diff --git a/.github/workflows/tests-macos.yml b/.github/workflows/tests-macos.yml
index 4d199c960..3adf3de38 100644
--- a/.github/workflows/tests-macos.yml
+++ b/.github/workflows/tests-macos.yml
@@ -13,6 +13,8 @@ concurrency:
 jobs:
   tests:
     runs-on: macos-latest
+    env:
+      PYTEST_ADDOPTS: -n auto
     strategy:
       fail-fast: false
       matrix:
diff --git a/.github/workflows/tests-ubuntu.yml b/.github/workflows/tests-ubuntu.yml
index 585cdd307..c07cd49f0 100644
--- a/.github/workflows/tests-ubuntu.yml
+++ b/.github/workflows/tests-ubuntu.yml
@@ -13,6 +13,8 @@ concurrency:
 jobs:
   tests:
     runs-on: ubuntu-latest
+    env:
+      PYTEST_ADDOPTS: -n auto
     strategy:
       fail-fast: false
       matrix:
diff --git a/.github/workflows/tests-windows.yml b/.github/workflows/tests-windows.yml
index 9b03b594d..48aa56e15 100644
--- a/.github/workflows/tests-windows.yml
+++ b/.github/workflows/tests-windows.yml
@@ -13,6 +13,8 @@ concurrency:
 jobs:
   tests:
     runs-on: windows-latest
+    env:
+      PYTEST_ADDOPTS: -n auto
     strategy:
       fail-fast: false
       matrix:
diff --git a/tests/test_pipeline_files.py b/tests/test_pipeline_files.py
index 6b63dc056..7f5060701 100644
--- a/tests/test_pipeline_files.py
+++ b/tests/test_pipeline_files.py
@@ -700,6 +700,10 @@ class TestFTPFileStore:
         meta = {"foo": "bar"}
         path = "full/filename"
         with MockFTPServer() as ftp_server:
+            # normally set via FilesPipeline.from_crawler()
+            FTPFilesStore.FTP_USERNAME = "anonymous"
+            FTPFilesStore.FTP_PASSWORD = "guest"
+
             store = FTPFilesStore(ftp_server.url("/"))
             empty_dict = yield store.stat_file(path, info=None)
             assert empty_dict == {}
diff --git a/tests/test_spider_start.py b/tests/test_spider_start.py
index 8ca588978..4e359fd33 100644
--- a/tests/test_spider_start.py
+++ b/tests/test_spider_start.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import re
 import warnings
 from asyncio import sleep
 from typing import Any
@@ -140,11 +141,16 @@ class TestMain:
                 for item_or_request in super().start_requests():
                     yield item_or_request
 
-        with pytest.warns(
-            ScrapyDeprecationWarning, match=r"use Spider\.start\(\) instead"
-        ) as messages:
+        msg = "use Spider.start() instead"
+        with pytest.warns(ScrapyDeprecationWarning, match=re.escape(msg)) as ws:
             await self._test_spider(TestSpider, [])
-        assert messages[0].filename.endswith("test_spider_start.py")
+
+        for w in ws:
+            if isinstance(w.message, ScrapyDeprecationWarning) and msg in str(
+                w.message
+            ):
+                assert w.filename.endswith("test_spider_start.py")
+                break
 
     async def _test_start(self, start_, expected_items=None):
         class TestSpider(Spider):
diff --git a/tox.ini b/tox.ini
index 3be564502..213ecbef6 100644
--- a/tox.ini
+++ b/tox.ini
@@ -26,6 +26,7 @@ deps =
     {[test-requirements]deps}
     pytest >= 8.4.1  # https://github.com/pytest-dev/pytest/pull/13502
 passenv =
+    PYTEST_ADDOPTS
     S3_TEST_FILE_URI
     AWS_ACCESS_KEY_ID
     AWS_SECRET_ACCESS_KEY