3 files changed, 21 insertions, 0 deletions
diff --git a/activesupport/lib/core_ext.rb b/activesupport/lib/core_ext.rb
new file mode 100644
index 0000000000..d288fb7e31
--- /dev/null
+++ b/activesupport/lib/core_ext.rb
@@ -0,0 +1 @@
+Dir[File.dirname(__FILE__) + "/core_ext/*.rb"].each { |file| require(file) }
+\ No newline at end of file
diff --git a/activesupport/lib/core_ext/hash_ext.rb b/activesupport/lib/core_ext/hash_ext.rb
new file mode 100644
index 0000000000..90670c42c7
--- /dev/null
+++ b/activesupport/lib/core_ext/hash_ext.rb
@@ -0,0 +1,6 @@
+class Hash
+  def assert_valid_keys(valid_keys)
+    unknown_keys = keys - valid_keys
+    raise(ArgumentError, "Unknown key(s): #{unknown_keys.join(", ")}") unless unknown_keys.empty?
+  end
+end
+\ No newline at end of file
diff --git a/activesupport/test/core_ext/hash_ext_test.rb b/activesupport/test/core_ext/hash_ext_test.rb
new file mode 100644
index 0000000000..f481cf0242
--- /dev/null
+++ b/activesupport/test/core_ext/hash_ext_test.rb
@@ -0,0 +1,14 @@
+require 'test/unit'
+require File.dirname(__FILE__) + '/../../lib/core_ext/hash_ext'
+
+class HashExtTest < Test::Unit::TestCase
+  def test_assert_valid_keys
+    assert_nothing_raised do
+      { :failure => "stuff", :funny => "business" }.assert_valid_keys([ :failure, :funny ])
+    end
+    
+    assert_raises(ArgumentError, "Unknown key(s): failore") do
+      { :failore => "stuff", :funny => "business" }.assert_valid_keys([ :failure, :funny ])
+    end
+  end
+end
+\ No newline at end of file