diff --git a/tests/test_oauth2client.py b/tests/test_oauth2client.py
index de11810..14beb97 100644
--- a/tests/test_oauth2client.py
+++ b/tests/test_oauth2client.py
@@ -22,6 +22,7 @@
 
 __author__ = 'jcgregorio@google.com (Joe Gregorio)'
 
+import datetime
 import httplib2
 import unittest
 import urlparse
@@ -31,6 +32,16 @@
 except ImportError:
     from cgi import parse_qs
 
+try:  # pragma: no cover
+  import simplejson
+except ImportError:  # pragma: no cover
+  try:
+    # Try to import from django, should work on App Engine
+    from django.utils import simplejson
+  except ImportError:
+    # Should work for Python2.6 and higher.
+    import json as simplejson
+
 from apiclient.http import HttpMockSequence
 from oauth2client.client import AccessTokenCredentials
 from oauth2client.client import AccessTokenCredentialsError
@@ -48,7 +59,7 @@
     client_id = "some_client_id"
     client_secret = "cOuDdkfjxxnv+"
     refresh_token = "1/0/a.df219fjls0"
-    token_expiry = "ignored"
+    token_expiry = datetime.datetime.utcnow()
     token_uri = "https://www.google.com/accounts/o8/oauth2/token"
     user_agent = "refresh_checker/1.0"
     self.credentials = OAuth2Credentials(
@@ -86,6 +97,12 @@
     resp, content = http.request("http://example.com")
     self.assertEqual(400, resp.status)
 
+  def test_to_from_json(self):
+    json = self.credentials.to_json()
+    instance = OAuth2Credentials.from_json(json)
+    self.assertEquals(type(instance), OAuth2Credentials)
+    self.assertEquals(self.credentials.__dict__, instance.__dict__)
+
 
 class AccessTokenCredentialsTests(unittest.TestCase):
 
diff --git a/tests/test_oauth2client_appengine.py b/tests/test_oauth2client_appengine.py
index f9b5094..9362220 100644
--- a/tests/test_oauth2client_appengine.py
+++ b/tests/test_oauth2client_appengine.py
@@ -173,7 +173,7 @@
     self.assertEqual('code', q['response_type'][0])
     self.assertEqual(False, self.decorator.has_credentials())
 
-    # Now simulate the callback to /oauth2callback
+    # Now simulate the callback to /oauth2callback.
     response = self.app.get('/oauth2callback', {
         'code': 'foo_access_code',
         'state': 'foo_path',
@@ -181,7 +181,7 @@
     self.assertEqual('http://localhost/foo_path', response.headers['Location'])
     self.assertEqual(None, self.decorator.credentials)
 
-    # Now requesting the decorated path should work
+    # Now requesting the decorated path should work.
     response = self.app.get('/foo_path')
     self.assertEqual('200 OK', response.status)
     self.assertEqual(True, self.decorator.has_credentials())
@@ -190,18 +190,18 @@
     self.assertEqual('foo_access_token',
                      self.decorator.credentials.access_token)
 
-    # Invalidate the stored Credentials
+    # Invalidate the stored Credentials.
     self.decorator.credentials.invalid = True
     self.decorator.credentials.store.put(self.decorator.credentials)
 
-    # Invalid Credentials should start the OAuth dance again
+    # Invalid Credentials should start the OAuth dance again.
     response = self.app.get('/foo_path')
     self.assertTrue(response.status.startswith('302'))
     q = parse_qs(response.headers['Location'].split('?', 1)[1])
     self.assertEqual('http://localhost/oauth2callback', q['redirect_uri'][0])
 
   def test_aware(self):
-    # An initial request to an oauth_aware decorated path should not redirect
+    # An initial request to an oauth_aware decorated path should not redirect.
     response = self.app.get('/bar_path')
     self.assertEqual('Hello World!', response.body)
     self.assertEqual('200 OK', response.status)
@@ -214,7 +214,7 @@
     self.assertEqual('http://localhost/bar_path', q['state'][0])
     self.assertEqual('code', q['response_type'][0])
 
-    # Now simulate the callback to /oauth2callback
+    # Now simulate the callback to /oauth2callback.
     url = self.decorator.authorize_url()
     response = self.app.get('/oauth2callback', {
         'code': 'foo_access_code',
@@ -223,7 +223,7 @@
     self.assertEqual('http://localhost/bar_path', response.headers['Location'])
     self.assertEqual(False, self.decorator.has_credentials())
 
-    # Now requesting the decorated path will have credentials
+    # Now requesting the decorated path will have credentials.
     response = self.app.get('/bar_path')
     self.assertEqual('200 OK', response.status)
     self.assertEqual('Hello World!', response.body)
diff --git a/tests/test_oauth2client_file.py b/tests/test_oauth2client_file.py
new file mode 100644
index 0000000..05deaa0
--- /dev/null
+++ b/tests/test_oauth2client_file.py
@@ -0,0 +1,157 @@
+#!/usr/bin/python2.4
+#
+# Copyright 2010 Google Inc.
+#
+# 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.
+
+
+"""Oauth2client.file tests
+
+Unit tests for oauth2client.file
+"""
+
+__author__ = 'jcgregorio@google.com (Joe Gregorio)'
+
+import os
+import pickle
+import unittest
+import datetime
+
+
+try:  # pragma: no cover
+  import simplejson
+except ImportError:  # pragma: no cover
+  try:
+    # Try to import from django, should work on App Engine
+    from django.utils import simplejson
+  except ImportError:
+    # Should work for Python2.6 and higher.
+    import json as simplejson
+
+
+from oauth2client.client import OAuth2Credentials
+from oauth2client.client import AccessTokenCredentials
+from oauth2client.client import AssertionCredentials
+from oauth2client.file import Storage
+from oauth2client import multistore_file
+
+
+FILENAME = os.path.join(os.path.dirname(__file__), 'test_file_storage.data')
+
+
+class OAuth2ClientFileTests(unittest.TestCase):
+
+  def tearDown(self):
+    try:
+      os.unlink(FILENAME)
+    except OSError:
+      pass
+
+  def setUp(self):
+    try:
+      os.unlink(FILENAME)
+    except OSError:
+      pass
+
+  def test_non_existent_file_storage(self):
+    s = Storage(FILENAME)
+    credentials = s.get()
+    self.assertEquals(None, credentials)
+
+  def test_pickle_and_json_interop(self):
+    # Write a file with a pickled OAuth2Credentials.
+    access_token = 'foo'
+    client_id = 'some_client_id'
+    client_secret = 'cOuDdkfjxxnv+'
+    refresh_token = '1/0/a.df219fjls0'
+    token_expiry = datetime.datetime.utcnow()
+    token_uri = 'https://www.google.com/accounts/o8/oauth2/token'
+    user_agent = 'refresh_checker/1.0'
+
+    credentials = OAuth2Credentials(
+        access_token, client_id, client_secret,
+        refresh_token, token_expiry, token_uri,
+        user_agent)
+
+    f = open(FILENAME, 'w')
+    pickle.dump(credentials, f)
+    f.close()
+
+    # Storage should be able to read that object.
+    # TODO(jcgregorio) This should fail once pickle support is removed.
+    s = Storage(FILENAME)
+    credentials = s.get()
+    self.assertNotEquals(None, credentials)
+    self.assertEquals('foo', credentials.access_token)
+
+    # Now write it back out and confirm it has been rewritten as JSON
+    s.put(credentials)
+    f = file(FILENAME)
+    data = simplejson.load(f)
+    f.close()
+
+    self.assertEquals(data['access_token'], 'foo')
+    self.assertEquals(data['_class'], 'OAuth2Credentials')
+    self.assertEquals(data['_module'], 'oauth2client.client')
+
+  def test_access_token_credentials(self):
+    access_token = 'foo'
+    user_agent = 'refresh_checker/1.0'
+
+    credentials = AccessTokenCredentials(access_token, user_agent)
+
+    s = Storage(FILENAME)
+    credentials = s.put(credentials)
+    credentials = s.get()
+
+    self.assertNotEquals(None, credentials)
+    self.assertEquals('foo', credentials.access_token)
+
+  def test_multistore_non_existent_file(self):
+    store = multistore_file.get_credential_storage(
+        FILENAME,
+        'some_client_id',
+        'user-agent/1.0',
+        'some-scope')
+
+    credentials = store.get()
+    self.assertEquals(None, credentials)
+
+  def test_multistore_file(self):
+    access_token = 'foo'
+    client_secret = 'cOuDdkfjxxnv+'
+    refresh_token = '1/0/a.df219fjls0'
+    token_expiry = datetime.datetime.utcnow()
+    token_uri = 'https://www.google.com/accounts/o8/oauth2/token'
+    user_agent = 'refresh_checker/1.0'
+    client_id = 'some_client_id'
+
+    credentials = OAuth2Credentials(
+        access_token, client_id, client_secret,
+        refresh_token, token_expiry, token_uri,
+        user_agent)
+
+    store = multistore_file.get_credential_storage(
+        FILENAME,
+        credentials.client_id,
+        credentials.user_agent,
+        'some-scope')
+
+    store.put(credentials)
+    credentials = store.get()
+
+    self.assertNotEquals(None, credentials)
+    self.assertEquals('foo', credentials.access_token)
+
+if __name__ == '__main__':
+  unittest.main()