From 0515e4e0f144f593b3a9150d009dc1ad5c39c184 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sandro=20J=C3=A4ckel?= <sandro.jaeckel@gmail.com>
Date: Mon, 22 Jun 2026 17:08:31 +0200
Subject: [PATCH] python314Packages.xarray: add pytest-xdist to speed up tests
 by 2x

---
 pkgs/development/python-modules/xarray/default.nix | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/pkgs/development/python-modules/xarray/default.nix b/pkgs/development/python-modules/xarray/default.nix
index 6bc6e731ce2b..b0e9e537cd56 100644
--- a/pkgs/development/python-modules/xarray/default.nix
+++ b/pkgs/development/python-modules/xarray/default.nix
@@ -7,7 +7,7 @@
   setuptools,
   setuptools-scm,
 
-  # dependenices
+  # dependencies
   numpy,
   packaging,
   pandas,
@@ -32,6 +32,7 @@
 
   # tests
   pytest-asyncio,
+  pytest-xdist,
   pytestCheckHook,
   h5py,
 }:
@@ -98,8 +99,14 @@ buildPythonPackage (finalAttrs: {
       accel ++ io ++ etc ++ parallel ++ viz;
   };
 
+  preCheck = ''
+    # tests become flaky with to many cores
+    export NIX_BUILD_CORES=$((NIX_BUILD_CORES > 8 ? 8 : NIX_BUILD_CORES))
+  '';
+
   nativeCheckInputs = [
     pytest-asyncio
+    pytest-xdist
     pytestCheckHook
   ]
   # Besides scipy, these are not strictly needed for the tests, but adding all