diff --git a/changelog.d/3647.misc b/changelog.d/3647.misc
new file mode 100644
index 000000000000..dbc66dae6087
--- /dev/null
+++ b/changelog.d/3647.misc
@@ -0,0 +1 @@
+Tests now correctly execute on Python 3.
diff --git a/tests/handlers/test_typing.py b/tests/handlers/test_typing.py
index 2c263af1a3a0..f422cf3c5a5f 100644
--- a/tests/handlers/test_typing.py
+++ b/tests/handlers/test_typing.py
@@ -48,7 +48,9 @@ def _expect_edu(destination, edu_type, content, origin="test"):
 
 
 def _make_edu_json(origin, edu_type, content):
-    return json.dumps(_expect_edu("test", edu_type, content, origin=origin))
+    return json.dumps(
+        _expect_edu("test", edu_type, content, origin=origin)
+    ).encode('utf8')
 
 
 class TypingNotificationsTestCase(unittest.TestCase):
diff --git a/tests/rest/client/test_transactions.py b/tests/rest/client/test_transactions.py
index 34e68ae82fa4..d46c27e7e9f7 100644
--- a/tests/rest/client/test_transactions.py
+++ b/tests/rest/client/test_transactions.py
@@ -85,7 +85,7 @@ def cb():
             try:
                 yield self.cache.fetch_or_execute(self.mock_key, cb)
             except Exception as e:
-                self.assertEqual(e.message, "boo")
+                self.assertEqual(e.args[0], "boo")
             self.assertIs(LoggingContext.current_context(), test_context)
 
             res = yield self.cache.fetch_or_execute(self.mock_key, cb)
@@ -111,7 +111,7 @@ def cb():
             try:
                 yield self.cache.fetch_or_execute(self.mock_key, cb)
             except Exception as e:
-                self.assertEqual(e.message, "boo")
+                self.assertEqual(e.args[0], "boo")
             self.assertIs(LoggingContext.current_context(), test_context)
 
             res = yield self.cache.fetch_or_execute(self.mock_key, cb)
diff --git a/tests/rest/client/v1/test_admin.py b/tests/rest/client/v1/test_admin.py
index 8c90145601a6..fb28883d30c4 100644
--- a/tests/rest/client/v1/test_admin.py
+++ b/tests/rest/client/v1/test_admin.py
@@ -140,7 +140,7 @@ def test_register_incorrect_nonce(self):
                 "admin": True,
                 "mac": want_mac,
             }
-        ).encode('utf8')
+        )
         request, channel = make_request("POST", self.url, body.encode('utf8'))
         render(request, self.resource, self.clock)
 
@@ -168,7 +168,7 @@ def test_register_correct_nonce(self):
                 "admin": True,
                 "mac": want_mac,
             }
-        ).encode('utf8')
+        )
         request, channel = make_request("POST", self.url, body.encode('utf8'))
         render(request, self.resource, self.clock)
 
@@ -195,7 +195,7 @@ def test_nonce_reuse(self):
                 "admin": True,
                 "mac": want_mac,
             }
-        ).encode('utf8')
+        )
         request, channel = make_request("POST", self.url, body.encode('utf8'))
         render(request, self.resource, self.clock)
 
@@ -253,7 +253,7 @@ def nonce():
         self.assertEqual('Invalid username', channel.json_body["error"])
 
         # Must not have null bytes
-        body = json.dumps({"nonce": nonce(), "username": b"abcd\x00"})
+        body = json.dumps({"nonce": nonce(), "username": u"abcd\u0000"})
         request, channel = make_request("POST", self.url, body.encode('utf8'))
         render(request, self.resource, self.clock)
 
@@ -289,7 +289,7 @@ def nonce():
         self.assertEqual('Invalid password', channel.json_body["error"])
 
         # Must not have null bytes
-        body = json.dumps({"nonce": nonce(), "username": "a", "password": b"abcd\x00"})
+        body = json.dumps({"nonce": nonce(), "username": "a", "password": u"abcd\u0000"})
         request, channel = make_request("POST", self.url, body.encode('utf8'))
         render(request, self.resource, self.clock)
 
diff --git a/tests/rest/client/v1/test_profile.py b/tests/rest/client/v1/test_profile.py
index d71cc8e0db73..0516ce3cfbd2 100644
--- a/tests/rest/client/v1/test_profile.py
+++ b/tests/rest/client/v1/test_profile.py
@@ -80,7 +80,7 @@ def test_set_my_name(self):
         (code, response) = yield self.mock_resource.trigger(
             "PUT",
             "/profile/%s/displayname" % (myid),
-            '{"displayname": "Frank Jr."}'
+            b'{"displayname": "Frank Jr."}'
         )
 
         self.assertEquals(200, code)
@@ -95,7 +95,7 @@ def test_set_my_name_noauth(self):
 
         (code, response) = yield self.mock_resource.trigger(
             "PUT", "/profile/%s/displayname" % ("@4567:test"),
-            '{"displayname": "Frank Jr."}'
+            b'{"displayname": "Frank Jr."}'
         )
 
         self.assertTrue(
@@ -122,7 +122,7 @@ def test_set_other_name(self):
 
         (code, response) = yield self.mock_resource.trigger(
             "PUT", "/profile/%s/displayname" % ("@opaque:elsewhere"),
-            '{"displayname":"bob"}'
+            b'{"displayname":"bob"}'
         )
 
         self.assertTrue(
@@ -151,7 +151,7 @@ def test_set_my_avatar(self):
         (code, response) = yield self.mock_resource.trigger(
             "PUT",
             "/profile/%s/avatar_url" % (myid),
-            '{"avatar_url": "http://my.server/pic.gif"}'
+            b'{"avatar_url": "http://my.server/pic.gif"}'
         )
 
         self.assertEquals(200, code)
diff --git a/tests/rest/client/v1/utils.py b/tests/rest/client/v1/utils.py
index 41de8e0762ec..e3bc5f378d22 100644
--- a/tests/rest/client/v1/utils.py
+++ b/tests/rest/client/v1/utils.py
@@ -105,7 +105,7 @@ def register(self, user_id):
                 "password": "test",
                 "type": "m.login.password"
             }))
-        self.assertEquals(200, code)
+        self.assertEquals(200, code, msg=response)
         defer.returnValue(response)
 
     @defer.inlineCallbacks
@@ -149,14 +149,14 @@ class RestHelper(object):
     def create_room_as(self, room_creator, is_public=True, tok=None):
         temp_id = self.auth_user_id
         self.auth_user_id = room_creator
-        path = b"/_matrix/client/r0/createRoom"
+        path = "/_matrix/client/r0/createRoom"
         content = {}
         if not is_public:
             content["visibility"] = "private"
         if tok:
-            path = path + b"?access_token=%s" % tok.encode('ascii')
+            path = path + "?access_token=%s" % tok
 
-        request, channel = make_request(b"POST", path, json.dumps(content).encode('utf8'))
+        request, channel = make_request("POST", path, json.dumps(content).encode('utf8'))
         request.render(self.resource)
         wait_until_result(self.hs.get_reactor(), channel)
 
@@ -205,7 +205,7 @@ def change_membership(self, room, src, targ, membership, tok=None, expect_code=2
         data = {"membership": membership}
 
         request, channel = make_request(
-            b"PUT", path.encode('ascii'), json.dumps(data).encode('utf8')
+            "PUT", path, json.dumps(data).encode('utf8')
         )
 
         request.render(self.resource)
diff --git a/tests/rest/client/v2_alpha/test_filter.py b/tests/rest/client/v2_alpha/test_filter.py
index e890f0feac46..de33b10a5f5e 100644
--- a/tests/rest/client/v2_alpha/test_filter.py
+++ b/tests/rest/client/v2_alpha/test_filter.py
@@ -33,7 +33,7 @@
 
 class FilterTestCase(unittest.TestCase):
 
-    USER_ID = b"@apple:test"
+    USER_ID = "@apple:test"
     EXAMPLE_FILTER = {"room": {"timeline": {"types": ["m.room.message"]}}}
     EXAMPLE_FILTER_JSON = b'{"room": {"timeline": {"types": ["m.room.message"]}}}'
     TO_REGISTER = [filter]
@@ -72,8 +72,8 @@ def get_user_by_req(request, allow_guest=False, rights="access"):
 
     def test_add_filter(self):
         request, channel = make_request(
-            b"POST",
-            b"/_matrix/client/r0/user/%s/filter" % (self.USER_ID),
+            "POST",
+            "/_matrix/client/r0/user/%s/filter" % (self.USER_ID),
             self.EXAMPLE_FILTER_JSON,
         )
         request.render(self.resource)
@@ -87,8 +87,8 @@ def test_add_filter(self):
 
     def test_add_filter_for_other_user(self):
         request, channel = make_request(
-            b"POST",
-            b"/_matrix/client/r0/user/%s/filter" % (b"@watermelon:test"),
+            "POST",
+            "/_matrix/client/r0/user/%s/filter" % ("@watermelon:test"),
             self.EXAMPLE_FILTER_JSON,
         )
         request.render(self.resource)
@@ -101,8 +101,8 @@ def test_add_filter_non_local_user(self):
         _is_mine = self.hs.is_mine
         self.hs.is_mine = lambda target_user: False
         request, channel = make_request(
-            b"POST",
-            b"/_matrix/client/r0/user/%s/filter" % (self.USER_ID),
+            "POST",
+            "/_matrix/client/r0/user/%s/filter" % (self.USER_ID),
             self.EXAMPLE_FILTER_JSON,
         )
         request.render(self.resource)
@@ -119,7 +119,7 @@ def test_get_filter(self):
         self.clock.advance(1)
         filter_id = filter_id.result
         request, channel = make_request(
-            b"GET", b"/_matrix/client/r0/user/%s/filter/%s" % (self.USER_ID, filter_id)
+            "GET", "/_matrix/client/r0/user/%s/filter/%s" % (self.USER_ID, filter_id)
         )
         request.render(self.resource)
         wait_until_result(self.clock, channel)
@@ -129,7 +129,7 @@ def test_get_filter(self):
 
     def test_get_filter_non_existant(self):
         request, channel = make_request(
-            b"GET", "/_matrix/client/r0/user/%s/filter/12382148321" % (self.USER_ID)
+            "GET", "/_matrix/client/r0/user/%s/filter/12382148321" % (self.USER_ID)
         )
         request.render(self.resource)
         wait_until_result(self.clock, channel)
@@ -141,7 +141,7 @@ def test_get_filter_non_existant(self):
     # in errors.py
     def test_get_filter_invalid_id(self):
         request, channel = make_request(
-            b"GET", "/_matrix/client/r0/user/%s/filter/foobar" % (self.USER_ID)
+            "GET", "/_matrix/client/r0/user/%s/filter/foobar" % (self.USER_ID)
         )
         request.render(self.resource)
         wait_until_result(self.clock, channel)
@@ -151,7 +151,7 @@ def test_get_filter_invalid_id(self):
     # No ID also returns an invalid_id error
     def test_get_filter_no_id(self):
         request, channel = make_request(
-            b"GET", "/_matrix/client/r0/user/%s/filter/" % (self.USER_ID)
+            "GET", "/_matrix/client/r0/user/%s/filter/" % (self.USER_ID)
         )
         request.render(self.resource)
         wait_until_result(self.clock, channel)
diff --git a/tests/rest/client/v2_alpha/test_register.py b/tests/rest/client/v2_alpha/test_register.py
index e004d8fc73d9..f6293f11a871 100644
--- a/tests/rest/client/v2_alpha/test_register.py
+++ b/tests/rest/client/v2_alpha/test_register.py
@@ -81,7 +81,7 @@ def test_POST_appservice_registration_valid(self):
             "access_token": token,
             "home_server": self.hs.hostname,
         }
-        self.assertDictContainsSubset(det_data, json.loads(channel.result["body"]))
+        self.assertDictContainsSubset(det_data, channel.json_body)
 
     def test_POST_appservice_registration_invalid(self):
         self.appservice = None  # no application service exists
@@ -102,7 +102,7 @@ def test_POST_bad_password(self):
 
         self.assertEquals(channel.result["code"], b"400", channel.result)
         self.assertEquals(
-            json.loads(channel.result["body"])["error"], "Invalid password"
+            channel.json_body["error"], "Invalid password"
         )
 
     def test_POST_bad_username(self):
@@ -113,7 +113,7 @@ def test_POST_bad_username(self):
 
         self.assertEquals(channel.result["code"], b"400", channel.result)
         self.assertEquals(
-            json.loads(channel.result["body"])["error"], "Invalid username"
+            channel.json_body["error"], "Invalid username"
         )
 
     def test_POST_user_valid(self):
@@ -140,7 +140,7 @@ def test_POST_user_valid(self):
             "device_id": device_id,
         }
         self.assertEquals(channel.result["code"], b"200", channel.result)
-        self.assertDictContainsSubset(det_data, json.loads(channel.result["body"]))
+        self.assertDictContainsSubset(det_data, channel.json_body)
         self.auth_handler.get_login_tuple_for_user_id(
             user_id, device_id=device_id, initial_device_display_name=None
         )
@@ -158,7 +158,7 @@ def test_POST_disabled_registration(self):
 
         self.assertEquals(channel.result["code"], b"403", channel.result)
         self.assertEquals(
-            json.loads(channel.result["body"])["error"],
+            channel.json_body["error"],
             "Registration has been disabled",
         )
 
@@ -178,7 +178,7 @@ def test_POST_guest_registration(self):
             "device_id": "guest_device",
         }
         self.assertEquals(channel.result["code"], b"200", channel.result)
-        self.assertDictContainsSubset(det_data, json.loads(channel.result["body"]))
+        self.assertDictContainsSubset(det_data, channel.json_body)
 
     def test_POST_disabled_guest_registration(self):
         self.hs.config.allow_guest_access = False
@@ -189,5 +189,5 @@ def test_POST_disabled_guest_registration(self):
 
         self.assertEquals(channel.result["code"], b"403", channel.result)
         self.assertEquals(
-            json.loads(channel.result["body"])["error"], "Guest access is disabled"
+            channel.json_body["error"], "Guest access is disabled"
         )
diff --git a/tests/rest/client/v2_alpha/test_sync.py b/tests/rest/client/v2_alpha/test_sync.py
index 03ec3993b2df..bafc0d1df07d 100644
--- a/tests/rest/client/v2_alpha/test_sync.py
+++ b/tests/rest/client/v2_alpha/test_sync.py
@@ -32,7 +32,7 @@
 
 class FilterTestCase(unittest.TestCase):
 
-    USER_ID = b"@apple:test"
+    USER_ID = "@apple:test"
     TO_REGISTER = [sync]
 
     def setUp(self):
@@ -68,7 +68,7 @@ def get_user_by_req(request, allow_guest=False, rights="access"):
             r.register_servlets(self.hs, self.resource)
 
     def test_sync_argless(self):
-        request, channel = make_request(b"GET", b"/_matrix/client/r0/sync")
+        request, channel = make_request("GET", "/_matrix/client/r0/sync")
         request.render(self.resource)
         wait_until_result(self.clock, channel)
 
diff --git a/tests/server.py b/tests/server.py
index c611dd6059dd..e249668d2104 100644
--- a/tests/server.py
+++ b/tests/server.py
@@ -11,6 +11,7 @@
 from twisted.test.proto_helpers import MemoryReactorClock
 
 from synapse.http.site import SynapseRequest
+from synapse.util import Clock
 
 from tests.utils import setup_test_homeserver as _sth
 
@@ -28,7 +29,13 @@ class FakeChannel(object):
     def json_body(self):
         if not self.result:
             raise Exception("No result yet.")
-        return json.loads(self.result["body"])
+        return json.loads(self.result["body"].decode('utf8'))
+
+    @property
+    def code(self):
+        if not self.result:
+            raise Exception("No result yet.")
+        return int(self.result["code"])
 
     def writeHeaders(self, version, code, reason, headers):
         self.result["version"] = version
@@ -79,11 +86,16 @@ def make_request(method, path, content=b""):
     Make a web request using the given method and path, feed it the
     content, and return the Request and the Channel underneath.
     """
+    if not isinstance(method, bytes):
+        method = method.encode('ascii')
+
+    if not isinstance(path, bytes):
+        path = path.encode('ascii')
 
     # Decorate it to be the full path
     if not path.startswith(b"/_matrix"):
         path = b"/_matrix/client/r0/" + path
-        path = path.replace("//", "/")
+        path = path.replace(b"//", b"/")
 
     if isinstance(content, text_type):
         content = content.encode('utf8')
@@ -191,3 +203,9 @@ def _(res):
     clock.threadpool = ThreadPool()
     pool.threadpool = ThreadPool()
     return d
+
+
+def get_clock():
+    clock = ThreadedMemoryReactorClock()
+    hs_clock = Clock(clock)
+    return (clock, hs_clock)
diff --git a/tests/storage/test_event_federation.py b/tests/storage/test_event_federation.py
index 30683e7888ed..69412c5aadd8 100644
--- a/tests/storage/test_event_federation.py
+++ b/tests/storage/test_event_federation.py
@@ -49,7 +49,7 @@ def insert_event(txn, i):
                 'INSERT INTO event_reference_hashes '
                 '(event_id, algorithm, hash) '
                 "VALUES (?, 'sha256', ?)"
-            ), (event_id, 'ffff'))
+            ), (event_id, b'ffff'))
 
         for i in range(0, 11):
             yield self.store.runInteraction("insert", insert_event, i)
diff --git a/tests/storage/test_state.py b/tests/storage/test_state.py
index 7a76d67b8c8b..f7871cd42611 100644
--- a/tests/storage/test_state.py
+++ b/tests/storage/test_state.py
@@ -176,7 +176,7 @@ def test_get_state_for_event(self):
 
         room_id = self.room.to_string()
         group_ids = yield self.store.get_state_groups_ids(room_id, [e5.event_id])
-        group = group_ids.keys()[0]
+        group = list(group_ids.keys())[0]
 
         # test _get_some_state_from_cache correctly filters out members with types=[]
         (state_dict, is_all) = yield self.store._get_some_state_from_cache(
diff --git a/tests/test_server.py b/tests/test_server.py
index 7e063c029096..fc396226ea27 100644
--- a/tests/test_server.py
+++ b/tests/test_server.py
@@ -1,4 +1,3 @@
-import json
 import re
 
 from twisted.internet.defer import Deferred
@@ -104,9 +103,8 @@ def _callback(request, **kwargs):
         request.render(res)
 
         self.assertEqual(channel.result["code"], b'403')
-        reply_body = json.loads(channel.result["body"])
-        self.assertEqual(reply_body["error"], "Forbidden!!one!")
-        self.assertEqual(reply_body["errcode"], "M_FORBIDDEN")
+        self.assertEqual(channel.json_body["error"], "Forbidden!!one!")
+        self.assertEqual(channel.json_body["errcode"], "M_FORBIDDEN")
 
     def test_no_handler(self):
         """
@@ -126,6 +124,5 @@ def _callback(request, **kwargs):
         request.render(res)
 
         self.assertEqual(channel.result["code"], b'400')
-        reply_body = json.loads(channel.result["body"])
-        self.assertEqual(reply_body["error"], "Unrecognized request")
-        self.assertEqual(reply_body["errcode"], "M_UNRECOGNIZED")
+        self.assertEqual(channel.json_body["error"], "Unrecognized request")
+        self.assertEqual(channel.json_body["errcode"], "M_UNRECOGNIZED")
diff --git a/tests/utils.py b/tests/utils.py
index 9bff3ff3b9b5..f95b8686982b 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -146,8 +146,9 @@ def setup_test_homeserver(name="test", datastore=None, config=None, reactor=None
     # Need to let the HS build an auth handler and then mess with it
     # because AuthHandler's constructor requires the HS, so we can't make one
     # beforehand and pass it in to the HS's constructor (chicken / egg)
-    hs.get_auth_handler().hash = lambda p: hashlib.md5(p).hexdigest()
-    hs.get_auth_handler().validate_hash = lambda p, h: hashlib.md5(p).hexdigest() == h
+    hs.get_auth_handler().hash = lambda p: hashlib.md5(p.encode('utf8')).hexdigest()
+    hs.get_auth_handler().validate_hash = lambda p, h: hashlib.md5(
+        p.encode('utf8')).hexdigest() == h
 
     fed = kargs.get("resource_for_federation", None)
     if fed:
@@ -220,8 +221,8 @@ def trigger(self, http_method, path, content, mock_request, federation_auth=Fals
         mock_content.configure_mock(**config)
         mock_request.content = mock_content
 
-        mock_request.method = http_method
-        mock_request.uri = path
+        mock_request.method = http_method.encode('ascii')
+        mock_request.uri = path.encode('ascii')
 
         mock_request.getClientIP.return_value = "-"