diff --git a/maint/appengine/README b/maint/appengine/README
new file mode 100644
index 00000000..6a77f3d2
--- /dev/null
+++ b/maint/appengine/README
@@ -0,0 +1,11 @@
+Unit test support for app engine.  Currently very limited as most of
+our tests depend on direct network access, but these tests ensure that the
+modules that are supposed to work on app engine don't depend on any
+forbidden modules.
+
+The code lives in maint/appengine/common, but should be run from the py25
+or py27 subdirectories (which contain an app.yaml and a bunch of symlinks).
+runtests.py is the entry point; cgi_runtests.py is used internally.
+dev_appserver.py doesn't work with virtualenv
+(http://code.google.com/p/googleappengine/issues/detail?id=4339) so these
+tests are not hooked into tox yet.
diff --git a/maint/appengine/common/cgi_runtests.py b/maint/appengine/common/cgi_runtests.py
new file mode 100644
index 00000000..13f0d91d
--- /dev/null
+++ b/maint/appengine/common/cgi_runtests.py
@@ -0,0 +1,72 @@
+#!/usr/bin/env python
+import logging
+import unittest
+
+# Most of our tests depend on IOLoop, which is not importable on app engine.
+# Run the tests that work, and check that forbidden imports don't sneak
+# in to modules that are supposed to work on app engine.
+TEST_MODULES = [
+    'tornado.httputil.doctests',
+    #'tornado.iostream.doctests',
+    'tornado.util.doctests',
+    #'tornado.test.auth_test',
+    #'tornado.test.curl_httpclient_test',
+    'tornado.test.escape_test',
+    #'tornado.test.gen_test',
+    #'tornado.test.httpclient_test',
+    #'tornado.test.httpserver_test',
+    'tornado.test.httputil_test',
+    #'tornado.test.import_test',
+    #'tornado.test.ioloop_test',
+    #'tornado.test.iostream_test',
+    #'tornado.test.process_test',
+    #'tornado.test.simple_httpclient_test',
+    #'tornado.test.stack_context_test',
+    'tornado.test.template_test',
+    #'tornado.test.testing_test',
+    #'tornado.test.twisted_test',
+    #'tornado.test.web_test',
+    #'tornado.test.wsgi_test',
+]
+
+def import_everything():
+    # import tornado.auth
+    # import tornado.autoreload
+    # import tornado.curl_httpclient  # depends on pycurl
+    # import tornado.database  # depends on MySQLdb
+    import tornado.escape
+    # import tornado.httpclient
+    # import tornado.httpserver
+    import tornado.httputil
+    # import tornado.ioloop
+    # import tornado.iostream
+    import tornado.locale
+    import tornado.options
+    # import tornado.netutil
+    # import tornado.platform.twisted # depends on twisted
+    # import tornado.process
+    # import tornado.simple_httpclient
+    import tornado.stack_context
+    import tornado.template
+    import tornado.testing
+    import tornado.util
+    import tornado.web
+    # import tornado.websocket
+    import tornado.wsgi
+    
+def all():
+    return unittest.defaultTestLoader.loadTestsFromNames(TEST_MODULES)
+
+if __name__ == '__main__':
+    print "Content-Type: text/plain\r\n\r\n",
+
+    import_everything()
+
+    import tornado.testing
+    try:
+        tornado.testing.main()
+    except SystemExit, e:
+        if e.code == 0:
+            print "PASS"
+        else:
+            raise
diff --git a/maint/appengine/common/runtests.py b/maint/appengine/common/runtests.py
new file mode 100644
index 00000000..c648285f
--- /dev/null
+++ b/maint/appengine/common/runtests.py
@@ -0,0 +1,29 @@
+#!/usr/bin/env python
+
+import os
+import random
+import signal
+import subprocess
+import sys
+import time
+import urllib2
+
+if __name__ == "__main__":
+    tornado_root = os.path.abspath(os.path.join(os.path.dirname(__file__),
+                                                '../../..'))
+    # dev_appserver doesn't seem to set SO_REUSEADDR
+    port = random.randrange(10000, 11000)
+    # does dev_appserver.py ever live anywhere but /usr/local/bin?
+    proc = subprocess.Popen([sys.executable,
+                             "/usr/local/bin/dev_appserver.py",
+                             os.path.dirname(__file__),
+                             "--port=%d" % port
+                             ],
+                            cwd=tornado_root)
+    time.sleep(3)
+    try:
+        resp = urllib2.urlopen("http://localhost:%d/" % port)
+        print resp.read()
+    finally:
+        os.kill(proc.pid, signal.SIGTERM)
+        proc.wait()
diff --git a/maint/appengine/py25/app.yaml b/maint/appengine/py25/app.yaml
new file mode 100644
index 00000000..8bd78921
--- /dev/null
+++ b/maint/appengine/py25/app.yaml
@@ -0,0 +1,8 @@
+application: tornado-tests-appengine25
+version: 1
+runtime: python
+api_version: 1
+
+handlers:
+- url: /
+  script: cgi_runtests.py
\ No newline at end of file
diff --git a/maint/appengine/py25/cgi_runtests.py b/maint/appengine/py25/cgi_runtests.py
new file mode 120000
index 00000000..a9fc90e9
--- /dev/null
+++ b/maint/appengine/py25/cgi_runtests.py
@@ -0,0 +1 @@
+../common/cgi_runtests.py
\ No newline at end of file
diff --git a/maint/appengine/py25/runtests.py b/maint/appengine/py25/runtests.py
new file mode 120000
index 00000000..2cce26b0
--- /dev/null
+++ b/maint/appengine/py25/runtests.py
@@ -0,0 +1 @@
+../common/runtests.py
\ No newline at end of file
diff --git a/maint/appengine/py25/tornado b/maint/appengine/py25/tornado
new file mode 120000
index 00000000..13b2e093
--- /dev/null
+++ b/maint/appengine/py25/tornado
@@ -0,0 +1 @@
+../../../tornado
\ No newline at end of file
diff --git a/maint/appengine/py27/app.yaml b/maint/appengine/py27/app.yaml
new file mode 100644
index 00000000..e5dea072
--- /dev/null
+++ b/maint/appengine/py27/app.yaml
@@ -0,0 +1,9 @@
+application: tornado-tests-appengine27
+version: 1
+runtime: python27
+threadsafe: false
+api_version: 1
+
+handlers:
+- url: /
+  script: cgi_runtests.py
\ No newline at end of file
diff --git a/maint/appengine/py27/cgi_runtests.py b/maint/appengine/py27/cgi_runtests.py
new file mode 120000
index 00000000..a9fc90e9
--- /dev/null
+++ b/maint/appengine/py27/cgi_runtests.py
@@ -0,0 +1 @@
+../common/cgi_runtests.py
\ No newline at end of file
diff --git a/maint/appengine/py27/runtests.py b/maint/appengine/py27/runtests.py
new file mode 120000
index 00000000..2cce26b0
--- /dev/null
+++ b/maint/appengine/py27/runtests.py
@@ -0,0 +1 @@
+../common/runtests.py
\ No newline at end of file
diff --git a/maint/appengine/py27/tornado b/maint/appengine/py27/tornado
new file mode 120000
index 00000000..13b2e093
--- /dev/null
+++ b/maint/appengine/py27/tornado
@@ -0,0 +1 @@
+../../../tornado
\ No newline at end of file
diff --git a/tornado/testing.py b/tornado/testing.py
index bf49edf8..a03d15d7 100644
--- a/tornado/testing.py
+++ b/tornado/testing.py
@@ -21,8 +21,16 @@ information.
 from __future__ import with_statement
 
 from cStringIO import StringIO
-from tornado.httpclient import AsyncHTTPClient
-from tornado.httpserver import HTTPServer
+try:
+    from tornado.httpclient import AsyncHTTPClient
+    from tornado.httpserver import HTTPServer
+    from tornado.ioloop import IOLoop
+except ImportError:
+    # These modules are not importable on app engine.  Parts of this module
+    # won't work, but e.g. LogTrapTestCase and main() will.
+    AsyncHTTPClient = None
+    HTTPServer = None
+    IOLoop = None
 from tornado.stack_context import StackContext, NullContext
 import contextlib
 import logging
@@ -31,8 +39,6 @@ import sys
 import time
 import unittest
 
-from tornado.ioloop import IOLoop
-
 _next_port = 10000
 def get_unused_port():
     """Returns a (hopefully) unused port number."""