3 files changed, 113 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/test_case.rb b/activesupport/lib/active_support/test_case.rb
index d2b8e602f9..60bd4ace9b 100644
--- a/activesupport/lib/active_support/test_case.rb
+++ b/activesupport/lib/active_support/test_case.rb
@@ -5,6 +5,7 @@ require 'active_support/testing/assertions'
 require 'active_support/testing/deprecation'
 require 'active_support/testing/isolation'
 require 'active_support/testing/mocha_module'
+require 'active_support/testing/constant_lookup'
 require 'active_support/core_ext/kernel/reporting'
 require 'active_support/deprecation'
 
@@ -35,6 +36,7 @@ module ActiveSupport
     include ActiveSupport::Testing::SetupAndTeardown
     include ActiveSupport::Testing::Assertions
     include ActiveSupport::Testing::Deprecation
+    include ActiveSupport::Testing::ConstantLookup
 
     def self.describe(text)
       if block_given?
diff --git a/activesupport/lib/active_support/testing/constant_lookup.rb b/activesupport/lib/active_support/testing/constant_lookup.rb
new file mode 100644
index 0000000000..8cb84b3f20
--- /dev/null
+++ b/activesupport/lib/active_support/testing/constant_lookup.rb
@@ -0,0 +1,53 @@
+require "active_support/concern"
+
+module ActiveSupport
+  module Testing
+    # Resolves a constant from a minitest spec name.
+    #
+    # Given the following spec-style test:
+    #
+    #   describe WidgetsController, :index do
+    #     describe "authenticated user" do
+    #       describe "returns widgets" do
+    #         it "has a controller that exists" do
+    #           assert_kind_of WidgetsController, @controller
+    #         end
+    #       end
+    #     end
+    #   end
+    #
+    # The test will have the following name:
+    #
+    #   "WidgetsController::index::authenticated user::returns widgets"
+    #
+    # The constant WidgetsController can be resolved from the name.
+    # The following code will resolve the constant:
+    #
+    #   controller = determine_constant_from_test_name(name) do |constant|
+    #     Class === constant && constant < ::ActionController::Metal
+    #   end
+    module ConstantLookup
+      extend ::ActiveSupport::Concern
+
+      module ClassMethods
+        def determine_constant_from_test_name(test_name)
+          names = test_name.split "::"
+          while names.size > 0 do
+            names.last.sub! /Test$/, ""
+            # Rails 3.0 doesn't have safe_constantize,
+            # so we'll do it the hard way.
+            begin
+              constant = names.join("::").constantize
+              break(constant) if yield(constant)
+            rescue NameError
+              # Constant wasn't found, move on
+            ensure
+              names.pop
+            end
+          end
+        end
+      end
+
+    end
+  end
+end
diff --git a/activesupport/test/testing/constant_lookup_test.rb b/activesupport/test/testing/constant_lookup_test.rb
new file mode 100644
index 0000000000..f39d38e5cd
--- /dev/null
+++ b/activesupport/test/testing/constant_lookup_test.rb
@@ -0,0 +1,58 @@
+require 'abstract_unit'
+
+class Foo; end
+class Bar < Foo;
+  def index; end
+  def self.index; end
+end
+class Baz < Bar; end
+module FooBar; end
+
+class TestLookup < ActiveSupport::TestCase
+
+  def find_foo(name)
+    self.class.determine_constant_from_test_name(name) do |constant|
+      Class === constant && constant < Foo
+    end
+  end
+
+  def find_module(name)
+    self.class.determine_constant_from_test_name(name) do |constant|
+      Module === constant
+    end
+  end
+
+  def test_find_bar_from_foo
+    assert_equal Bar, find_foo("Bar")
+    assert_equal Bar, find_foo("Bar::index")
+    assert_equal Bar, find_foo("Bar::index::authenticated")
+    assert_equal Bar, find_foo("BarTest")
+    assert_equal Bar, find_foo("BarTest::index")
+    assert_equal Bar, find_foo("BarTest::index::authenticated")
+  end
+
+  def test_find_module
+    assert_equal FooBar, find_module("FooBar")
+    assert_equal FooBar, find_module("FooBar::index")
+    assert_equal FooBar, find_module("FooBar::index::authenticated")
+    assert_equal FooBar, find_module("FooBarTest")
+    assert_equal FooBar, find_module("FooBarTest::index")
+    assert_equal FooBar, find_module("FooBarTest::index::authenticated")
+  end
+
+  def test_returns_nil_when_cant_find_foo
+    assert_nil find_foo("DoesntExist")
+    assert_nil find_foo("DoesntExistTest")
+    assert_nil find_foo("DoesntExist::Nadda")
+    assert_nil find_foo("DoesntExist::Nadda::Nope")
+    assert_nil find_foo("DoesntExist::Nadda::Nope::NotHere")
+  end
+
+  def test_returns_nil_when_cant_find_module
+    assert_nil find_module("DoesntExist")
+    assert_nil find_module("DoesntExistTest")
+    assert_nil find_module("DoesntExist::Nadda")
+    assert_nil find_module("DoesntExist::Nadda::Nope")
+    assert_nil find_module("DoesntExist::Nadda::Nope::NotHere")
+  end
+end