unittests: use mock.patch.dict to deal with os.environ

3 files changed, 7 insertions, 12 deletions

diff --git a/unittests/allplatformstests.py b/unittests/allplatformstests.py
index e790ca493..dac7f9797 100644
--- a/unittests/allplatformstests.py
+++ b/unittests/allplatformstests.py
@@ -1055,6 +1055,7 @@ class AllPlatformTests(BasePlatformTests):
         # target internal dependency wrong include_directories: source dir
         self.assertPathBasenameEqual(incs[8], 'sub2')
 
+    @mock.patch.dict(os.environ)
     def test_compiler_detection(self):
         '''
         Test that automatic compiler detection and setting from the environment
diff --git a/unittests/baseplatformtests.py b/unittests/baseplatformtests.py
index 7ba2aaed4..ae012dada 100644
--- a/unittests/baseplatformtests.py
+++ b/unittests/baseplatformtests.py
@@ -42,6 +42,7 @@ from run_tests import (
 # e.g. for assertXXX helpers.
 __unittest = True
 
+@mock.patch.dict(os.environ)
 class BasePlatformTests(TestCase):
     prefix = '/usr'
     libdir = 'lib'
@@ -81,7 +82,6 @@ class BasePlatformTests(TestCase):
         self.darwin_test_dir = os.path.join(src_root, 'test cases/darwin')
 
         # Misc stuff
-        self.orig_env = os.environ.copy()
         if self.backend is Backend.ninja:
             self.no_rebuild_stdout = ['ninja: no work to do.', 'samu: nothing to do']
         else:
@@ -147,8 +147,6 @@ class BasePlatformTests(TestCase):
                 windows_proof_rmtree(path)
             except FileNotFoundError:
                 pass
-        os.environ.clear()
-        os.environ.update(self.orig_env)
         super().tearDown()
 
     def _run(self, command, *, workdir=None, override_envvars: T.Optional[T.Mapping[str, str]] = None, stderr=True):
diff --git a/unittests/helpers.py b/unittests/helpers.py
index 2f97ab1d4..5cf8845b2 100644
--- a/unittests/helpers.py
+++ b/unittests/helpers.py
@@ -12,6 +12,7 @@ import typing as T
 import zipfile
 from pathlib import Path
 from contextlib import contextmanager
+from unittest import mock
 
 from mesonbuild.compilers import detect_c_compiler, compiler_from_language
 from mesonbuild.mesonlib import (
@@ -119,16 +120,11 @@ def skip_if_env_set(key: str) -> T.Callable[[T.Callable[P, R]], T.Callable[P, R]
     def wrapper(func: T.Callable[P, R]) -> T.Callable[P, R]:
         @functools.wraps(func)
         def wrapped(*args: P.args, **kwargs: P.kwargs) -> R:
-            old = None
-            if key in os.environ:
-                if not is_ci():
-                    raise unittest.SkipTest(f'Env var {key!r} set, skipping')
-                old = os.environ.pop(key)
-            try:
+            if key in os.environ and not is_ci():
+                raise unittest.SkipTest(f'Env var {key!r} set, skipping')
+            with mock.patch.dict(os.environ):
+                os.environ.pop(key, None)
                 return func(*args, **kwargs)
-            finally:
-                if old is not None:
-                    os.environ[key] = old
         return wrapped
     return wrapper