2 files changed, 20 insertions, 0 deletions
diff --git a/actionpack/test/controller/parameters/accessors_test.rb b/actionpack/test/controller/parameters/accessors_test.rb
index 07a897a103..674b2c6266 100644
--- a/actionpack/test/controller/parameters/accessors_test.rb
+++ b/actionpack/test/controller/parameters/accessors_test.rb
@@ -284,4 +284,12 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
       value.is_a?(ActionController::Parameters)
     end
   end
+
+  test "mutating #dig return value mutates underlying parameters" do
+    @params.dig(:person, :name)[:first] = "Bill"
+    assert_equal "Bill", @params.dig(:person, :name, :first)
+
+    @params.dig(:person, :addresses)[0] = { city: "Boston", state: "Massachusetts" }
+    assert_equal "Boston", @params.dig(:person, :addresses, 0, :city)
+  end
 end
diff --git a/actionpack/test/dispatch/request/session_test.rb b/actionpack/test/dispatch/request/session_test.rb
index bf5a74e694..74da2fe7d3 100644
--- a/actionpack/test/dispatch/request/session_test.rb
+++ b/actionpack/test/dispatch/request/session_test.rb
@@ -118,6 +118,18 @@ module ActionDispatch
         end
       end
 
+      def test_dig
+        session = Session.create(store, req, {})
+        session["one"] = { "two" => "3" }
+
+        assert_equal "3", session.dig("one", "two")
+        assert_equal "3", session.dig(:one, "two")
+
+        assert_nil session.dig("three", "two")
+        assert_nil session.dig("one", "three")
+        assert_nil session.dig("one", :two)
+      end
+
       private
         def store
           Class.new {