add more testcases and doc about Hash#extract!

1 files changed, 10 insertions, 2 deletions

diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md
index 2a84242b9c..53f0579b0f 100644
--- a/guides/source/active_support_core_extensions.md
+++ b/guides/source/active_support_core_extensions.md
@@ -2867,8 +2867,16 @@ The method `extract!` removes and returns the key/value pairs matching the given
 
 ```ruby
 hash = {:a => 1, :b => 2}
-rest = hash.extract!(:a) # => {:a => 1}
-hash                     # => {:b => 2}
+rest = hash.extract!(:a, :x) # => {:a => 1}     # non-existing keys are ignored
+hash                         # => {:b => 2}
+```
+
+The method `extract!` returns the same subclass of Hash, that the receiver is.
+
+```ruby
+hash = {:a => 1, :b => 2}.with_indifferent_access
+rest = hash.extract!(:a).class
+# => ActiveSupport::HashWithIndifferentAccess
 ```
 
 NOTE: Defined in `active_support/core_ext/hash/slice.rb`.