diff --git a/test/support/hash_with_indifferent_access.rb b/test/support/hash_with_indifferent_access.rb
index 498254d..e3d5caf 100644
--- a/test/support/hash_with_indifferent_access.rb
+++ b/test/support/hash_with_indifferent_access.rb
@@ -38,19 +38,6 @@ class Hash
 
   alias_method :to_options,  :symbolize_keys
   #alias_method :to_options!, :symbolize_keys!
-
-  # Validate all keys in a hash match *valid keys, raising ArgumentError on a mismatch.
-  # Note that keys are NOT treated indifferently, meaning if you use strings for keys but assert symbols
-  # as keys, this will fail.
-  #
-  # ==== Examples
-  #   { :name => "Rob", :years => "28" }.assert_valid_keys(:name, :age) # => raises "ArgumentError: Unknown key(s): years"
-  #   { :name => "Rob", :age => "28" }.assert_valid_keys("name", "age") # => raises "ArgumentError: Unknown key(s): name, age"
-  #   { :name => "Rob", :age => "28" }.assert_valid_keys(:name, :age) # => passes, raises nothing
-  def assert_valid_keys(*valid_keys)
-    unknown_keys = keys - [valid_keys].flatten
-    raise(ArgumentError, "Unknown key(s): #{unknown_keys.join(", ")}") unless unknown_keys.empty?
-  end
 end
 
 module ActiveSupport