2 files changed, 13 insertions, 5 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/controller/parameters/parameters_permit_test.rb b/actionpack/test/controller/parameters/parameters_permit_test.rb
index 295f3a03ef..e60003dc64 100644
--- a/actionpack/test/controller/parameters/parameters_permit_test.rb
+++ b/actionpack/test/controller/parameters/parameters_permit_test.rb
@@ -309,7 +309,7 @@ class ParametersPermitTest < ActiveSupport::TestCase
     merged_params = @params.reverse_merge(default_params)
 
     assert_equal "1234", merged_params[:id]
-    refute_predicate merged_params[:person], :empty?
+    assert_not_predicate merged_params[:person], :empty?
   end
 
   test "#with_defaults is an alias of reverse_merge" do
@@ -317,11 +317,11 @@ class ParametersPermitTest < ActiveSupport::TestCase
     merged_params = @params.with_defaults(default_params)
 
     assert_equal "1234", merged_params[:id]
-    refute_predicate merged_params[:person], :empty?
+    assert_not_predicate merged_params[:person], :empty?
   end
 
   test "not permitted is sticky beyond reverse_merge" do
-    refute_predicate @params.reverse_merge(a: "b"), :permitted?
+    assert_not_predicate @params.reverse_merge(a: "b"), :permitted?
   end
 
   test "permitted is sticky beyond reverse_merge" do
@@ -334,7 +334,7 @@ class ParametersPermitTest < ActiveSupport::TestCase
     @params.reverse_merge!(default_params)
 
     assert_equal "1234", @params[:id]
-    refute_predicate @params[:person], :empty?
+    assert_not_predicate @params[:person], :empty?
   end
 
   test "#with_defaults! is an alias of reverse_merge!" do
@@ -342,7 +342,7 @@ class ParametersPermitTest < ActiveSupport::TestCase
     @params.with_defaults!(default_params)
 
     assert_equal "1234", @params[:id]
-    refute_predicate @params[:person], :empty?
+    assert_not_predicate @params[:person], :empty?
   end
 
   test "modifying the parameters" do