Adapt gsutil unit tests for system dependencies and pytest.
Update imports and compatibility helpers to work with the system boto
package instead of its bundled version. Prevent gsutil's command-line
argument parser from processing pytest arguments during test collection.
Add pytest initialization for gsutil's signal handling, UI controller,
and multiprocessing infrastructure. Disable integration tests and run
tests marked with RequiresIsolation in separate subprocesses, matching
the isolation behavior of gsutil's native test runner.
--- ../gslib/tests/util.py	2026-10-18 13:12:14.804958420 +0300
+++ ../gslib/tests/util.py	2026-10-18 13:12:58.569798518 +0300
@@ -43,7 +43,7 @@
 import gslib
 from gslib.kms_api import KmsApi
 from gslib.project_id import PopulateProjectId
-import mock_storage_service  # From boto/tests/integration/s3
+from gslib.tests import mock_storage_service
 
 from gslib.cloud_api import ResumableDownloadException
 from gslib.cloud_api import ResumableUploadException
--- ../gslib/vendored/boto/tests/integration/s3/mock_storage_service.py	2026-10-18 13:44:29.167214812 +0300
+++ ../gslib/vendored/boto/tests/integration/s3/mock_storage_service.py	2026-10-18 13:45:06.007420005 +0300
@@ -29,6 +29,7 @@
 import copy
 import boto
 import base64
+import io
 import re
 import six
 from hashlib import md5
@@ -36,9 +37,24 @@
 from boto.utils import compute_md5
 from boto.utils import find_matching_headers
 from boto.utils import merge_headers_by_name
-from boto.utils import write_to_fd
 from boto.s3.prefix import Prefix
-from boto.compat import six
+
+
+def write_to_fd(fd, data):
+    """Write given data to given file descriptor, doing any conversions needed."""
+    if isinstance(data, bytes):
+        if ((hasattr(fd, 'mode') and 'b' in fd.mode) or
+                isinstance(fd, io.BytesIO)):
+            fd.write(data)
+        elif hasattr(fd, 'buffer'):
+            fd.buffer.write(data)
+        else:
+            fd.write(six.ensure_text(data))
+    elif hasattr(fd, 'mode') and 'b' in fd.mode:
+        fd.write(six.ensure_binary(data))
+    else:
+        fd.write(data)
+
 
 NOT_IMPL = None
 
--- ../gslib/tests/testcase/unit_testcase.py	2026-10-18 13:55:28.211802315 +0300
+++ ../gslib/tests/testcase/unit_testcase.py	2026-10-18 13:56:23.086982608 +0300
@@ -27,7 +27,6 @@
 import six
 
 import boto
-from boto.utils import get_utf8able_str
 from gslib import project_id
 from gslib import wildcard_iterator
 from gslib.boto_translation import BotoTranslation
@@ -157,8 +156,8 @@
         stderr = sys.stderr.buffer.read()
     [six.ensure_text(string) for string in self.accumulated_stderr]
     [six.ensure_text(string) for string in self.accumulated_stdout]
-    stdout = six.ensure_text(get_utf8able_str(stdout))
-    stderr = six.ensure_text(get_utf8able_str(stderr))
+    stdout = six.ensure_text(stdout)
+    stderr = six.ensure_text(stderr)
     stdout += ''.join(self.accumulated_stdout)
     stderr += ''.join(self.accumulated_stderr)
     _AttemptToCloseSysFd(sys.stdout)
--- ../gslib/tests/test_gsutil.py	2026-10-18 14:23:48.121076040 +0300
+++ ../gslib/tests/test_gsutil.py	2026-10-18 14:24:40.116182691 +0300
@@ -33,6 +33,11 @@
 import gslib
 import gslib.tests.testcase as testcase
 
+# gslib.__main__ parses command-line arguments during import.
+# Prevent it from interpreting pytest's arguments as gsutil options.
+with mock.patch.object(sys, 'argv', ['gsutil']):
+  import gslib.__main__
+
 try:
   from gsutil import _fix_google_module  # pylint: disable=g-import-not-at-top
   FIX_GOOGLE_MODULE_FUNCTION_AVAILABLE = True
--- /dev/null	2026-10-11 18:59:36.659620561 +0300
+++ ../gslib/tests/conftest.py	2026-10-18 16:28:00.041944316 +0300
@@ -0,0 +1,63 @@
+import os
+import subprocess
+import sys
+import pytest
+
+from gslib.tests import util
+from gslib import command
+from gslib import boto_translation
+from gslib.sig_handling import InitializeSignalHandling
+from gslib.utils.parallelism_framework_util import (
+    CheckMultiprocessingAvailableAndInit,
+)
+from gslib.ui_controller import UIController
+
+util.RUN_INTEGRATION_TESTS = False
+
+def pytest_sessionstart(session):
+    InitializeSignalHandling()
+    command.ui_controller = UIController()
+
+    if CheckMultiprocessingAvailableAndInit().is_available:
+        command.InitializeMultiprocessingVariables()
+        boto_translation.InitializeMultiprocessingVariables()
+    else:
+        command.InitializeThreadingVariables()
+
+def pytest_collection_modifyitems(items):
+    if os.environ.get("GSUTIL_PYTEST_ISOLATED") == "1":
+        return
+
+    for item in items:
+        if not getattr(getattr(item, "obj", None),
+                       "requires_isolation", False):
+            continue
+
+        nodeid = item.nodeid
+
+        def run_isolated(nodeid=nodeid):
+            env = os.environ.copy()
+            env["GSUTIL_PYTEST_ISOLATED"] = "1"
+
+            result = subprocess.run(
+                [
+                    sys.executable,
+                    "-m", "pytest",
+                    "-q",
+                    "-o", "log_cli=true",
+                    "-o", "log_cli_level=INFO",
+                    nodeid,
+                ],
+                env=env,
+                capture_output=True,
+                text=True,
+                check=False,
+            )
+
+            if result.returncode:
+                pytest.fail(
+                    f"Isolated test failed:\n{result.stdout}\n{result.stderr}",
+                    pytrace=False,
+                )
+
+        item.obj = run_isolated