1 files changed, 15 insertions, 0 deletions
diff --git a/actionpack/test/controller/parameters/parameters_permit_test.rb b/actionpack/test/controller/parameters/parameters_permit_test.rb
index 437da43d9b..b60c5f058d 100644
--- a/actionpack/test/controller/parameters/parameters_permit_test.rb
+++ b/actionpack/test/controller/parameters/parameters_permit_test.rb
@@ -107,6 +107,15 @@ class ParametersPermitTest < ActiveSupport::TestCase
     assert_equal [], permitted[:id]
   end
 
+  test 'do not break params filtering on nil values' do
+    params = ActionController::Parameters.new(a: 1, b: [1, 2, 3], c: nil)
+
+    permitted = params.permit(:a, c: [], b: [])
+    assert_equal 1, permitted[:a]
+    assert_equal [1, 2, 3], permitted[:b]
+    assert_equal nil, permitted[:c]
+  end
+
   test 'key to empty array: arrays of permitted scalars pass' do
     [['foo'], [1], ['foo', 'bar'], [1, 2, 3]].each do |array|
       params = ActionController::Parameters.new(id: array)
@@ -138,6 +147,12 @@ class ParametersPermitTest < ActiveSupport::TestCase
     assert_equal :foo, e.param
   end
 
+  test "fetch with a default value of a hash does not mutate the object" do
+    params = ActionController::Parameters.new({})
+    params.fetch :foo, {}
+    assert_equal nil, params[:foo]
+  end
+
   test "fetch doesnt raise ParameterMissing exception if there is a default" do
     assert_equal "monkey", @params.fetch(:foo, "monkey")
     assert_equal "monkey", @params.fetch(:foo) { "monkey" }