From 6c952ac600e41eeea6fdeab510829ad42b053fe1 Mon Sep 17 00:00:00 2001
From: Jun Aruga <junaruga@users.noreply.github.com>
Date: Mon, 9 Oct 2023 17:05:51 +0200
Subject: [PATCH] testing_ruby.md: Document running test suites on s390x CPU
 architecture [ci skip] (#8589)

---
 doc/contributing/testing_ruby.md | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/doc/contributing/testing_ruby.md b/doc/contributing/testing_ruby.md
index 8decc24083..b8f3c004c9 100644
--- a/doc/contributing/testing_ruby.md
+++ b/doc/contributing/testing_ruby.md
@@ -142,3 +142,15 @@ We can run any of the make scripts [in parallel](building_ruby.md#label-Running+
     ```
     $ make test-bundler BUNDLER_SPECS=commands/exec_spec.rb
     ```
+
+## Troubleshooting
+
+### Running test suites on s390x CPU Architecture
+
+If we see failing tests related to the zlib library on s390x CPU architecture, we can run the test suites with `DFLTCC=0` to pass:
+
+```
+DFLTCC=0 make check
+```
+
+The failures can happen with the zlib library applying the patch [madler/zlib#410](https://github.com/madler/zlib/pull/410) to enable the deflate algorithm producing a different compressed byte stream. We manage this issue at [[ruby-core:114942][Bug #19909]](https://bugs.ruby-lang.org/issues/19909).