3 files changed, 19 insertions, 0 deletions
diff --git a/tests/test_find_top_level.py b/tests/test_find_top_level.py
index 184fe72..c4df873 100644
--- a/tests/test_find_top_level.py
+++ b/tests/test_find_top_level.py
@@ -11,6 +11,8 @@ import pytest
 
 from gemato.find_top_level import find_top_level_manifest
 
+from tests.testutil import disallow_writes
+
 
 @pytest.fixture(scope='module')
 def plain_tree(tmp_path_factory):
@@ -33,6 +35,7 @@ IGNORE ignored-empty-dir
               'ignored-dir/Manifest'):
         with open(tmp_path / f, 'w'):
             pass
+    disallow_writes(tmp_path)
     yield tmp_path
 
 
@@ -107,6 +110,7 @@ IGNORE ignored-empty-dir
               'ignored-dir/Manifest.gz'):
         with gzip.GzipFile(tmp_path / f, 'w'):
             pass
+    disallow_writes(tmp_path)
     yield tmp_path
 
 
diff --git a/tests/test_verify.py b/tests/test_verify.py
index 79c5513..1f3170b 100644
--- a/tests/test_verify.py
+++ b/tests/test_verify.py
@@ -24,6 +24,8 @@ from gemato.verify import (
     verify_entry_compatibility,
     )
 
+from tests.testutil import disallow_writes
+
 
 TEST_STRING = b'The quick brown fox jumps over the lazy dog'
 
@@ -46,6 +48,7 @@ def test_tree(tmp_path_factory):
     unix_sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
     unix_sock.bind(str(tmp_path / 'unix-socket'))
     unix_sock.listen(1)
+    disallow_writes(tmp_path)
     yield tmp_path
     unix_sock.close()
 
diff --git a/tests/testutil.py b/tests/testutil.py
index 092a4d2..bde84f7 100644
--- a/tests/testutil.py
+++ b/tests/testutil.py
@@ -11,6 +11,7 @@ import os
 import os.path
 import random
 import shutil
+import stat
 import tempfile
 import threading
 import unittest
@@ -21,6 +22,17 @@ from http.server import HTTPServer, BaseHTTPRequestHandler
 from urllib.parse import urlparse, parse_qs
 
 
+def disallow_writes(path):
+    """Mark path non-writable, recursively"""
+    for dirpath, dirs, files in os.walk(path, topdown=False):
+        for f in files + dirs:
+            st = os.lstat(os.path.join(dirpath, f))
+            if not stat.S_ISLNK(st.st_mode):
+                os.chmod(os.path.join(dirpath, f),
+                         st.st_mode & ~0o222)
+    os.chmod(path, 0o555)
+
+
 class LoggingTestCase(unittest.TestCase):
     def setUp(self):
         self.log = io.StringIO()