--- flexmock-2.3.6/test/partial_mock_test.rb.workaround	2021-01-24 02:36:13.468840410 +0900
+++ flexmock-2.3.6/test/partial_mock_test.rb	2021-01-24 03:03:55.748278701 +0900
@@ -621,7 +621,8 @@
     exception = assert_raises(NameError) do
         obj.mocked_method
     end
-    assert_equal "undefined method `does_not_exist' for #{obj}", exception.message
+    assert(/undefined method `does_not_exist' for #<#<Class:/ === exception.message, 
+        "expected #{exception.message} to match /undefined method `does_not_exist' for #<#<Class:/")
   end
 
   def test_it_checks_whether_mocks_are_forbidden_before_forwarding_the_call