2 files changed, 47 insertions, 2 deletions

diff --git a/activesupport/lib/active_support/hash_with_indifferent_access.rb b/activesupport/lib/active_support/hash_with_indifferent_access.rb
index 4f71f13971..63690a1342 100644
--- a/activesupport/lib/active_support/hash_with_indifferent_access.rb
+++ b/activesupport/lib/active_support/hash_with_indifferent_access.rb
@@ -188,7 +188,7 @@ module ActiveSupport
     #   dup[:a][:c]  # => "c"
     def dup
       self.class.new(self).tap do |new_hash|
-        new_hash.default = default
+        set_defaults(new_hash)
       end
     end
 
@@ -247,7 +247,9 @@ module ActiveSupport
 
     # Convert to a regular hash with string keys.
     def to_hash
-      _new_hash = Hash.new(default)
+      _new_hash = Hash.new
+      set_defaults(_new_hash)
+
       each do |key, value|
         _new_hash[key] = convert_value(value, for: :to_hash)
       end
@@ -275,6 +277,14 @@ module ActiveSupport
           value
         end
       end
+
+      def set_defaults(target)
+        if default_proc
+          target.default_proc = default_proc.dup
+        else
+          target.default = default
+        end
+      end
   end
 end
 
diff --git a/activesupport/lib/active_support/testing/method_call_assertions.rb b/activesupport/lib/active_support/testing/method_call_assertions.rb
new file mode 100644
index 0000000000..e3cbe40308
--- /dev/null
+++ b/activesupport/lib/active_support/testing/method_call_assertions.rb
@@ -0,0 +1,35 @@
+module ActiveSupport
+  module Testing
+    module MethodCallAssertions # :nodoc:
+      private
+        def assert_called(object, method_name, message = nil, times: 1)
+          times_called = 0
+
+          object.stub(method_name, -> { times_called += 1 }) { yield }
+
+          error = "Expected #{method_name} to be called #{times} times, " \
+            "but was called #{times_called} times"
+          error = "#{message}.\n#{error}" if message
+          assert_equal times, times_called, error
+        end
+
+        def assert_called_with(object, method_name, args = [], returns: nil)
+          mock = Minitest::Mock.new
+
+          if args.all? { |arg| arg.is_a?(Array) }
+            args.each { |arg| mock.expect(:call, returns, arg) }
+          else
+            mock.expect(:call, returns, args)
+          end
+
+          object.stub(method_name, mock) { yield }
+
+          mock.verify
+        end
+
+        def assert_not_called(object, method_name, message = nil, &block)
+          assert_called(object, method_name, message, times: 0, &block)
+        end
+    end
+  end
+end
\ No newline at end of file