From da9ae24d6cfed4d05edc4d4c03ad9679307762b4 Mon Sep 17 00:00:00 2001
From: Katsuya HIDAKA <hidakatsuya@gmail.com>
Date: Tue, 2 Jun 2026 11:50:19 +0900
Subject: Enable parallel tests only in test workflow

---
 .github/workflows/tests.yml          | 3 +++
 doc/RUNNING_TESTS                    | 5 ++---
 test/application_system_test_case.rb | 2 --
 test/test_helper.rb                  | 2 +-
 4 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index ac1943d5e..8f6de5ed2 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -52,6 +52,9 @@ jobs:
           db-type: ${{ matrix.db }}
           ruby-version: ${{ matrix.ruby }}
 
+      - name: Enable parallel tests
+        run: echo "PARALLEL_WORKERS=$(nproc)" >> $GITHUB_ENV
+
       - name: Run tests
         run: |
           bin/rails test
diff --git a/doc/RUNNING_TESTS b/doc/RUNNING_TESTS
index 8f63b38b1..166a82f10 100644
--- a/doc/RUNNING_TESTS
+++ b/doc/RUNNING_TESTS
@@ -14,9 +14,8 @@ Apache perl module Redmine.pm and Capybara tests, see below).
 You can run `ruby test/unit/issue_test.rb` for running a single test case and
 `ruby test/unit/issue_test.rb -n test_create` for running a single test.
 
-Tests run in parallel by default, using the number of processors as the worker
-count. You can change the worker count by setting the PARALLEL_WORKERS
-environment variable:
+You can run tests in parallel by setting the PARALLEL_WORKERS environment
+variable:
 `PARALLEL_WORKERS=8 bin/rails test`
 
 Before running tests, you need to configure both development
diff --git a/test/application_system_test_case.rb b/test/application_system_test_case.rb
index 3deea4656..38d69e7c8 100644
--- a/test/application_system_test_case.rb
+++ b/test/application_system_test_case.rb
@@ -20,8 +20,6 @@
 require_relative 'test_helper'
 
 class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
-  parallelize(workers: 1)
-
   DOWNLOADS_PATH = File.expand_path(File.join(Rails.root, 'tmp', 'downloads'))
 
   # Allow running Capybara default server on custom IP address and/or port
diff --git a/test/test_helper.rb b/test/test_helper.rb
index ec3e20c94..9dd387a22 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -50,7 +50,7 @@ class ActionView::TestCase
 end
 
 class ActiveSupport::TestCase
-  parallelize(workers: :number_of_processors)
+  parallelize(workers: 1)
 
   include ActionDispatch::TestProcess
 
-- 
2.51.0