diff --git a/Lib/test/test_wsgiref.py b/Lib/test/test_wsgiref.py
new file mode 100644
index 000000000..6af45145a
--- /dev/null
+++ b/Lib/test/test_wsgiref.py
@@ -0,0 +1,866 @@
+from unittest import mock
+from test import support
+from test.test_httpservers import NoLogRequestHandler
+from unittest import TestCase
+from wsgiref.util import setup_testing_defaults
+from wsgiref.headers import Headers
+from wsgiref.handlers import BaseHandler, BaseCGIHandler, SimpleHandler
+from wsgiref import util
+from wsgiref.validate import validator
+from wsgiref.simple_server import WSGIServer, WSGIRequestHandler
+from wsgiref.simple_server import make_server
+from http.client import HTTPConnection
+from io import StringIO, BytesIO, BufferedReader
+from socketserver import BaseServer
+from platform import python_implementation
+
+import os
+import re
+import signal
+import sys
+import threading
+import unittest
+
+
+class MockServer(WSGIServer):
+    """Non-socket HTTP server"""
+
+    def __init__(self, server_address, RequestHandlerClass):
+        BaseServer.__init__(self, server_address, RequestHandlerClass)
+        self.server_bind()
+
+    def server_bind(self):
+        host, port = self.server_address
+        self.server_name = host
+        self.server_port = port
+        self.setup_environ()
+
+
+class MockHandler(WSGIRequestHandler):
+    """Non-socket HTTP handler"""
+    def setup(self):
+        self.connection = self.request
+        self.rfile, self.wfile = self.connection
+
+    def finish(self):
+        pass
+
+
+def hello_app(environ,start_response):
+    start_response("200 OK", [
+        ('Content-Type','text/plain'),
+        ('Date','Mon, 05 Jun 2006 18:49:54 GMT')
+    ])
+    return [b"Hello, world!"]
+
+
+def header_app(environ, start_response):
+    start_response("200 OK", [
+        ('Content-Type', 'text/plain'),
+        ('Date', 'Mon, 05 Jun 2006 18:49:54 GMT')
+    ])
+    return [';'.join([
+        environ['HTTP_X_TEST_HEADER'], environ['QUERY_STRING'],
+        environ['PATH_INFO']
+    ]).encode('iso-8859-1')]
+
+
+def run_amock(app=hello_app, data=b"GET / HTTP/1.0\n\n"):
+    server = make_server("", 80, app, MockServer, MockHandler)
+    inp = BufferedReader(BytesIO(data))
+    out = BytesIO()
+    olderr = sys.stderr
+    err = sys.stderr = StringIO()
+
+    try:
+        server.finish_request((inp, out), ("127.0.0.1",8888))
+    finally:
+        sys.stderr = olderr
+
+    return out.getvalue(), err.getvalue()
+
+def compare_generic_iter(make_it,match):
+    """Utility to compare a generic 2.1/2.2+ iterator with an iterable
+
+    If running under Python 2.2+, this tests the iterator using iter()/next(),
+    as well as __getitem__.  'make_it' must be a function returning a fresh
+    iterator to be tested (since this may test the iterator twice)."""
+
+    it = make_it()
+    n = 0
+    for item in match:
+        if not it[n]==item: raise AssertionError
+        n+=1
+    try:
+        it[n]
+    except IndexError:
+        pass
+    else:
+        raise AssertionError("Too many items from __getitem__",it)
+
+    try:
+        iter, StopIteration
+    except NameError:
+        pass
+    else:
+        # Only test iter mode under 2.2+
+        it = make_it()
+        if not iter(it) is it: raise AssertionError
+        for item in match:
+            if not next(it) == item: raise AssertionError
+        try:
+            next(it)
+        except StopIteration:
+            pass
+        else:
+            raise AssertionError("Too many items from .__next__()", it)
+
+
+class IntegrationTests(TestCase):
+
+    def check_hello(self, out, has_length=True):
+        pyver = (python_implementation() + "/" +
+                sys.version.split()[0])
+        self.assertEqual(out,
+            ("HTTP/1.0 200 OK\r\n"
+            "Server: WSGIServer/0.2 " + pyver +"\r\n"
+            "Content-Type: text/plain\r\n"
+            "Date: Mon, 05 Jun 2006 18:49:54 GMT\r\n" +
+            (has_length and  "Content-Length: 13\r\n" or "") +
+            "\r\n"
+            "Hello, world!").encode("iso-8859-1")
+        )
+
+    def test_plain_hello(self):
+        out, err = run_amock()
+        self.check_hello(out)
+
+    def test_environ(self):
+        request = (
+            b"GET /p%61th/?query=test HTTP/1.0\n"
+            b"X-Test-Header: Python test \n"
+            b"X-Test-Header: Python test 2\n"
+            b"Content-Length: 0\n\n"
+        )
+        out, err = run_amock(header_app, request)
+        self.assertEqual(
+            out.splitlines()[-1],
+            b"Python test,Python test 2;query=test;/path/"
+        )
+
+    def test_request_length(self):
+        out, err = run_amock(data=b"GET " + (b"x" * 65537) + b" HTTP/1.0\n\n")
+        self.assertEqual(out.splitlines()[0],
+                         b"HTTP/1.0 414 Request-URI Too Long")
+
+    def test_validated_hello(self):
+        out, err = run_amock(validator(hello_app))
+        # the middleware doesn't support len(), so content-length isn't there
+        self.check_hello(out, has_length=False)
+
+    def test_simple_validation_error(self):
+        def bad_app(environ,start_response):
+            start_response("200 OK", ('Content-Type','text/plain'))
+            return ["Hello, world!"]
+        out, err = run_amock(validator(bad_app))
+        self.assertTrue(out.endswith(
+            b"A server error occurred.  Please contact the administrator."
+        ))
+        self.assertEqual(
+            err.splitlines()[-2],
+            "AssertionError: Headers (('Content-Type', 'text/plain')) must"
+            " be of type list: <class 'tuple'>"
+        )
+
+    def test_status_validation_errors(self):
+        def create_bad_app(status):
+            def bad_app(environ, start_response):
+                start_response(status, [("Content-Type", "text/plain; charset=utf-8")])
+                return [b"Hello, world!"]
+            return bad_app
+
+        tests = [
+            ('200', 'AssertionError: Status must be at least 4 characters'),
+            ('20X OK', 'AssertionError: Status message must begin w/3-digit code'),
+            ('200OK', 'AssertionError: Status message must have a space after code'),
+        ]
+
+        for status, exc_message in tests:
+            with self.subTest(status=status):
+                out, err = run_amock(create_bad_app(status))
+                self.assertTrue(out.endswith(
+                    b"A server error occurred.  Please contact the administrator."
+                ))
+                self.assertEqual(err.splitlines()[-2], exc_message)
+
+    def test_wsgi_input(self):
+        def bad_app(e,s):
+            e["wsgi.input"].read()
+            s("200 OK", [("Content-Type", "text/plain; charset=utf-8")])
+            return [b"data"]
+        out, err = run_amock(validator(bad_app))
+        self.assertTrue(out.endswith(
+            b"A server error occurred.  Please contact the administrator."
+        ))
+        self.assertEqual(
+            err.splitlines()[-2], "AssertionError"
+        )
+
+    def test_bytes_validation(self):
+        def app(e, s):
+            s("200 OK", [
+                ("Content-Type", "text/plain; charset=utf-8"),
+                ("Date", "Wed, 24 Dec 2008 13:29:32 GMT"),
+                ])
+            return [b"data"]
+        out, err = run_amock(validator(app))
+        self.assertTrue(err.endswith('"GET / HTTP/1.0" 200 4\n'))
+        ver = sys.version.split()[0].encode('ascii')
+        py  = python_implementation().encode('ascii')
+        pyver = py + b"/" + ver
+        self.assertEqual(
+                b"HTTP/1.0 200 OK\r\n"
+                b"Server: WSGIServer/0.2 "+ pyver + b"\r\n"
+                b"Content-Type: text/plain; charset=utf-8\r\n"
+                b"Date: Wed, 24 Dec 2008 13:29:32 GMT\r\n"
+                b"\r\n"
+                b"data",
+                out)
+
+    def test_cp1252_url(self):
+        def app(e, s):
+            s("200 OK", [
+                ("Content-Type", "text/plain"),
+                ("Date", "Wed, 24 Dec 2008 13:29:32 GMT"),
+                ])
+            # PEP3333 says environ variables are decoded as latin1.
+            # Encode as latin1 to get original bytes
+            return [e["PATH_INFO"].encode("latin1")]
+
+        out, err = run_amock(
+            validator(app), data=b"GET /\x80%80 HTTP/1.0")
+        self.assertEqual(
+            [
+                b"HTTP/1.0 200 OK",
+                mock.ANY,
+                b"Content-Type: text/plain",
+                b"Date: Wed, 24 Dec 2008 13:29:32 GMT",
+                b"",
+                b"/\x80\x80",
+            ],
+            out.splitlines())
+
+    def test_interrupted_write(self):
+        # BaseHandler._write() and _flush() have to write all data, even if
+        # it takes multiple send() calls.  Test this by interrupting a send()
+        # call with a Unix signal.
+        pthread_kill = support.get_attribute(signal, "pthread_kill")
+
+        def app(environ, start_response):
+            start_response("200 OK", [])
+            return [b'\0' * support.SOCK_MAX_SIZE]
+
+        class WsgiHandler(NoLogRequestHandler, WSGIRequestHandler):
+            pass
+
+        server = make_server(support.HOST, 0, app, handler_class=WsgiHandler)
+        self.addCleanup(server.server_close)
+        interrupted = threading.Event()
+
+        def signal_handler(signum, frame):
+            interrupted.set()
+
+        original = signal.signal(signal.SIGUSR1, signal_handler)
+        self.addCleanup(signal.signal, signal.SIGUSR1, original)
+        received = None
+        main_thread = threading.get_ident()
+
+        def run_client():
+            http = HTTPConnection(*server.server_address)
+            http.request("GET", "/")
+            with http.getresponse() as response:
+                response.read(100)
+                # The main thread should now be blocking in a send() system
+                # call.  But in theory, it could get interrupted by other
+                # signals, and then retried.  So keep sending the signal in a
+                # loop, in case an earlier signal happens to be delivered at
+                # an inconvenient moment.
+                while True:
+                    pthread_kill(main_thread, signal.SIGUSR1)
+                    if interrupted.wait(timeout=float(1)):
+                        break
+                nonlocal received
+                received = len(response.read())
+            http.close()
+
+        background = threading.Thread(target=run_client)
+        background.start()
+        server.handle_request()
+        background.join()
+        self.assertEqual(received, support.SOCK_MAX_SIZE - 100)
+
+
+class UtilityTests(TestCase):
+
+    def checkShift(self,sn_in,pi_in,part,sn_out,pi_out):
+        env = {'SCRIPT_NAME':sn_in,'PATH_INFO':pi_in}
+        util.setup_testing_defaults(env)
+        self.assertEqual(util.shift_path_info(env),part)
+        self.assertEqual(env['PATH_INFO'],pi_out)
+        self.assertEqual(env['SCRIPT_NAME'],sn_out)
+        return env
+
+    def checkDefault(self, key, value, alt=None):
+        # Check defaulting when empty
+        env = {}
+        util.setup_testing_defaults(env)
+        if isinstance(value, StringIO):
+            self.assertIsInstance(env[key], StringIO)
+        elif isinstance(value,BytesIO):
+            self.assertIsInstance(env[key],BytesIO)
+        else:
+            self.assertEqual(env[key], value)
+
+        # Check existing value
+        env = {key:alt}
+        util.setup_testing_defaults(env)
+        self.assertIs(env[key], alt)
+
+    def checkCrossDefault(self,key,value,**kw):
+        util.setup_testing_defaults(kw)
+        self.assertEqual(kw[key],value)
+
+    def checkAppURI(self,uri,**kw):
+        util.setup_testing_defaults(kw)
+        self.assertEqual(util.application_uri(kw),uri)
+
+    def checkReqURI(self,uri,query=1,**kw):
+        util.setup_testing_defaults(kw)
+        self.assertEqual(util.request_uri(kw,query),uri)
+
+    @support.ignore_warnings(category=DeprecationWarning)
+    def checkFW(self,text,size,match):
+
+        def make_it(text=text,size=size):
+            return util.FileWrapper(StringIO(text),size)
+
+        compare_generic_iter(make_it,match)
+
+        it = make_it()
+        self.assertFalse(it.filelike.closed)
+
+        for item in it:
+            pass
+
+        self.assertFalse(it.filelike.closed)
+
+        it.close()
+        self.assertTrue(it.filelike.closed)
+
+    def test_filewrapper_getitem_deprecation(self):
+        wrapper = util.FileWrapper(StringIO('foobar'), 3)
+        with self.assertWarnsRegex(DeprecationWarning,
+                                   r'Use iterator protocol instead'):
+            # This should have returned 'bar'.
+            self.assertEqual(wrapper[1], 'foo')
+
+    def testSimpleShifts(self):
+        self.checkShift('','/', '', '/', '')
+        self.checkShift('','/x', 'x', '/x', '')
+        self.checkShift('/','', None, '/', '')
+        self.checkShift('/a','/x/y', 'x', '/a/x', '/y')
+        self.checkShift('/a','/x/',  'x', '/a/x', '/')
+
+    def testNormalizedShifts(self):
+        self.checkShift('/a/b', '/../y', '..', '/a', '/y')
+        self.checkShift('', '/../y', '..', '', '/y')
+        self.checkShift('/a/b', '//y', 'y', '/a/b/y', '')
+        self.checkShift('/a/b', '//y/', 'y', '/a/b/y', '/')
+        self.checkShift('/a/b', '/./y', 'y', '/a/b/y', '')
+        self.checkShift('/a/b', '/./y/', 'y', '/a/b/y', '/')
+        self.checkShift('/a/b', '///./..//y/.//', '..', '/a', '/y/')
+        self.checkShift('/a/b', '///', '', '/a/b/', '')
+        self.checkShift('/a/b', '/.//', '', '/a/b/', '')
+        self.checkShift('/a/b', '/x//', 'x', '/a/b/x', '/')
+        self.checkShift('/a/b', '/.', None, '/a/b', '')
+
+    def testDefaults(self):
+        for key, value in [
+            ('SERVER_NAME','127.0.0.1'),
+            ('SERVER_PORT', '80'),
+            ('SERVER_PROTOCOL','HTTP/1.0'),
+            ('HTTP_HOST','127.0.0.1'),
+            ('REQUEST_METHOD','GET'),
+            ('SCRIPT_NAME',''),
+            ('PATH_INFO','/'),
+            ('wsgi.version', (1,0)),
+            ('wsgi.run_once', 0),
+            ('wsgi.multithread', 0),
+            ('wsgi.multiprocess', 0),
+            ('wsgi.input', BytesIO()),
+            ('wsgi.errors', StringIO()),
+            ('wsgi.url_scheme','http'),
+        ]:
+            self.checkDefault(key,value)
+
+    def testCrossDefaults(self):
+        self.checkCrossDefault('HTTP_HOST',"foo.bar",SERVER_NAME="foo.bar")
+        self.checkCrossDefault('wsgi.url_scheme',"https",HTTPS="on")
+        self.checkCrossDefault('wsgi.url_scheme',"https",HTTPS="1")
+        self.checkCrossDefault('wsgi.url_scheme',"https",HTTPS="yes")
+        self.checkCrossDefault('wsgi.url_scheme',"http",HTTPS="foo")
+        self.checkCrossDefault('SERVER_PORT',"80",HTTPS="foo")
+        self.checkCrossDefault('SERVER_PORT',"443",HTTPS="on")
+
+    def testGuessScheme(self):
+        self.assertEqual(util.guess_scheme({}), "http")
+        self.assertEqual(util.guess_scheme({'HTTPS':"foo"}), "http")
+        self.assertEqual(util.guess_scheme({'HTTPS':"on"}), "https")
+        self.assertEqual(util.guess_scheme({'HTTPS':"yes"}), "https")
+        self.assertEqual(util.guess_scheme({'HTTPS':"1"}), "https")
+
+    def testAppURIs(self):
+        self.checkAppURI("http://127.0.0.1/")
+        self.checkAppURI("http://127.0.0.1/spam", SCRIPT_NAME="/spam")
+        self.checkAppURI("http://127.0.0.1/sp%E4m", SCRIPT_NAME="/sp\xe4m")
+        self.checkAppURI("http://spam.example.com:2071/",
+            HTTP_HOST="spam.example.com:2071", SERVER_PORT="2071")
+        self.checkAppURI("http://spam.example.com/",
+            SERVER_NAME="spam.example.com")
+        self.checkAppURI("http://127.0.0.1/",
+            HTTP_HOST="127.0.0.1", SERVER_NAME="spam.example.com")
+        self.checkAppURI("https://127.0.0.1/", HTTPS="on")
+        self.checkAppURI("http://127.0.0.1:8000/", SERVER_PORT="8000",
+            HTTP_HOST=None)
+
+    def testReqURIs(self):
+        self.checkReqURI("http://127.0.0.1/")
+        self.checkReqURI("http://127.0.0.1/spam", SCRIPT_NAME="/spam")
+        self.checkReqURI("http://127.0.0.1/sp%E4m", SCRIPT_NAME="/sp\xe4m")
+        self.checkReqURI("http://127.0.0.1/spammity/spam",
+            SCRIPT_NAME="/spammity", PATH_INFO="/spam")
+        self.checkReqURI("http://127.0.0.1/spammity/sp%E4m",
+            SCRIPT_NAME="/spammity", PATH_INFO="/sp\xe4m")
+        self.checkReqURI("http://127.0.0.1/spammity/spam;ham",
+            SCRIPT_NAME="/spammity", PATH_INFO="/spam;ham")
+        self.checkReqURI("http://127.0.0.1/spammity/spam;cookie=1234,5678",
+            SCRIPT_NAME="/spammity", PATH_INFO="/spam;cookie=1234,5678")
+        self.checkReqURI("http://127.0.0.1/spammity/spam?say=ni",
+            SCRIPT_NAME="/spammity", PATH_INFO="/spam",QUERY_STRING="say=ni")
+        self.checkReqURI("http://127.0.0.1/spammity/spam?s%E4y=ni",
+            SCRIPT_NAME="/spammity", PATH_INFO="/spam",QUERY_STRING="s%E4y=ni")
+        self.checkReqURI("http://127.0.0.1/spammity/spam", 0,
+            SCRIPT_NAME="/spammity", PATH_INFO="/spam",QUERY_STRING="say=ni")
+
+    def testFileWrapper(self):
+        self.checkFW("xyz"*50, 120, ["xyz"*40,"xyz"*10])
+
+    def testHopByHop(self):
+        for hop in (
+            "Connection Keep-Alive Proxy-Authenticate Proxy-Authorization "
+            "TE Trailers Transfer-Encoding Upgrade"
+        ).split():
+            for alt in hop, hop.title(), hop.upper(), hop.lower():
+                self.assertTrue(util.is_hop_by_hop(alt))
+
+        # Not comprehensive, just a few random header names
+        for hop in (
+            "Accept Cache-Control Date Pragma Trailer Via Warning"
+        ).split():
+            for alt in hop, hop.title(), hop.upper(), hop.lower():
+                self.assertFalse(util.is_hop_by_hop(alt))
+
+class HeaderTests(TestCase):
+
+    def testMappingInterface(self):
+        test = [('x','y')]
+        self.assertEqual(len(Headers()), 0)
+        self.assertEqual(len(Headers([])),0)
+        self.assertEqual(len(Headers(test[:])),1)
+        self.assertEqual(Headers(test[:]).keys(), ['x'])
+        self.assertEqual(Headers(test[:]).values(), ['y'])
+        self.assertEqual(Headers(test[:]).items(), test)
+        self.assertIsNot(Headers(test).items(), test)  # must be copy!
+
+        h = Headers()
+        del h['foo']   # should not raise an error
+
+        h['Foo'] = 'bar'
+        for m in h.__contains__, h.get, h.get_all, h.__getitem__:
+            self.assertTrue(m('foo'))
+            self.assertTrue(m('Foo'))
+            self.assertTrue(m('FOO'))
+            self.assertFalse(m('bar'))
+
+        self.assertEqual(h['foo'],'bar')
+        h['foo'] = 'baz'
+        self.assertEqual(h['FOO'],'baz')
+        self.assertEqual(h.get_all('foo'),['baz'])
+
+        self.assertEqual(h.get("foo","whee"), "baz")
+        self.assertEqual(h.get("zoo","whee"), "whee")
+        self.assertEqual(h.setdefault("foo","whee"), "baz")
+        self.assertEqual(h.setdefault("zoo","whee"), "whee")
+        self.assertEqual(h["foo"],"baz")
+        self.assertEqual(h["zoo"],"whee")
+
+    def testRequireList(self):
+        self.assertRaises(TypeError, Headers, "foo")
+
+    def testExtras(self):
+        h = Headers()
+        self.assertEqual(str(h),'\r\n')
+
+        h.add_header('foo','bar',baz="spam")
+        self.assertEqual(h['foo'], 'bar; baz="spam"')
+        self.assertEqual(str(h),'foo: bar; baz="spam"\r\n\r\n')
+
+        h.add_header('Foo','bar',cheese=None)
+        self.assertEqual(h.get_all('foo'),
+            ['bar; baz="spam"', 'bar; cheese'])
+
+        self.assertEqual(str(h),
+            'foo: bar; baz="spam"\r\n'
+            'Foo: bar; cheese\r\n'
+            '\r\n'
+        )
+
+class ErrorHandler(BaseCGIHandler):
+    """Simple handler subclass for testing BaseHandler"""
+
+    # BaseHandler records the OS environment at import time, but envvars
+    # might have been changed later by other tests, which trips up
+    # HandlerTests.testEnviron().
+    os_environ = dict(os.environ.items())
+
+    def __init__(self,**kw):
+        setup_testing_defaults(kw)
+        BaseCGIHandler.__init__(
+            self, BytesIO(), BytesIO(), StringIO(), kw,
+            multithread=True, multiprocess=True
+        )
+
+class TestHandler(ErrorHandler):
+    """Simple handler subclass for testing BaseHandler, w/error passthru"""
+
+    def handle_error(self):
+        raise   # for testing, we want to see what's happening
+
+
+class HandlerTests(TestCase):
+    # testEnviron() can produce long error message
+    maxDiff = 80 * 50
+
+    def testEnviron(self):
+        os_environ = {
+            # very basic environment
+            'HOME': '/my/home',
+            'PATH': '/my/path',
+            'LANG': 'fr_FR.UTF-8',
+
+            # set some WSGI variables
+            'SCRIPT_NAME': 'test_script_name',
+            'SERVER_NAME': 'test_server_name',
+        }
+
+        with support.swap_attr(TestHandler, 'os_environ', os_environ):
+            # override X and HOME variables
+            handler = TestHandler(X="Y", HOME="/override/home")
+            handler.setup_environ()
+
+        # Check that wsgi_xxx attributes are copied to wsgi.xxx variables
+        # of handler.environ
+        for attr in ('version', 'multithread', 'multiprocess', 'run_once',
+                     'file_wrapper'):
+            self.assertEqual(getattr(handler, 'wsgi_' + attr),
+                             handler.environ['wsgi.' + attr])
+
+        # Test handler.environ as a dict
+        expected = {}
+        setup_testing_defaults(expected)
+        # Handler inherits os_environ variables which are not overriden
+        # by SimpleHandler.add_cgi_vars() (SimpleHandler.base_env)
+        for key, value in os_environ.items():
+            if key not in expected:
+                expected[key] = value
+        expected.update({
+            # X doesn't exist in os_environ
+            "X": "Y",
+            # HOME is overridden by TestHandler
+            'HOME': "/override/home",
+
+            # overridden by setup_testing_defaults()
+            "SCRIPT_NAME": "",
+            "SERVER_NAME": "127.0.0.1",
+
+            # set by BaseHandler.setup_environ()
+            'wsgi.input': handler.get_stdin(),
+            'wsgi.errors': handler.get_stderr(),
+            'wsgi.version': (1, 0),
+            'wsgi.run_once': False,
+            'wsgi.url_scheme': 'http',
+            'wsgi.multithread': True,
+            'wsgi.multiprocess': True,
+            'wsgi.file_wrapper': util.FileWrapper,
+        })
+        self.assertDictEqual(handler.environ, expected)
+
+    def testCGIEnviron(self):
+        h = BaseCGIHandler(None,None,None,{})
+        h.setup_environ()
+        for key in 'wsgi.url_scheme', 'wsgi.input', 'wsgi.errors':
+            self.assertIn(key, h.environ)
+
+    def testScheme(self):
+        h=TestHandler(HTTPS="on"); h.setup_environ()
+        self.assertEqual(h.environ['wsgi.url_scheme'],'https')
+        h=TestHandler(); h.setup_environ()
+        self.assertEqual(h.environ['wsgi.url_scheme'],'http')
+
+    def testAbstractMethods(self):
+        h = BaseHandler()
+        for name in [
+            '_flush','get_stdin','get_stderr','add_cgi_vars'
+        ]:
+            self.assertRaises(NotImplementedError, getattr(h,name))
+        self.assertRaises(NotImplementedError, h._write, "test")
+
+    def testContentLength(self):
+        # Demo one reason iteration is better than write()...  ;)
+
+        def trivial_app1(e,s):
+            s('200 OK',[])
+            return [e['wsgi.url_scheme'].encode('iso-8859-1')]
+
+        def trivial_app2(e,s):
+            s('200 OK',[])(e['wsgi.url_scheme'].encode('iso-8859-1'))
+            return []
+
+        def trivial_app3(e,s):
+            s('200 OK',[])
+            return ['\u0442\u0435\u0441\u0442'.encode("utf-8")]
+
+        def trivial_app4(e,s):
+            # Simulate a response to a HEAD request
+            s('200 OK',[('Content-Length', '12345')])
+            return []
+
+        h = TestHandler()
+        h.run(trivial_app1)
+        self.assertEqual(h.stdout.getvalue(),
+            ("Status: 200 OK\r\n"
+            "Content-Length: 4\r\n"
+            "\r\n"
+            "http").encode("iso-8859-1"))
+
+        h = TestHandler()
+        h.run(trivial_app2)
+        self.assertEqual(h.stdout.getvalue(),
+            ("Status: 200 OK\r\n"
+            "\r\n"
+            "http").encode("iso-8859-1"))
+
+        h = TestHandler()
+        h.run(trivial_app3)
+        self.assertEqual(h.stdout.getvalue(),
+            b'Status: 200 OK\r\n'
+            b'Content-Length: 8\r\n'
+            b'\r\n'
+            b'\xd1\x82\xd0\xb5\xd1\x81\xd1\x82')
+
+        h = TestHandler()
+        h.run(trivial_app4)
+        self.assertEqual(h.stdout.getvalue(),
+            b'Status: 200 OK\r\n'
+            b'Content-Length: 12345\r\n'
+            b'\r\n')
+
+    def testBasicErrorOutput(self):
+
+        def non_error_app(e,s):
+            s('200 OK',[])
+            return []
+
+        def error_app(e,s):
+            raise AssertionError("This should be caught by handler")
+
+        h = ErrorHandler()
+        h.run(non_error_app)
+        self.assertEqual(h.stdout.getvalue(),
+            ("Status: 200 OK\r\n"
+            "Content-Length: 0\r\n"
+            "\r\n").encode("iso-8859-1"))
+        self.assertEqual(h.stderr.getvalue(),"")
+
+        h = ErrorHandler()
+        h.run(error_app)
+        self.assertEqual(h.stdout.getvalue(),
+            ("Status: %s\r\n"
+            "Content-Type: text/plain\r\n"
+            "Content-Length: %d\r\n"
+            "\r\n" % (h.error_status,len(h.error_body))).encode('iso-8859-1')
+            + h.error_body)
+
+        self.assertIn("AssertionError", h.stderr.getvalue())
+
+    def testErrorAfterOutput(self):
+        MSG = b"Some output has been sent"
+        def error_app(e,s):
+            s("200 OK",[])(MSG)
+            raise AssertionError("This should be caught by handler")
+
+        h = ErrorHandler()
+        h.run(error_app)
+        self.assertEqual(h.stdout.getvalue(),
+            ("Status: 200 OK\r\n"
+            "\r\n".encode("iso-8859-1")+MSG))
+        self.assertIn("AssertionError", h.stderr.getvalue())
+
+    def testHeaderFormats(self):
+
+        def non_error_app(e,s):
+            s('200 OK',[])
+            return []
+
+        stdpat = (
+            r"HTTP/%s 200 OK\r\n"
+            r"Date: \w{3}, [ 0123]\d \w{3} \d{4} \d\d:\d\d:\d\d GMT\r\n"
+            r"%s" r"Content-Length: 0\r\n" r"\r\n"
+        )
+        shortpat = (
+            "Status: 200 OK\r\n" "Content-Length: 0\r\n" "\r\n"
+        ).encode("iso-8859-1")
+
+        for ssw in "FooBar/1.0", None:
+            sw = ssw and "Server: %s\r\n" % ssw or ""
+
+            for version in "1.0", "1.1":
+                for proto in "HTTP/0.9", "HTTP/1.0", "HTTP/1.1":
+
+                    h = TestHandler(SERVER_PROTOCOL=proto)
+                    h.origin_server = False
+                    h.http_version = version
+                    h.server_software = ssw
+                    h.run(non_error_app)
+                    self.assertEqual(shortpat,h.stdout.getvalue())
+
+                    h = TestHandler(SERVER_PROTOCOL=proto)
+                    h.origin_server = True
+                    h.http_version = version
+                    h.server_software = ssw
+                    h.run(non_error_app)
+                    if proto=="HTTP/0.9":
+                        self.assertEqual(h.stdout.getvalue(),b"")
+                    else:
+                        self.assertTrue(
+                            re.match((stdpat%(version,sw)).encode("iso-8859-1"),
+                                h.stdout.getvalue()),
+                            ((stdpat%(version,sw)).encode("iso-8859-1"),
+                                h.stdout.getvalue())
+                        )
+
+    def testBytesData(self):
+        def app(e, s):
+            s("200 OK", [
+                ("Content-Type", "text/plain; charset=utf-8"),
+                ])
+            return [b"data"]
+
+        h = TestHandler()
+        h.run(app)
+        self.assertEqual(b"Status: 200 OK\r\n"
+            b"Content-Type: text/plain; charset=utf-8\r\n"
+            b"Content-Length: 4\r\n"
+            b"\r\n"
+            b"data",
+            h.stdout.getvalue())
+
+    def testCloseOnError(self):
+        side_effects = {'close_called': False}
+        MSG = b"Some output has been sent"
+        def error_app(e,s):
+            s("200 OK",[])(MSG)
+            class CrashyIterable(object):
+                def __iter__(self):
+                    while True:
+                        yield b'blah'
+                        raise AssertionError("This should be caught by handler")
+                def close(self):
+                    side_effects['close_called'] = True
+            return CrashyIterable()
+
+        h = ErrorHandler()
+        h.run(error_app)
+        self.assertEqual(side_effects['close_called'], True)
+
+    def testPartialWrite(self):
+        written = bytearray()
+
+        class PartialWriter:
+            def write(self, b):
+                partial = b[:7]
+                written.extend(partial)
+                return len(partial)
+
+            def flush(self):
+                pass
+
+        environ = {"SERVER_PROTOCOL": "HTTP/1.0"}
+        h = SimpleHandler(BytesIO(), PartialWriter(), sys.stderr, environ)
+        msg = "should not do partial writes"
+        with self.assertWarnsRegex(DeprecationWarning, msg):
+            h.run(hello_app)
+        self.assertEqual(b"HTTP/1.0 200 OK\r\n"
+            b"Content-Type: text/plain\r\n"
+            b"Date: Mon, 05 Jun 2006 18:49:54 GMT\r\n"
+            b"Content-Length: 13\r\n"
+            b"\r\n"
+            b"Hello, world!",
+            written)
+
+    def testClientConnectionTerminations(self):
+        environ = {"SERVER_PROTOCOL": "HTTP/1.0"}
+        for exception in (
+            ConnectionAbortedError,
+            BrokenPipeError,
+            ConnectionResetError,
+        ):
+            with self.subTest(exception=exception):
+                class AbortingWriter:
+                    def write(self, b):
+                        raise exception
+
+                stderr = StringIO()
+                h = SimpleHandler(BytesIO(), AbortingWriter(), stderr, environ)
+                h.run(hello_app)
+
+                self.assertFalse(stderr.getvalue())
+
+    def testDontResetInternalStateOnException(self):
+        class CustomException(ValueError):
+            pass
+
+        # We are raising CustomException here to trigger an exception
+        # during the execution of SimpleHandler.finish_response(), so
+        # we can easily test that the internal state of the handler is
+        # preserved in case of an exception.
+        class AbortingWriter:
+            def write(self, b):
+                raise CustomException
+
+        stderr = StringIO()
+        environ = {"SERVER_PROTOCOL": "HTTP/1.0"}
+        h = SimpleHandler(BytesIO(), AbortingWriter(), stderr, environ)
+        h.run(hello_app)
+
+        self.assertIn("CustomException", stderr.getvalue())
+
+        # Test that the internal state of the handler is preserved.
+        self.assertIsNotNone(h.result)
+        self.assertIsNotNone(h.headers)
+        self.assertIsNotNone(h.status)
+        self.assertIsNotNone(h.environ)
+
+
+if __name__ == "__main__":
+    unittest.main()