diff --git a/tools/releasetools/test_common.py b/tools/releasetools/test_common.py
new file mode 100644
index 0000000..f163f92
--- /dev/null
+++ b/tools/releasetools/test_common.py
@@ -0,0 +1,108 @@
+#
+# Copyright (C) 2015 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+import os
+import tempfile
+import time
+import unittest
+import zipfile
+
+import common
+
+
+def random_string_with_holes(size, block_size, step_size):
+  data = ["\0"] * size
+  for begin in range(0, size, step_size):
+    end = begin + block_size
+    data[begin:end] = os.urandom(block_size)
+  return "".join(data)
+
+
+class CommonZipTest(unittest.TestCase):
+  def _test_ZipWrite(self, contents, extra_zipwrite_args=None):
+    extra_zipwrite_args = dict(extra_zipwrite_args or {})
+
+    test_file = tempfile.NamedTemporaryFile(delete=False)
+    zip_file = tempfile.NamedTemporaryFile(delete=False)
+
+    test_file_name = test_file.name
+    zip_file_name = zip_file.name
+
+    # File names within an archive strip the leading slash.
+    arcname = extra_zipwrite_args.get("arcname", test_file_name)
+    if arcname[0] == "/":
+      arcname = arcname[1:]
+
+    zip_file.close()
+    zip_file = zipfile.ZipFile(zip_file_name, "w")
+
+    try:
+      test_file.write(contents)
+      test_file.close()
+
+      old_stat = os.stat(test_file_name)
+      expected_mode = extra_zipwrite_args.get("perms", 0o644)
+
+      time.sleep(5)  # Make sure the atime/mtime will change measurably.
+
+      common.ZipWrite(zip_file, test_file_name, **extra_zipwrite_args)
+
+      new_stat = os.stat(test_file_name)
+      self.assertEqual(int(old_stat.st_mode), int(new_stat.st_mode))
+      self.assertEqual(int(old_stat.st_mtime), int(new_stat.st_mtime))
+
+      zip_file.close()
+      zip_file = zipfile.ZipFile(zip_file_name, "r")
+      info = zip_file.getinfo(arcname)
+
+      self.assertEqual(info.date_time, (2009, 1, 1, 0, 0, 0))
+      mode = (info.external_attr >> 16) & 0o777
+      self.assertEqual(mode, expected_mode)
+      self.assertEqual(zip_file.read(arcname), contents)
+    finally:
+      os.remove(test_file_name)
+      os.remove(zip_file_name)
+
+  def test_ZipWrite(self):
+    file_contents = os.urandom(1024)
+    self._test_ZipWrite(file_contents)
+
+  def test_ZipWrite_with_opts(self):
+    file_contents = os.urandom(1024)
+    self._test_ZipWrite(file_contents, {
+        "arcname": "foobar",
+        "perms": 0o777,
+        "compress_type": zipfile.ZIP_DEFLATED,
+    })
+
+  def test_ZipWrite_large_file(self):
+    kilobytes = 1024
+    megabytes = 1024 * kilobytes
+    gigabytes = 1024 * megabytes
+
+    size = int(2 * gigabytes + 1)
+    block_size = 4 * kilobytes
+    step_size = 4 * megabytes
+    file_contents = random_string_with_holes(
+        size, block_size, step_size)
+    self._test_ZipWrite(file_contents, {
+        "compress_type": zipfile.ZIP_DEFLATED,
+    })
+
+  def test_ZipWrite_resets_ZIP64_LIMIT(self):
+    default_limit = (1 << 31) - 1
+    self.assertEqual(default_limit, zipfile.ZIP64_LIMIT)
+    self._test_ZipWrite('')
+    self.assertEqual(default_limit, zipfile.ZIP64_LIMIT)