Use `Minitest::Result` for retain test result

Runnable.marshal_dump/load was removed in
https://github.com/seattlerb/minitest/commit/00433fc0a4fdd0e6b302aace633384ba1312237

Instead, `Minitest::Result` is contained test result and the that can be
marshalled.

1 files changed, 4 insertions, 2 deletions

diff --git a/activesupport/lib/active_support/testing/isolation.rb b/activesupport/lib/active_support/testing/isolation.rb
index fa9bebb181..562f985f1b 100644
--- a/activesupport/lib/active_support/testing/isolation.rb
+++ b/activesupport/lib/active_support/testing/isolation.rb
@@ -45,7 +45,8 @@ module ActiveSupport
                   end
                 }
               end
-              result = Marshal.dump(dup)
+              test_result = defined?(Minitest::Result) ? Minitest::Result.from(self) : dup
+              result = Marshal.dump(test_result)
             end
 
             write.puts [result].pack("m")
@@ -69,8 +70,9 @@ module ActiveSupport
 
           if ENV["ISOLATION_TEST"]
             yield
+            test_result = defined?(Minitest::Result) ? Minitest::Result.from(self) : dup
             File.open(ENV["ISOLATION_OUTPUT"], "w") do |file|
-              file.puts [Marshal.dump(dup)].pack("m")
+              file.puts [Marshal.dump(test_result)].pack("m")
             end
             exit!
           else