/test/fixtures/lib/generators/missing_templates/.gitignore b/railties/test/fixtures/lib/generators/missing_templates/.gitignore
deleted file mode 100644
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..0000000000000000000000000000000000000000
diff --git a/railties/test/fixtures/lib/generators/rails/javascripts_generator.rb b/railties/test/fixtures/lib/generators/rails/javascripts_generator.rb
new file mode 100644
index 0000000000000000000000000000000000000000..cad5e9678483c24b80fc5771c187487bf58e8fbb
--- /dev/null
+++ b/railties/test/fixtures/lib/generators/rails/javascripts_generator.rb
@@ -0,0 +1,4 @@
+module Rails::Generators
+  class JavascriptsGenerator < Rails::Generators::NamedBase
+  end
+end
diff --git a/railties/test/fixtures/lib/generators/working/working_generator.rb b/railties/test/fixtures/lib/generators/working/working_generator.rb
deleted file mode 100644
index 465b34319ae13d55f6d9a7937a86be477204e210..0000000000000000000000000000000000000000
--- a/railties/test/fixtures/lib/generators/working/working_generator.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-class WorkingGenerator < Rails::Generator::NamedBase
-end
diff --git a/railties/test/generators/generators_test_helper.rb b/railties/test/generators/generators_test_helper.rb
index 7f22197a5476df948ecea8003311aa5ad87f84d7..2ccedf814d48c5bd64959e6dcf2b6772975652a3 100644
--- a/railties/test/generators/generators_test_helper.rb
+++ b/railties/test/generators/generators_test_helper.rb
@@ -1,9 +1,6 @@
 require 'test/unit'
 require 'fileutils'
 
-$LOAD_PATH.unshift "#{File.dirname(__FILE__)}/../../lib"
-require 'generators'
-
 fixtures = File.expand_path(File.join(File.dirname(__FILE__), '..', 'fixtures'))
 if defined?(RAILS_ROOT)
   RAILS_ROOT.replace fixtures
@@ -11,6 +8,9 @@
   RAILS_ROOT = fixtures
 end
 
+$LOAD_PATH.unshift "#{File.dirname(__FILE__)}/../../lib"
+require 'generators'
+
 class GeneratorsTestCase < Test::Unit::TestCase
   include FileUtils
 
diff --git a/railties/test/generators/model_generator_test.rb b/railties/test/generators/model_generator_test.rb
index d076244abd0cd4e3fe34add110a5c8c0a7f8a1a8..30fc83783483938956d47f8371cf942fce2ae526 100644
--- a/railties/test/generators/model_generator_test.rb
+++ b/railties/test/generators/model_generator_test.rb
@@ -107,8 +107,8 @@ def test_fixture_is_skipped
   end
 
   def test_fixture_is_skipped_if_fixture_replacement_is_given
-    content = run_generator ["account", "-r", "fixjour"]
-    assert_match /Could not find and invoke 'fixjour'/, content
+    content = run_generator ["account", "-r", "factory_girl"]
+    assert_match /Could not find and invoke 'factory_girl'/, content
     assert_no_file "test/fixtures/accounts.yml"
   end
 
diff --git a/railties/test/generators_test.rb b/railties/test/generators_test.rb
new file mode 100644
index 0000000000000000000000000000000000000000..ac290b10bb2801e5e2aa2ab391355810c9b1f51e
--- /dev/null
+++ b/railties/test/generators_test.rb
@@ -0,0 +1,80 @@
+require File.join(File.dirname(__FILE__), 'generators', 'generators_test_helper')
+require 'generators/rails/model/model_generator'
+require 'mocha'
+
+class GeneratorsTest < GeneratorsTestCase
+  def test_invoke_when_generator_is_not_found
+    output = capture(:stdout){ Rails::Generators.invoke :unknown }
+    assert_equal "Could not find generator unknown.\n", output
+  end
+
+  def test_help_when_a_generator_with_required_arguments_is_invoked_without_arguments
+    output = capture(:stdout){ Rails::Generators.invoke :model, [] }
+    assert_match /Description:/, output
+  end
+
+  def test_invoke_with_default_behavior
+    Rails::Generators::ModelGenerator.expects(:start).with(["Account"], :behavior => :invoke)
+    Rails::Generators.invoke :model, ["Account"]
+  end
+
+  def test_invoke_with_given_behavior
+    Rails::Generators::ModelGenerator.expects(:start).with(["Account"], :behavior => :skip)
+    Rails::Generators.invoke :model, ["Account"], :skip
+  end
+
+  def test_find_by_namespace_without_base_or_context
+    assert_nil Rails::Generators.find_by_namespace(:model)
+  end
+
+  def test_find_by_namespace_with_base
+    klass = Rails::Generators.find_by_namespace(:model, :rails)
+    assert klass
+    assert_equal "rails:generators:model", klass.namespace
+  end
+
+  def test_find_by_namespace_with_context
+    klass = Rails::Generators.find_by_namespace(:test_unit, nil, :model)
+    assert klass
+    assert_equal "test_unit:generators:model", klass.namespace
+  end
+
+  def test_find_by_namespace_add_generators_to_raw_lookups
+    klass = Rails::Generators.find_by_namespace("test_unit:model")
+    assert klass
+    assert_equal "test_unit:generators:model", klass.namespace
+  end
+
+  def test_find_by_namespace_lookup_to_the_rails_root_folder
+    klass = Rails::Generators.find_by_namespace(:fixjour)
+    assert klass
+    assert_equal "fixjour", klass.namespace
+  end
+
+  def test_find_by_namespace_lookup_to_deep_rails_root_folders
+    klass = Rails::Generators.find_by_namespace(:fixjour, :active_record)
+    assert klass
+    assert_equal "active_record:generators:fixjour", klass.namespace
+  end
+
+  def test_find_by_namespace_lookup_traverse_folders
+    klass = Rails::Generators.find_by_namespace(:javascripts, :rails)
+    assert klass
+    assert_equal "rails:generators:javascripts", klass.namespace
+  end
+
+  def test_builtin_generators
+    assert Rails::Generators.builtin.include? %w(rails model)
+  end
+
+  def test_rails_generators_help_with_builtin_information
+    output = capture(:stdout){ Rails::Generators.help }
+    assert_match /model/, output
+    assert_match /scaffold_controller/, output
+  end
+
+  def test_rails_generators_with_others_information
+    output = capture(:stdout){ Rails::Generators.help }.split("\n").last
+    assert_equal "Others: active_record:fixjour, fixjour, rails:javascripts.", output
+  end
+end