From e95080f734c3247fa79187ac68ada1f5c92abe5f Mon Sep 17 00:00:00 2001
From: Tony Meyer <tony.meyer@canonical.com>
Date: Thu, 5 Sep 2024 13:55:53 +1200
Subject: [PATCH] fix: avoid changing os.environ in Harness.

---
 ops/testing.py | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/ops/testing.py b/ops/testing.py
index 40d60fc4f..9c4d7c9a1 100644
--- a/ops/testing.py
+++ b/ops/testing.py
@@ -260,9 +260,10 @@ def __init__(
         actions: Optional[YAMLStringOrFile] = None,
         config: Optional[YAMLStringOrFile] = None,
     ):
-        if 'JUJU_VERSION' not in os.environ:
-            os.environ['JUJU_VERSION'] = '0.0.0'
-        self._juju_context = _JujuContext.from_dict(os.environ)
+        context_environ = os.environ.copy()
+        if 'JUJU_VERSION' not in context_environ:
+            context_environ['JUJU_VERSION'] = '0.0.0'
+        self._juju_context = _JujuContext.from_dict(context_environ)
         self._charm_cls = charm_cls
         self._charm: Optional[CharmType] = None
         self._charm_dir = 'no-disk-path'  # this may be updated by _create_meta