diff --git a/pex/commands/command.py b/pex/commands/command.py
index b32330237..32575acb6 100644
--- a/pex/commands/command.py
+++ b/pex/commands/command.py
@@ -17,7 +17,7 @@
 from pex import pex_warnings
 from pex.argparse import HandleBoolAction
 from pex.cache import access as cache_access
-from pex.common import safe_mkdtemp, safe_open
+from pex.common import environment_as, safe_mkdtemp, safe_open
 from pex.compatibility import shlex_quote
 from pex.result import Error, Ok, Result
 from pex.typing import TYPE_CHECKING, Generic, cast
@@ -379,7 +379,7 @@ def warn_ignore_pex_root(set_via):
             else:
                 pex_root = options.cache_dir or options.pex_root or ENV.PEX_ROOT
 
-            with ENV.patch(PEX_ROOT=pex_root, TMPDIR=tmpdir) as env:
+            with ENV.patch(PEX_ROOT=pex_root, TMPDIR=tmpdir) as env, environment_as(**env):
                 cache_access.read_write()
                 yield env
 
diff --git a/pex/common.py b/pex/common.py
index 1135dee9e..056ce6fbf 100644
--- a/pex/common.py
+++ b/pex/common.py
@@ -17,6 +17,7 @@
 import time
 import zipfile
 from collections import defaultdict, namedtuple
+from contextlib import contextmanager
 from datetime import datetime
 from uuid import uuid4
 from zipfile import ZipFile, ZipInfo
@@ -917,3 +918,28 @@ def iter_copytree(
         if copy_mode is CopyMode.SYMLINK:
             # Once we've symlinked the top-level directories and files, we've "copied" everything.
             return
+
+
+@contextmanager
+def environment_as(**kwargs):
+    # type: (**Any) -> Iterator[None]
+    """Mutates the `os.environ` for the duration of the context.
+
+    Keyword arguments with None values are removed from os.environ (if present) and all other
+    keyword arguments are added or updated in `os.environ` with the values taken from the
+    stringification (`str(...)`) of each value.
+    """
+    existing = {key: os.environ.get(key) for key in kwargs}
+
+    def adjust_environment(mapping):
+        for key, value in mapping.items():
+            if value is not None:
+                os.environ[key] = str(value)
+            else:
+                os.environ.pop(key, None)
+
+    adjust_environment(kwargs)
+    try:
+        yield
+    finally:
+        adjust_environment(existing)
diff --git a/pex/jobs.py b/pex/jobs.py
index 2fa1234f4..67513596b 100644
--- a/pex/jobs.py
+++ b/pex/jobs.py
@@ -17,7 +17,7 @@
 from pex.common import pluralize
 from pex.compatibility import Queue, cpu_count
 from pex.tracer import TRACER
-from pex.typing import TYPE_CHECKING, Generic, cast
+from pex.typing import TYPE_CHECKING, Generic
 
 if TYPE_CHECKING:
     from typing import (
@@ -679,12 +679,8 @@ def join(self):
 @contextmanager
 def _mp_pool(size):
     # type: (int) -> Iterator[Pool]
-    try:
-        context = multiprocessing.get_context("fork")  # type: ignore[attr-defined]
-        pool = cast("Pool", context.Pool(processes=size))
-    except (AttributeError, ValueError):
-        pool = multiprocessing.Pool(processes=size)
 
+    pool = multiprocessing.Pool(processes=size)
     try:
         yield pool
     finally:
diff --git a/testing/__init__.py b/testing/__init__.py
index 4e22f4d8a..b9be3f12a 100644
--- a/testing/__init__.py
+++ b/testing/__init__.py
@@ -674,25 +674,6 @@ def all_python_venvs(system_site_packages=False):
     )
 
 
-@contextmanager
-def environment_as(**kwargs):
-    # type: (**Any) -> Iterator[None]
-    existing = {key: os.environ.get(key) for key in kwargs}
-
-    def adjust_environment(mapping):
-        for key, value in mapping.items():
-            if value is not None:
-                os.environ[key] = str(value)
-            else:
-                os.environ.pop(key, None)
-
-    adjust_environment(kwargs)
-    try:
-        yield
-    finally:
-        adjust_environment(existing)
-
-
 @contextmanager
 def pushd(directory):
     # type: (Text) -> Iterator[None]
diff --git a/tests/integration/cli/commands/test_cache_prune.py b/tests/integration/cli/commands/test_cache_prune.py
index 4049c012a..788bd9624 100644
--- a/tests/integration/cli/commands/test_cache_prune.py
+++ b/tests/integration/cli/commands/test_cache_prune.py
@@ -27,13 +27,13 @@
     VenvDirs,
 )
 from pex.cli.commands.cache.du import DiskUsage
-from pex.common import safe_open
+from pex.common import environment_as, safe_open
 from pex.pep_503 import ProjectName
 from pex.pex_info import PexInfo
 from pex.pip.version import PipVersion, PipVersionValue
 from pex.typing import TYPE_CHECKING
 from pex.variables import ENV
-from testing import environment_as, run_pex_command
+from testing import run_pex_command
 from testing.cli import run_pex3
 from testing.pytest.tmp import Tempdir
 
diff --git a/tests/integration/test_integration.py b/tests/integration/test_integration.py
index bea301fe3..164763655 100644
--- a/tests/integration/test_integration.py
+++ b/tests/integration/test_integration.py
@@ -19,7 +19,15 @@
 
 from pex import targets
 from pex.cache.dirs import CacheDir, InterpreterDir
-from pex.common import is_exe, safe_mkdir, safe_open, safe_rmtree, temporary_dir, touch
+from pex.common import (
+    environment_as,
+    is_exe,
+    safe_mkdir,
+    safe_open,
+    safe_rmtree,
+    temporary_dir,
+    touch,
+)
 from pex.compatibility import WINDOWS, commonpath
 from pex.dist_metadata import Distribution, Requirement, is_wheel
 from pex.fetcher import URLFetcher
@@ -46,7 +54,6 @@
     IntegResults,
     built_wheel,
     ensure_python_interpreter,
-    environment_as,
     get_dep_dist_names_from_pex,
     make_env,
     run_pex_command,
diff --git a/tests/integration/test_issue_157.py b/tests/integration/test_issue_157.py
index f9548ace9..9e17a677d 100644
--- a/tests/integration/test_issue_157.py
+++ b/tests/integration/test_issue_157.py
@@ -14,10 +14,11 @@
 import pytest
 from colors import color  # vendor:skip
 
+from pex.common import environment_as
 from pex.pex_info import PexInfo
 from pex.typing import TYPE_CHECKING
 from pex.version import __version__
-from testing import IS_PYPY, environment_as, make_env, run_pex_command, scie
+from testing import IS_PYPY, make_env, run_pex_command, scie
 
 if TYPE_CHECKING:
     from typing import Any, Iterable, Iterator, List, Tuple
diff --git a/tests/resolve/test_target_options.py b/tests/resolve/test_target_options.py
index 832cbb7ae..2a75bacbf 100644
--- a/tests/resolve/test_target_options.py
+++ b/tests/resolve/test_target_options.py
@@ -10,6 +10,7 @@
 import pytest
 
 import pex.resolve.target_configuration
+from pex.common import environment_as
 from pex.interpreter import PythonInterpreter
 from pex.pep_425 import CompatibilityTags
 from pex.pep_508 import MarkerEnvironment
@@ -20,7 +21,7 @@
 from pex.targets import CompletePlatform, Targets
 from pex.typing import TYPE_CHECKING
 from pex.variables import ENV
-from testing import IS_MAC, environment_as
+from testing import IS_MAC
 
 if TYPE_CHECKING:
     from typing import Any, Dict, Iterable, List, Optional, Tuple, Type
diff --git a/tests/test_atomic_directory.py b/tests/test_atomic_directory.py
index 771b37ceb..c2060b264 100644
--- a/tests/test_atomic_directory.py
+++ b/tests/test_atomic_directory.py
@@ -9,9 +9,8 @@
 import pytest
 
 from pex.atomic_directory import AtomicDirectory, FileLockStyle, _is_bsd_lock, atomic_directory
-from pex.common import temporary_dir, touch
+from pex.common import environment_as, temporary_dir, touch
 from pex.typing import TYPE_CHECKING
-from testing import environment_as
 
 try:
     from unittest import mock
diff --git a/tests/test_interpreter.py b/tests/test_interpreter.py
index 8a8a80bda..de95e0661 100644
--- a/tests/test_interpreter.py
+++ b/tests/test_interpreter.py
@@ -14,7 +14,7 @@
 import pytest
 
 from pex.cache.dirs import InterpreterDir
-from pex.common import chmod_plus_x, safe_mkdir, safe_mkdtemp, temporary_dir, touch
+from pex.common import chmod_plus_x, environment_as, safe_mkdir, safe_mkdtemp, temporary_dir, touch
 from pex.executor import Executor
 from pex.interpreter import PythonInterpreter, create_shebang
 from pex.jobs import Job
@@ -30,7 +30,6 @@
     ensure_python_distribution,
     ensure_python_interpreter,
     ensure_python_venv,
-    environment_as,
     pushd,
 )
 from testing.pytest.tmp import TempdirFactory
diff --git a/tests/test_pex.py b/tests/test_pex.py
index 81a2d0b0c..3a0a55ac6 100644
--- a/tests/test_pex.py
+++ b/tests/test_pex.py
@@ -16,7 +16,7 @@
 import pytest
 
 from pex import resolver
-from pex.common import safe_mkdir, safe_open, temporary_dir
+from pex.common import environment_as, safe_mkdir, safe_open, temporary_dir
 from pex.compatibility import PY2, WINDOWS, to_bytes
 from pex.dist_metadata import Distribution
 from pex.interpreter import PythonIdentity, PythonInterpreter
@@ -33,7 +33,6 @@
     PY_VER,
     WheelBuilder,
     ensure_python_interpreter,
-    environment_as,
     install_wheel,
     make_bdist,
     run_simple_pex,
diff --git a/tests/test_pip.py b/tests/test_pip.py
index ca66c9a3f..172ab2378 100644
--- a/tests/test_pip.py
+++ b/tests/test_pip.py
@@ -13,7 +13,7 @@
 
 import pytest
 
-from pex.common import safe_rmtree
+from pex.common import environment_as, safe_rmtree
 from pex.dist_metadata import Distribution, Requirement
 from pex.interpreter import PythonInterpreter
 from pex.jobs import Job
@@ -29,7 +29,7 @@
 from pex.typing import TYPE_CHECKING
 from pex.variables import ENV
 from pex.venv.virtualenv import Virtualenv
-from testing import IS_LINUX, PY310, ensure_python_interpreter, environment_as
+from testing import IS_LINUX, PY310, ensure_python_interpreter
 from testing.pytest.tmp import Tempdir
 
 if TYPE_CHECKING:
diff --git a/tests/test_requirements.py b/tests/test_requirements.py
index db9bb3348..7a53f0c6c 100644
--- a/tests/test_requirements.py
+++ b/tests/test_requirements.py
@@ -8,7 +8,7 @@
 
 import pytest
 
-from pex.common import safe_open, temporary_dir, touch
+from pex.common import environment_as, safe_open, temporary_dir, touch
 from pex.dist_metadata import Requirement
 from pex.fetcher import URLFetcher
 from pex.requirements import (
@@ -30,7 +30,6 @@
 )
 from pex.third_party.packaging.markers import Marker
 from pex.typing import TYPE_CHECKING
-from testing import environment_as
 
 if TYPE_CHECKING:
     from typing import Any, Iterable, Iterator, List, Optional, Union
diff --git a/tests/test_variables.py b/tests/test_variables.py
index 88e9c2277..25b85e21a 100644
--- a/tests/test_variables.py
+++ b/tests/test_variables.py
@@ -7,12 +7,12 @@
 import pytest
 
 from pex import pex_warnings
+from pex.common import environment_as
 from pex.compatibility import PY2
 from pex.pex_warnings import PEXWarning
 from pex.typing import TYPE_CHECKING
 from pex.util import named_temporary_file
 from pex.variables import NoValueError, Variables
-from testing import environment_as
 from testing.pytest.tmp import Tempdir
 
 if TYPE_CHECKING: