diff --git a/activesupport/test/core_ext/array/conversions_test.rb b/activesupport/test/core_ext/array/conversions_test.rb
index 51ad9897dac..577b889410e 100644
--- a/activesupport/test/core_ext/array/conversions_test.rb
+++ b/activesupport/test/core_ext/array/conversions_test.rb
@@ -52,6 +52,14 @@ class ToSentenceTest < ActiveSupport::TestCase
   def test_with_blank_elements
     assert_equal ", one, , two, and three", [nil, 'one', '', 'two', 'three'].to_sentence
   end
+
+  def test_with_invalid_options
+    exception = assert_raise ArgumentError do
+      ['one', 'two'].to_sentence(passing: 'invalid option')
+    end
+
+    assert_equal exception.message, "Unknown key: :passing. Valid keys are: :words_connector, :two_words_connector, :last_word_connector, :locale"
+  end
 end
 
 class ToSTest < ActiveSupport::TestCase
@@ -187,25 +195,3 @@ class ToXmlTest < ActiveSupport::TestCase
     assert_equal({ skip_instruct: true }, options)
   end
 end
-
-class ToParamTest < ActiveSupport::TestCase
-  class ToParam < String
-    def to_param
-      "#{self}1"
-    end
-  end
-
-  def test_string_array
-    assert_equal '', %w().to_param
-    assert_equal 'hello/world', %w(hello world).to_param
-    assert_equal 'hello/10', %w(hello 10).to_param
-  end
-
-  def test_number_array
-    assert_equal '10/20', [10, 20].to_param
-  end
-
-  def test_to_param_array
-    assert_equal 'custom1/param1', [ToParam.new('custom'), ToParam.new('param')].to_param
-  end
-end
diff --git a/activesupport/test/core_ext/object/to_param_test.rb b/activesupport/test/core_ext/object/to_param_test.rb
index 25c3bf22c33..30a7557dc2d 100644
--- a/activesupport/test/core_ext/object/to_param_test.rb
+++ b/activesupport/test/core_ext/object/to_param_test.rb
@@ -2,6 +2,12 @@ require 'abstract_unit'
 require 'active_support/core_ext/object/to_param'
 
 class ToParamTest < ActiveSupport::TestCase
+  class CustomString < String
+    def to_param
+      "custom-#{ self }"
+    end
+  end
+
   def test_object
     foo = Object.new
     def foo.to_s; 'foo' end
@@ -25,7 +31,7 @@ class ToParamTest < ActiveSupport::TestCase
     assert_equal "1/2/3/4", array.to_param
 
     # Array of different objects
-    array = [1, '3', { a: 1, b: 2 }, nil, true, false]
-    assert_equal "1/3/a=1&b=2//true/false", array.to_param
+    array = [1, '3', { a: 1, b: 2 }, nil, true, false, CustomString.new('object')]
+    assert_equal "1/3/a=1&b=2//true/false/custom-object", array.to_param
   end
 end