Merge tag 'v1.74.0rc1' into rei/uvloop github/rei/uvloop rei/uvloop

Synapse 1.74.0rc1 (2022-12-13)
==============================

Features
--------

- Improve user search for international display names. ([\#14464](https://github.com/matrix-org/synapse/issues/14464))
- Stop using deprecated `keyIds` parameter when calling `/_matrix/key/v2/server`. ([\#14490](https://github.com/matrix-org/synapse/issues/14490), [\#14525](https://github.com/matrix-org/synapse/issues/14525))
- Add new `push.enabled` config option to allow opting out of push notification calculation. ([\#14551](https://github.com/matrix-org/synapse/issues/14551), [\#14619](https://github.com/matrix-org/synapse/issues/14619))
- Advertise support for Matrix 1.5 on `/_matrix/client/versions`. ([\#14576](https://github.com/matrix-org/synapse/issues/14576))
- Improve opentracing and logging for to-device message handling. ([\#14598](https://github.com/matrix-org/synapse/issues/14598))
- Allow selecting "prejoin" events by state keys in addition to event types. ([\#14642](https://github.com/matrix-org/synapse/issues/14642))

Bugfixes
--------

- Fix a long-standing bug where a device list update might not be sent to clients in certain circumstances. ([\#14435](https://github.com/matrix-org/synapse/issues/14435), [\#14592](https://github.com/matrix-org/synapse/issues/14592), [\#14604](https://github.com/matrix-org/synapse/issues/14604))
- Suppress a spurious warning when `POST /rooms/<room_id>/<membership>/`, `POST /join/<room_id_or_alias`, or the unspecced `PUT /join/<room_id_or_alias>/<txn_id>` receive an empty HTTP request body. ([\#14600](https://github.com/matrix-org/synapse/issues/14600))
- Return spec-compliant JSON errors when unknown endpoints are requested. ([\#14620](https://github.com/matrix-org/synapse/issues/14620), [\#14621](https://github.com/matrix-org/synapse/issues/14621))
- Update html templates to load images over HTTPS. Contributed by @ashfame. ([\#14625](https://github.com/matrix-org/synapse/issues/14625))
- Fix a long-standing bug where the user directory would return 1 more row than requested. ([\#14631](https://github.com/matrix-org/synapse/issues/14631))
- Reject invalid read receipt requests with empty room or event IDs. Contributed by Nick @ Beeper (@fizzadar). ([\#14632](https://github.com/matrix-org/synapse/issues/14632))
- Fix a bug introduced in Synapse 1.67.0 where not specifying a config file or a server URL would lead to the `register_new_matrix_user` script failing. ([\#14637](https://github.com/matrix-org/synapse/issues/14637))
- Fix a long-standing bug where the user directory and room/user stats might be out of sync. ([\#14639](https://github.com/matrix-org/synapse/issues/14639), [\#14643](https://github.com/matrix-org/synapse/issues/14643))
- Fix a bug introduced in Synapse 1.72.0 where the background updates to add non-thread unique indexes on receipts would fail if they were previously interrupted. ([\#14650](https://github.com/matrix-org/synapse/issues/14650))
- Improve validation of field size limits in events. ([\#14664](https://github.com/matrix-org/synapse/issues/14664))
- Fix bugs introduced in Synapse 1.55.0 and 1.69.0 where application services would not be notified of events in the correct rooms, due to stale caches. ([\#14670](https://github.com/matrix-org/synapse/issues/14670))

Improved Documentation
----------------------

- Update worker settings for `pusher` and `federation_sender` functionality. ([\#14493](https://github.com/matrix-org/synapse/issues/14493))
- Add links to third party package repositories, and point to the bug which highlights Ubuntu's out-of-date packages. ([\#14517](https://github.com/matrix-org/synapse/issues/14517))
- Remove old, incorrect minimum postgres version note and replace with a link to the [Dependency Deprecation Policy](https://matrix-org.github.io/synapse/v1.73/deprecation_policy.html). ([\#14590](https://github.com/matrix-org/synapse/issues/14590))
- Add Single-Sign On setup instructions for Mastodon-based instances. ([\#14594](https://github.com/matrix-org/synapse/issues/14594))
- Change `turn_allow_guests` example value to lowercase `true`. ([\#14634](https://github.com/matrix-org/synapse/issues/14634))

Internal Changes
----------------

- Optimise push badge count calculations. Contributed by Nick @ Beeper (@fizzadar). ([\#14255](https://github.com/matrix-org/synapse/issues/14255))
- Faster remote room joins: stream the un-partial-stating of rooms over replication. ([\#14473](https://github.com/matrix-org/synapse/issues/14473), [\#14474](https://github.com/matrix-org/synapse/issues/14474))
- Share the `ClientRestResource` for both workers and the main process. ([\#14528](https://github.com/matrix-org/synapse/issues/14528))
- Add `--editable` flag to `complement.sh` which uses an editable install of Synapse for faster turn-around times whilst developing iteratively. ([\#14548](https://github.com/matrix-org/synapse/issues/14548))
- Faster joins: use servers list approximation to send read receipts when in partial state instead of waiting for the full state of the room. ([\#14549](https://github.com/matrix-org/synapse/issues/14549))
- Modernize unit tests configuration related to workers. ([\#14568](https://github.com/matrix-org/synapse/issues/14568))
- Bump jsonschema from 4.17.0 to 4.17.3. ([\#14591](https://github.com/matrix-org/synapse/issues/14591))
- Fix Rust lint CI. ([\#14602](https://github.com/matrix-org/synapse/issues/14602))
- Bump JasonEtco/create-an-issue from 2.5.0 to 2.8.1. ([\#14607](https://github.com/matrix-org/synapse/issues/14607))
- Alter some unit test environment parameters to decrease time spent running tests. ([\#14610](https://github.com/matrix-org/synapse/issues/14610))
- Switch to Go recommended installation method for `gotestfmt` template in CI. ([\#14611](https://github.com/matrix-org/synapse/issues/14611))
- Bump phonenumbers from 8.13.0 to 8.13.1. ([\#14612](https://github.com/matrix-org/synapse/issues/14612))
- Bump types-setuptools from 65.5.0.3 to 65.6.0.1. ([\#14613](https://github.com/matrix-org/synapse/issues/14613))
- Bump twine from 4.0.1 to 4.0.2. ([\#14614](https://github.com/matrix-org/synapse/issues/14614))
- Bump types-requests from 2.28.11.2 to 2.28.11.5. ([\#14615](https://github.com/matrix-org/synapse/issues/14615))
- Bump cryptography from 38.0.3 to 38.0.4. ([\#14616](https://github.com/matrix-org/synapse/issues/14616))
- Remove useless cargo install with apt from Dockerfile. ([\#14636](https://github.com/matrix-org/synapse/issues/14636))
- Bump certifi from 2021.10.8 to 2022.12.7. ([\#14645](https://github.com/matrix-org/synapse/issues/14645))
- Bump flake8-bugbear from 22.10.27 to 22.12.6. ([\#14656](https://github.com/matrix-org/synapse/issues/14656))
- Bump packaging from 21.3 to 22.0. ([\#14657](https://github.com/matrix-org/synapse/issues/14657))
- Bump types-pillow from 9.3.0.1 to 9.3.0.4. ([\#14658](https://github.com/matrix-org/synapse/issues/14658))
- Bump serde from 1.0.148 to 1.0.150. ([\#14659](https://github.com/matrix-org/synapse/issues/14659))
- Bump phonenumbers from 8.13.1 to 8.13.2. ([\#14660](https://github.com/matrix-org/synapse/issues/14660))
- Bump authlib from 1.1.0 to 1.2.0. ([\#14661](https://github.com/matrix-org/synapse/issues/14661))
- Move `StateFilter` to `synapse.types`. ([\#14668](https://github.com/matrix-org/synapse/issues/14668))
- Improve type hints. ([\#14597](https://github.com/matrix-org/synapse/issues/14597), [\#14646](https://github.com/matrix-org/synapse/issues/14646), [\#14671](https://github.com/matrix-org/synapse/issues/14671))

15 files changed, 1547 insertions, 330 deletions

diff --git a/tests/rest/admin/test_device.py b/tests/rest/admin/test_device.py
index d52aee8f92..03f2112b07 100644
--- a/tests/rest/admin/test_device.py
+++ b/tests/rest/admin/test_device.py
@@ -19,6 +19,7 @@ from twisted.test.proto_helpers import MemoryReactor
 
 import synapse.rest.admin
 from synapse.api.errors import Codes
+from synapse.handlers.device import DeviceHandler
 from synapse.rest.client import login
 from synapse.server import HomeServer
 from synapse.util import Clock
@@ -34,7 +35,9 @@ class DeviceRestTestCase(unittest.HomeserverTestCase):
     ]
 
     def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
-        self.handler = hs.get_device_handler()
+        handler = hs.get_device_handler()
+        assert isinstance(handler, DeviceHandler)
+        self.handler = handler
 
         self.admin_user = self.register_user("admin", "pass", admin=True)
         self.admin_user_tok = self.login("admin", "pass")
diff --git a/tests/rest/admin/test_room.py b/tests/rest/admin/test_room.py
index d156be82b0..e0f5d54aba 100644
--- a/tests/rest/admin/test_room.py
+++ b/tests/rest/admin/test_room.py
@@ -1857,6 +1857,46 @@ class RoomMessagesTestCase(unittest.HomeserverTestCase):
         self.assertIn("chunk", channel.json_body)
         self.assertIn("end", channel.json_body)
 
+    def test_room_messages_backward(self) -> None:
+        """Test room messages can be retrieved by an admin that isn't in the room."""
+        latest_event_id = self.helper.send(
+            self.room_id, body="message 1", tok=self.user_tok
+        )["event_id"]
+
+        # Check that we get the first and second message when querying /messages.
+        channel = self.make_request(
+            "GET",
+            "/_synapse/admin/v1/rooms/%s/messages?dir=b" % (self.room_id,),
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+
+        chunk = channel.json_body["chunk"]
+        self.assertEqual(len(chunk), 6, [event["content"] for event in chunk])
+
+        # in backwards, this is the first event
+        self.assertEqual(chunk[0]["event_id"], latest_event_id)
+
+    def test_room_messages_forward(self) -> None:
+        """Test room messages can be retrieved by an admin that isn't in the room."""
+        latest_event_id = self.helper.send(
+            self.room_id, body="message 1", tok=self.user_tok
+        )["event_id"]
+
+        # Check that we get the first and second message when querying /messages.
+        channel = self.make_request(
+            "GET",
+            "/_synapse/admin/v1/rooms/%s/messages?dir=f" % (self.room_id,),
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+
+        chunk = channel.json_body["chunk"]
+        self.assertEqual(len(chunk), 6, [event["content"] for event in chunk])
+
+        # in forward, this is the last event
+        self.assertEqual(chunk[5]["event_id"], latest_event_id)
+
     def test_room_messages_purge(self) -> None:
         """Test room messages can be retrieved by an admin that isn't in the room."""
         store = self.hs.get_datastores().main
diff --git a/tests/rest/admin/test_user.py b/tests/rest/admin/test_user.py
index 4c1ce33463..5c1ced355f 100644
--- a/tests/rest/admin/test_user.py
+++ b/tests/rest/admin/test_user.py
@@ -31,7 +31,7 @@ from synapse.api.room_versions import RoomVersions
 from synapse.rest.client import devices, login, logout, profile, register, room, sync
 from synapse.rest.media.v1.filepath import MediaFilePaths
 from synapse.server import HomeServer
-from synapse.types import JsonDict, UserID
+from synapse.types import JsonDict, UserID, create_requester
 from synapse.util import Clock
 
 from tests import unittest
@@ -41,14 +41,12 @@ from tests.unittest import override_config
 
 
 class UserRegisterTestCase(unittest.HomeserverTestCase):
-
     servlets = [
         synapse.rest.admin.register_servlets_for_client_rest_resource,
         profile.register_servlets,
     ]
 
     def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
-
         self.url = "/_synapse/admin/v1/register"
 
         self.registration_handler = Mock()
@@ -446,7 +444,6 @@ class UserRegisterTestCase(unittest.HomeserverTestCase):
 
 
 class UsersListTestCase(unittest.HomeserverTestCase):
-
     servlets = [
         synapse.rest.admin.register_servlets,
         login.register_servlets,
@@ -924,6 +921,36 @@ class UsersListTestCase(unittest.HomeserverTestCase):
         self.assertEqual(1, len(non_admin_user_ids), non_admin_user_ids)
         self.assertEqual(not_approved_user, non_admin_user_ids[0])
 
+    def test_erasure_status(self) -> None:
+        # Create a new user.
+        user_id = self.register_user("eraseme", "eraseme")
+
+        # They should appear in the list users API, marked as not erased.
+        channel = self.make_request(
+            "GET",
+            self.url + "?deactivated=true",
+            access_token=self.admin_user_tok,
+        )
+        users = {user["name"]: user for user in channel.json_body["users"]}
+        self.assertIs(users[user_id]["erased"], False)
+
+        # Deactivate that user, requesting erasure.
+        deactivate_account_handler = self.hs.get_deactivate_account_handler()
+        self.get_success(
+            deactivate_account_handler.deactivate_account(
+                user_id, erase_data=True, requester=create_requester(user_id)
+            )
+        )
+
+        # Repeat the list users query. They should now be marked as erased.
+        channel = self.make_request(
+            "GET",
+            self.url + "?deactivated=true",
+            access_token=self.admin_user_tok,
+        )
+        users = {user["name"]: user for user in channel.json_body["users"]}
+        self.assertIs(users[user_id]["erased"], True)
+
     def _order_test(
         self,
         expected_user_list: List[str],
@@ -1078,7 +1105,6 @@ class UserDevicesTestCase(unittest.HomeserverTestCase):
 
 
 class DeactivateAccountTestCase(unittest.HomeserverTestCase):
-
     servlets = [
         synapse.rest.admin.register_servlets,
         login.register_servlets,
@@ -1195,6 +1221,7 @@ class DeactivateAccountTestCase(unittest.HomeserverTestCase):
         self.assertEqual("foo@bar.com", channel.json_body["threepids"][0]["address"])
         self.assertEqual("mxc://servername/mediaid", channel.json_body["avatar_url"])
         self.assertEqual("User1", channel.json_body["displayname"])
+        self.assertFalse(channel.json_body["erased"])
 
         # Deactivate and erase user
         channel = self.make_request(
@@ -1219,6 +1246,7 @@ class DeactivateAccountTestCase(unittest.HomeserverTestCase):
         self.assertEqual(0, len(channel.json_body["threepids"]))
         self.assertIsNone(channel.json_body["avatar_url"])
         self.assertIsNone(channel.json_body["displayname"])
+        self.assertTrue(channel.json_body["erased"])
 
         self._is_erased("@user:test", True)
 
@@ -1350,7 +1378,6 @@ class DeactivateAccountTestCase(unittest.HomeserverTestCase):
 
 
 class UserRestTestCase(unittest.HomeserverTestCase):
-
     servlets = [
         synapse.rest.admin.register_servlets,
         login.register_servlets,
@@ -2757,6 +2784,7 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         self.assertIn("avatar_url", content)
         self.assertIn("admin", content)
         self.assertIn("deactivated", content)
+        self.assertIn("erased", content)
         self.assertIn("shadow_banned", content)
         self.assertIn("creation_ts", content)
         self.assertIn("appservice_id", content)
@@ -2770,7 +2798,6 @@ class UserRestTestCase(unittest.HomeserverTestCase):
 
 
 class UserMembershipRestTestCase(unittest.HomeserverTestCase):
-
     servlets = [
         synapse.rest.admin.register_servlets,
         login.register_servlets,
@@ -2927,7 +2954,6 @@ class UserMembershipRestTestCase(unittest.HomeserverTestCase):
 
 
 class PushersRestTestCase(unittest.HomeserverTestCase):
-
     servlets = [
         synapse.rest.admin.register_servlets,
         login.register_servlets,
@@ -3056,7 +3082,6 @@ class PushersRestTestCase(unittest.HomeserverTestCase):
 
 
 class UserMediaRestTestCase(unittest.HomeserverTestCase):
-
     servlets = [
         synapse.rest.admin.register_servlets,
         login.register_servlets,
@@ -3848,7 +3873,6 @@ class UserTokenRestTestCase(unittest.HomeserverTestCase):
     ],
 )
 class WhoisRestTestCase(unittest.HomeserverTestCase):
-
     servlets = [
         synapse.rest.admin.register_servlets,
         login.register_servlets,
@@ -3928,7 +3952,6 @@ class WhoisRestTestCase(unittest.HomeserverTestCase):
 
 
 class ShadowBanRestTestCase(unittest.HomeserverTestCase):
-
     servlets = [
         synapse.rest.admin.register_servlets,
         login.register_servlets,
@@ -3971,7 +3994,7 @@ class ShadowBanRestTestCase(unittest.HomeserverTestCase):
         """
         Tests that shadow-banning for a user that is not a local returns a 400
         """
-        url = "/_synapse/admin/v1/whois/@unknown_person:unknown_domain"
+        url = "/_synapse/admin/v1/users/@unknown_person:unknown_domain/shadow_ban"
 
         channel = self.make_request(method, url, access_token=self.admin_user_tok)
         self.assertEqual(400, channel.code, msg=channel.json_body)
@@ -4009,7 +4032,6 @@ class ShadowBanRestTestCase(unittest.HomeserverTestCase):
 
 
 class RateLimitTestCase(unittest.HomeserverTestCase):
-
     servlets = [
         synapse.rest.admin.register_servlets,
         login.register_servlets,
@@ -4235,7 +4257,6 @@ class RateLimitTestCase(unittest.HomeserverTestCase):
 
 
 class AccountDataTestCase(unittest.HomeserverTestCase):
-
     servlets = [
         synapse.rest.admin.register_servlets,
         login.register_servlets,
@@ -4325,7 +4346,6 @@ class AccountDataTestCase(unittest.HomeserverTestCase):
 
 
 class UsersByExternalIdTestCase(unittest.HomeserverTestCase):
-
     servlets = [
         synapse.rest.admin.register_servlets,
         login.register_servlets,
@@ -4409,3 +4429,97 @@ class UsersByExternalIdTestCase(unittest.HomeserverTestCase):
             {"user_id": self.other_user},
             channel.json_body,
         )
+
+
+class UsersByThreePidTestCase(unittest.HomeserverTestCase):
+    servlets = [
+        synapse.rest.admin.register_servlets,
+        login.register_servlets,
+    ]
+
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
+        self.store = hs.get_datastores().main
+
+        self.admin_user = self.register_user("admin", "pass", admin=True)
+        self.admin_user_tok = self.login("admin", "pass")
+
+        self.other_user = self.register_user("user", "pass")
+        self.get_success(
+            self.store.user_add_threepid(
+                self.other_user, "email", "user@email.com", 1, 1
+            )
+        )
+        self.get_success(
+            self.store.user_add_threepid(self.other_user, "msidn", "+1-12345678", 1, 1)
+        )
+
+    def test_no_auth(self) -> None:
+        """Try to look up a user without authentication."""
+        url = "/_synapse/admin/v1/threepid/email/users/user%40email.com"
+
+        channel = self.make_request(
+            "GET",
+            url,
+        )
+
+        self.assertEqual(401, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.MISSING_TOKEN, channel.json_body["errcode"])
+
+    def test_medium_does_not_exist(self) -> None:
+        """Tests that both a lookup for a medium that does not exist and a user that
+        doesn't exist with that third party ID returns a 404"""
+        # test for unknown medium
+        url = "/_synapse/admin/v1/threepid/publickey/users/unknown-key"
+
+        channel = self.make_request(
+            "GET",
+            url,
+            access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(404, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.NOT_FOUND, channel.json_body["errcode"])
+
+        # test for unknown user with a known medium
+        url = "/_synapse/admin/v1/threepid/email/users/unknown"
+
+        channel = self.make_request(
+            "GET",
+            url,
+            access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(404, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.NOT_FOUND, channel.json_body["errcode"])
+
+    def test_success(self) -> None:
+        """Tests a successful medium + address lookup"""
+        # test for email medium with encoded value of user@email.com
+        url = "/_synapse/admin/v1/threepid/email/users/user%40email.com"
+
+        channel = self.make_request(
+            "GET",
+            url,
+            access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertEqual(
+            {"user_id": self.other_user},
+            channel.json_body,
+        )
+
+        # test for msidn medium with encoded value of +1-12345678
+        url = "/_synapse/admin/v1/threepid/msidn/users/%2B1-12345678"
+
+        channel = self.make_request(
+            "GET",
+            url,
+            access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertEqual(
+            {"user_id": self.other_user},
+            channel.json_body,
+        )
diff --git a/tests/rest/client/test_auth.py b/tests/rest/client/test_auth.py
index 090cef5216..208ec44829 100644
--- a/tests/rest/client/test_auth.py
+++ b/tests/rest/client/test_auth.py
@@ -12,6 +12,7 @@
 # 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 re
 from http import HTTPStatus
 from typing import Any, Dict, List, Optional, Tuple, Union
 
@@ -21,7 +22,7 @@ from twisted.web.resource import Resource
 
 import synapse.rest.admin
 from synapse.api.constants import ApprovalNoticeMedium, LoginType
-from synapse.api.errors import Codes
+from synapse.api.errors import Codes, SynapseError
 from synapse.handlers.ui_auth.checkers import UserInteractiveAuthChecker
 from synapse.rest.client import account, auth, devices, login, logout, register
 from synapse.rest.synapse.client import build_synapse_client_resource_tree
@@ -32,8 +33,8 @@ from synapse.util import Clock
 
 from tests import unittest
 from tests.handlers.test_oidc import HAS_OIDC
-from tests.rest.client.utils import TEST_OIDC_CONFIG
-from tests.server import FakeChannel
+from tests.rest.client.utils import TEST_OIDC_CONFIG, TEST_OIDC_ISSUER
+from tests.server import FakeChannel, make_request
 from tests.unittest import override_config, skip_unless
 
 
@@ -465,9 +466,11 @@ class UIAuthTests(unittest.HomeserverTestCase):
           * checking that the original operation succeeds
         """
 
+        fake_oidc_server = self.helper.fake_oidc_server()
+
         # log the user in
         remote_user_id = UserID.from_string(self.user).localpart
-        login_resp = self.helper.login_via_oidc(remote_user_id)
+        login_resp, _ = self.helper.login_via_oidc(fake_oidc_server, remote_user_id)
         self.assertEqual(login_resp["user_id"], self.user)
 
         # initiate a UI Auth process by attempting to delete the device
@@ -481,8 +484,8 @@ class UIAuthTests(unittest.HomeserverTestCase):
 
         # run the UIA-via-SSO flow
         session_id = channel.json_body["session"]
-        channel = self.helper.auth_via_oidc(
-            {"sub": remote_user_id}, ui_auth_session_id=session_id
+        channel, _ = self.helper.auth_via_oidc(
+            fake_oidc_server, {"sub": remote_user_id}, ui_auth_session_id=session_id
         )
 
         # that should serve a confirmation page
@@ -499,7 +502,8 @@ class UIAuthTests(unittest.HomeserverTestCase):
     @skip_unless(HAS_OIDC, "requires OIDC")
     @override_config({"oidc_config": TEST_OIDC_CONFIG})
     def test_does_not_offer_password_for_sso_user(self) -> None:
-        login_resp = self.helper.login_via_oidc("username")
+        fake_oidc_server = self.helper.fake_oidc_server()
+        login_resp, _ = self.helper.login_via_oidc(fake_oidc_server, "username")
         user_tok = login_resp["access_token"]
         device_id = login_resp["device_id"]
 
@@ -522,7 +526,10 @@ class UIAuthTests(unittest.HomeserverTestCase):
     @override_config({"oidc_config": TEST_OIDC_CONFIG})
     def test_offers_both_flows_for_upgraded_user(self) -> None:
         """A user that had a password and then logged in with SSO should get both flows"""
-        login_resp = self.helper.login_via_oidc(UserID.from_string(self.user).localpart)
+        fake_oidc_server = self.helper.fake_oidc_server()
+        login_resp, _ = self.helper.login_via_oidc(
+            fake_oidc_server, UserID.from_string(self.user).localpart
+        )
         self.assertEqual(login_resp["user_id"], self.user)
 
         channel = self.delete_device(
@@ -539,8 +546,13 @@ class UIAuthTests(unittest.HomeserverTestCase):
     @override_config({"oidc_config": TEST_OIDC_CONFIG})
     def test_ui_auth_fails_for_incorrect_sso_user(self) -> None:
         """If the user tries to authenticate with the wrong SSO user, they get an error"""
+
+        fake_oidc_server = self.helper.fake_oidc_server()
+
         # log the user in
-        login_resp = self.helper.login_via_oidc(UserID.from_string(self.user).localpart)
+        login_resp, _ = self.helper.login_via_oidc(
+            fake_oidc_server, UserID.from_string(self.user).localpart
+        )
         self.assertEqual(login_resp["user_id"], self.user)
 
         # start a UI Auth flow by attempting to delete a device
@@ -553,8 +565,8 @@ class UIAuthTests(unittest.HomeserverTestCase):
         session_id = channel.json_body["session"]
 
         # do the OIDC auth, but auth as the wrong user
-        channel = self.helper.auth_via_oidc(
-            {"sub": "wrong_user"}, ui_auth_session_id=session_id
+        channel, _ = self.helper.auth_via_oidc(
+            fake_oidc_server, {"sub": "wrong_user"}, ui_auth_session_id=session_id
         )
 
         # that should return a failure message
@@ -584,7 +596,10 @@ class UIAuthTests(unittest.HomeserverTestCase):
         """Tests that if we register a user via SSO while requiring approval for new
         accounts, we still raise the correct error before logging the user in.
         """
-        login_resp = self.helper.login_via_oidc("username", expected_status=403)
+        fake_oidc_server = self.helper.fake_oidc_server()
+        login_resp, _ = self.helper.login_via_oidc(
+            fake_oidc_server, "username", expected_status=403
+        )
 
         self.assertEqual(login_resp["errcode"], Codes.USER_AWAITING_APPROVAL)
         self.assertEqual(
@@ -620,23 +635,10 @@ class RefreshAuthTests(unittest.HomeserverTestCase):
         """
         return self.make_request(
             "POST",
-            "/_matrix/client/v1/refresh",
+            "/_matrix/client/v3/refresh",
             {"refresh_token": refresh_token},
         )
 
-    def is_access_token_valid(self, access_token: str) -> bool:
-        """
-        Checks whether an access token is valid, returning whether it is or not.
-        """
-        code = self.make_request(
-            "GET", "/_matrix/client/v3/account/whoami", access_token=access_token
-        ).code
-
-        # Either 200 or 401 is what we get back; anything else is a bug.
-        assert code in {HTTPStatus.OK, HTTPStatus.UNAUTHORIZED}
-
-        return code == HTTPStatus.OK
-
     def test_login_issue_refresh_token(self) -> None:
         """
         A login response should include a refresh_token only if asked.
@@ -722,7 +724,7 @@ class RefreshAuthTests(unittest.HomeserverTestCase):
 
         refresh_response = self.make_request(
             "POST",
-            "/_matrix/client/v1/refresh",
+            "/_matrix/client/v3/refresh",
             {"refresh_token": login_response.json_body["refresh_token"]},
         )
         self.assertEqual(refresh_response.code, HTTPStatus.OK, refresh_response.result)
@@ -763,7 +765,7 @@ class RefreshAuthTests(unittest.HomeserverTestCase):
 
         refresh_response = self.make_request(
             "POST",
-            "/_matrix/client/v1/refresh",
+            "/_matrix/client/v3/refresh",
             {"refresh_token": login_response.json_body["refresh_token"]},
         )
         self.assertEqual(refresh_response.code, HTTPStatus.OK, refresh_response.result)
@@ -833,29 +835,37 @@ class RefreshAuthTests(unittest.HomeserverTestCase):
         self.reactor.advance(59.0)
 
         # Both tokens should still be valid.
-        self.assertTrue(self.is_access_token_valid(refreshable_access_token))
-        self.assertTrue(self.is_access_token_valid(nonrefreshable_access_token))
+        self.helper.whoami(refreshable_access_token, expect_code=HTTPStatus.OK)
+        self.helper.whoami(nonrefreshable_access_token, expect_code=HTTPStatus.OK)
 
         # Advance to 61 s (just past 1 minute, the time of expiry)
         self.reactor.advance(2.0)
 
         # Only the non-refreshable token is still valid.
-        self.assertFalse(self.is_access_token_valid(refreshable_access_token))
-        self.assertTrue(self.is_access_token_valid(nonrefreshable_access_token))
+        self.helper.whoami(
+            refreshable_access_token, expect_code=HTTPStatus.UNAUTHORIZED
+        )
+        self.helper.whoami(nonrefreshable_access_token, expect_code=HTTPStatus.OK)
 
         # Advance to 599 s (just shy of 10 minutes, the time of expiry)
         self.reactor.advance(599.0 - 61.0)
 
         # It's still the case that only the non-refreshable token is still valid.
-        self.assertFalse(self.is_access_token_valid(refreshable_access_token))
-        self.assertTrue(self.is_access_token_valid(nonrefreshable_access_token))
+        self.helper.whoami(
+            refreshable_access_token, expect_code=HTTPStatus.UNAUTHORIZED
+        )
+        self.helper.whoami(nonrefreshable_access_token, expect_code=HTTPStatus.OK)
 
         # Advance to 601 s (just past 10 minutes, the time of expiry)
         self.reactor.advance(2.0)
 
         # Now neither token is valid.
-        self.assertFalse(self.is_access_token_valid(refreshable_access_token))
-        self.assertFalse(self.is_access_token_valid(nonrefreshable_access_token))
+        self.helper.whoami(
+            refreshable_access_token, expect_code=HTTPStatus.UNAUTHORIZED
+        )
+        self.helper.whoami(
+            nonrefreshable_access_token, expect_code=HTTPStatus.UNAUTHORIZED
+        )
 
     @override_config(
         {"refreshable_access_token_lifetime": "1m", "refresh_token_lifetime": "2m"}
@@ -992,7 +1002,7 @@ class RefreshAuthTests(unittest.HomeserverTestCase):
         # This first refresh should work properly
         first_refresh_response = self.make_request(
             "POST",
-            "/_matrix/client/v1/refresh",
+            "/_matrix/client/v3/refresh",
             {"refresh_token": login_response.json_body["refresh_token"]},
         )
         self.assertEqual(
@@ -1002,7 +1012,7 @@ class RefreshAuthTests(unittest.HomeserverTestCase):
         # This one as well, since the token in the first one was never used
         second_refresh_response = self.make_request(
             "POST",
-            "/_matrix/client/v1/refresh",
+            "/_matrix/client/v3/refresh",
             {"refresh_token": login_response.json_body["refresh_token"]},
         )
         self.assertEqual(
@@ -1012,7 +1022,7 @@ class RefreshAuthTests(unittest.HomeserverTestCase):
         # This one should not, since the token from the first refresh is not valid anymore
         third_refresh_response = self.make_request(
             "POST",
-            "/_matrix/client/v1/refresh",
+            "/_matrix/client/v3/refresh",
             {"refresh_token": first_refresh_response.json_body["refresh_token"]},
         )
         self.assertEqual(
@@ -1046,7 +1056,7 @@ class RefreshAuthTests(unittest.HomeserverTestCase):
         # Now that the access token from the last valid refresh was used once, refreshing with the N-1 token should fail
         fourth_refresh_response = self.make_request(
             "POST",
-            "/_matrix/client/v1/refresh",
+            "/_matrix/client/v3/refresh",
             {"refresh_token": login_response.json_body["refresh_token"]},
         )
         self.assertEqual(
@@ -1058,7 +1068,7 @@ class RefreshAuthTests(unittest.HomeserverTestCase):
         # But refreshing from the last valid refresh token still works
         fifth_refresh_response = self.make_request(
             "POST",
-            "/_matrix/client/v1/refresh",
+            "/_matrix/client/v3/refresh",
             {"refresh_token": second_refresh_response.json_body["refresh_token"]},
         )
         self.assertEqual(
@@ -1151,3 +1161,349 @@ class RefreshAuthTests(unittest.HomeserverTestCase):
         # and no refresh token
         self.assertEqual(_table_length("access_tokens"), 0)
         self.assertEqual(_table_length("refresh_tokens"), 0)
+
+
+def oidc_config(
+    id: str, with_localpart_template: bool, **kwargs: Any
+) -> Dict[str, Any]:
+    """Sample OIDC provider config used in backchannel logout tests.
+
+    Args:
+        id: IDP ID for this provider
+        with_localpart_template: Set to `true` to have a default localpart_template in
+            the `user_mapping_provider` config and skip the user mapping session
+        **kwargs: rest of the config
+
+    Returns:
+        A dict suitable for the `oidc_config` or the `oidc_providers[]` parts of
+        the HS config
+    """
+    config: Dict[str, Any] = {
+        "idp_id": id,
+        "idp_name": id,
+        "issuer": TEST_OIDC_ISSUER,
+        "client_id": "test-client-id",
+        "client_secret": "test-client-secret",
+        "scopes": ["openid"],
+    }
+
+    if with_localpart_template:
+        config["user_mapping_provider"] = {
+            "config": {"localpart_template": "{{ user.sub }}"}
+        }
+    else:
+        config["user_mapping_provider"] = {"config": {}}
+
+    config.update(kwargs)
+
+    return config
+
+
+@skip_unless(HAS_OIDC, "Requires OIDC")
+class OidcBackchannelLogoutTests(unittest.HomeserverTestCase):
+    servlets = [
+        account.register_servlets,
+        login.register_servlets,
+    ]
+
+    def default_config(self) -> Dict[str, Any]:
+        config = super().default_config()
+
+        # public_baseurl uses an http:// scheme because FakeChannel.isSecure() returns
+        # False, so synapse will see the requested uri as http://..., so using http in
+        # the public_baseurl stops Synapse trying to redirect to https.
+        config["public_baseurl"] = "http://synapse.test"
+
+        return config
+
+    def create_resource_dict(self) -> Dict[str, Resource]:
+        resource_dict = super().create_resource_dict()
+        resource_dict.update(build_synapse_client_resource_tree(self.hs))
+        return resource_dict
+
+    def submit_logout_token(self, logout_token: str) -> FakeChannel:
+        return self.make_request(
+            "POST",
+            "/_synapse/client/oidc/backchannel_logout",
+            content=f"logout_token={logout_token}",
+            content_is_form=True,
+        )
+
+    @override_config(
+        {
+            "oidc_providers": [
+                oidc_config(
+                    id="oidc",
+                    with_localpart_template=True,
+                    backchannel_logout_enabled=True,
+                )
+            ]
+        }
+    )
+    def test_simple_logout(self) -> None:
+        """
+        Receiving a logout token should logout the user
+        """
+        fake_oidc_server = self.helper.fake_oidc_server()
+        user = "john"
+
+        login_resp, first_grant = self.helper.login_via_oidc(
+            fake_oidc_server, user, with_sid=True
+        )
+        first_access_token: str = login_resp["access_token"]
+        self.helper.whoami(first_access_token, expect_code=HTTPStatus.OK)
+
+        login_resp, second_grant = self.helper.login_via_oidc(
+            fake_oidc_server, user, with_sid=True
+        )
+        second_access_token: str = login_resp["access_token"]
+        self.helper.whoami(second_access_token, expect_code=HTTPStatus.OK)
+
+        self.assertNotEqual(first_grant.sid, second_grant.sid)
+        self.assertEqual(first_grant.userinfo["sub"], second_grant.userinfo["sub"])
+
+        # Logging out of the first session
+        logout_token = fake_oidc_server.generate_logout_token(first_grant)
+        channel = self.submit_logout_token(logout_token)
+        self.assertEqual(channel.code, 200)
+
+        self.helper.whoami(first_access_token, expect_code=HTTPStatus.UNAUTHORIZED)
+        self.helper.whoami(second_access_token, expect_code=HTTPStatus.OK)
+
+        # Logging out of the second session
+        logout_token = fake_oidc_server.generate_logout_token(second_grant)
+        channel = self.submit_logout_token(logout_token)
+        self.assertEqual(channel.code, 200)
+
+    @override_config(
+        {
+            "oidc_providers": [
+                oidc_config(
+                    id="oidc",
+                    with_localpart_template=True,
+                    backchannel_logout_enabled=True,
+                )
+            ]
+        }
+    )
+    def test_logout_during_login(self) -> None:
+        """
+        It should revoke login tokens when receiving a logout token
+        """
+        fake_oidc_server = self.helper.fake_oidc_server()
+        user = "john"
+
+        # Get an authentication, and logout before submitting the logout token
+        client_redirect_url = "https://x"
+        userinfo = {"sub": user}
+        channel, grant = self.helper.auth_via_oidc(
+            fake_oidc_server,
+            userinfo,
+            client_redirect_url,
+            with_sid=True,
+        )
+
+        # expect a confirmation page
+        self.assertEqual(channel.code, HTTPStatus.OK, channel.result)
+
+        # fish the matrix login token out of the body of the confirmation page
+        m = re.search(
+            'a href="%s.*loginToken=([^"]*)"' % (client_redirect_url,),
+            channel.text_body,
+        )
+        assert m, channel.text_body
+        login_token = m.group(1)
+
+        # Submit a logout
+        logout_token = fake_oidc_server.generate_logout_token(grant)
+        channel = self.submit_logout_token(logout_token)
+        self.assertEqual(channel.code, 200)
+
+        # Now try to exchange the login token
+        channel = make_request(
+            self.hs.get_reactor(),
+            self.site,
+            "POST",
+            "/login",
+            content={"type": "m.login.token", "token": login_token},
+        )
+        # It should have failed
+        self.assertEqual(channel.code, 403)
+
+    @override_config(
+        {
+            "oidc_providers": [
+                oidc_config(
+                    id="oidc",
+                    with_localpart_template=False,
+                    backchannel_logout_enabled=True,
+                )
+            ]
+        }
+    )
+    def test_logout_during_mapping(self) -> None:
+        """
+        It should stop ongoing user mapping session when receiving a logout token
+        """
+        fake_oidc_server = self.helper.fake_oidc_server()
+        user = "john"
+
+        # Get an authentication, and logout before submitting the logout token
+        client_redirect_url = "https://x"
+        userinfo = {"sub": user}
+        channel, grant = self.helper.auth_via_oidc(
+            fake_oidc_server,
+            userinfo,
+            client_redirect_url,
+            with_sid=True,
+        )
+
+        # Expect a user mapping page
+        self.assertEqual(channel.code, HTTPStatus.FOUND, channel.result)
+
+        # We should have a user_mapping_session cookie
+        cookie_headers = channel.headers.getRawHeaders("Set-Cookie")
+        assert cookie_headers
+        cookies: Dict[str, str] = {}
+        for h in cookie_headers:
+            key, value = h.split(";")[0].split("=", maxsplit=1)
+            cookies[key] = value
+
+        user_mapping_session_id = cookies["username_mapping_session"]
+
+        # Getting that session should not raise
+        session = self.hs.get_sso_handler().get_mapping_session(user_mapping_session_id)
+        self.assertIsNotNone(session)
+
+        # Submit a logout
+        logout_token = fake_oidc_server.generate_logout_token(grant)
+        channel = self.submit_logout_token(logout_token)
+        self.assertEqual(channel.code, 200)
+
+        # Now it should raise
+        with self.assertRaises(SynapseError):
+            self.hs.get_sso_handler().get_mapping_session(user_mapping_session_id)
+
+    @override_config(
+        {
+            "oidc_providers": [
+                oidc_config(
+                    id="oidc",
+                    with_localpart_template=True,
+                    backchannel_logout_enabled=False,
+                )
+            ]
+        }
+    )
+    def test_disabled(self) -> None:
+        """
+        Receiving a logout token should do nothing if it is disabled in the config
+        """
+        fake_oidc_server = self.helper.fake_oidc_server()
+        user = "john"
+
+        login_resp, grant = self.helper.login_via_oidc(
+            fake_oidc_server, user, with_sid=True
+        )
+        access_token: str = login_resp["access_token"]
+        self.helper.whoami(access_token, expect_code=HTTPStatus.OK)
+
+        # Logging out shouldn't work
+        logout_token = fake_oidc_server.generate_logout_token(grant)
+        channel = self.submit_logout_token(logout_token)
+        self.assertEqual(channel.code, 400)
+
+        # And the token should still be valid
+        self.helper.whoami(access_token, expect_code=HTTPStatus.OK)
+
+    @override_config(
+        {
+            "oidc_providers": [
+                oidc_config(
+                    id="oidc",
+                    with_localpart_template=True,
+                    backchannel_logout_enabled=True,
+                )
+            ]
+        }
+    )
+    def test_no_sid(self) -> None:
+        """
+        Receiving a logout token without `sid` during the login should do nothing
+        """
+        fake_oidc_server = self.helper.fake_oidc_server()
+        user = "john"
+
+        login_resp, grant = self.helper.login_via_oidc(
+            fake_oidc_server, user, with_sid=False
+        )
+        access_token: str = login_resp["access_token"]
+        self.helper.whoami(access_token, expect_code=HTTPStatus.OK)
+
+        # Logging out shouldn't work
+        logout_token = fake_oidc_server.generate_logout_token(grant)
+        channel = self.submit_logout_token(logout_token)
+        self.assertEqual(channel.code, 400)
+
+        # And the token should still be valid
+        self.helper.whoami(access_token, expect_code=HTTPStatus.OK)
+
+    @override_config(
+        {
+            "oidc_providers": [
+                oidc_config(
+                    "first",
+                    issuer="https://first-issuer.com/",
+                    with_localpart_template=True,
+                    backchannel_logout_enabled=True,
+                ),
+                oidc_config(
+                    "second",
+                    issuer="https://second-issuer.com/",
+                    with_localpart_template=True,
+                    backchannel_logout_enabled=True,
+                ),
+            ]
+        }
+    )
+    def test_multiple_providers(self) -> None:
+        """
+        It should be able to distinguish login tokens from two different IdPs
+        """
+        first_server = self.helper.fake_oidc_server(issuer="https://first-issuer.com/")
+        second_server = self.helper.fake_oidc_server(
+            issuer="https://second-issuer.com/"
+        )
+        user = "john"
+
+        login_resp, first_grant = self.helper.login_via_oidc(
+            first_server, user, with_sid=True, idp_id="oidc-first"
+        )
+        first_access_token: str = login_resp["access_token"]
+        self.helper.whoami(first_access_token, expect_code=HTTPStatus.OK)
+
+        login_resp, second_grant = self.helper.login_via_oidc(
+            second_server, user, with_sid=True, idp_id="oidc-second"
+        )
+        second_access_token: str = login_resp["access_token"]
+        self.helper.whoami(second_access_token, expect_code=HTTPStatus.OK)
+
+        # `sid` in the fake providers are generated by a counter, so the first grant of
+        # each provider should give the same SID
+        self.assertEqual(first_grant.sid, second_grant.sid)
+        self.assertEqual(first_grant.userinfo["sub"], second_grant.userinfo["sub"])
+
+        # Logging out of the first session
+        logout_token = first_server.generate_logout_token(first_grant)
+        channel = self.submit_logout_token(logout_token)
+        self.assertEqual(channel.code, 200)
+
+        self.helper.whoami(first_access_token, expect_code=HTTPStatus.UNAUTHORIZED)
+        self.helper.whoami(second_access_token, expect_code=HTTPStatus.OK)
+
+        # Logging out of the second session
+        logout_token = second_server.generate_logout_token(second_grant)
+        channel = self.submit_logout_token(logout_token)
+        self.assertEqual(channel.code, 200)
+
+        self.helper.whoami(second_access_token, expect_code=HTTPStatus.UNAUTHORIZED)
diff --git a/tests/rest/client/test_devices.py b/tests/rest/client/test_devices.py
index aa98222434..d80eea17d3 100644
--- a/tests/rest/client/test_devices.py
+++ b/tests/rest/client/test_devices.py
@@ -200,3 +200,37 @@ class DevicesTestCase(unittest.HomeserverTestCase):
         self.reactor.advance(43200)
         self.get_success(self.handler.get_device(user_id, "abc"))
         self.get_failure(self.handler.get_device(user_id, "def"), NotFoundError)
+
+
+class DehydratedDeviceTestCase(unittest.HomeserverTestCase):
+    servlets = [
+        admin.register_servlets_for_client_rest_resource,
+        login.register_servlets,
+        register.register_servlets,
+        devices.register_servlets,
+    ]
+
+    def test_PUT(self) -> None:
+        """Sanity-check that we can PUT a dehydrated device.
+
+        Detects https://github.com/matrix-org/synapse/issues/14334.
+        """
+        alice = self.register_user("alice", "correcthorse")
+        token = self.login(alice, "correcthorse")
+
+        # Have alice update their device list
+        channel = self.make_request(
+            "PUT",
+            "_matrix/client/unstable/org.matrix.msc2697.v2/dehydrated_device",
+            {
+                "device_data": {
+                    "algorithm": "org.matrix.msc2697.v1.dehydration.v1.olm",
+                    "account": "dehydrated_device",
+                }
+            },
+            access_token=token,
+            shorthand=False,
+        )
+        self.assertEqual(channel.code, HTTPStatus.OK, channel.json_body)
+        device_id = channel.json_body.get("device_id")
+        self.assertIsInstance(device_id, str)
diff --git a/tests/rest/client/test_login.py b/tests/rest/client/test_login.py
index e801ba8c8b..ff5baa9f0a 100644
--- a/tests/rest/client/test_login.py
+++ b/tests/rest/client/test_login.py
@@ -36,7 +36,7 @@ from synapse.util import Clock
 from tests import unittest
 from tests.handlers.test_oidc import HAS_OIDC
 from tests.handlers.test_saml import has_saml2
-from tests.rest.client.utils import TEST_OIDC_AUTH_ENDPOINT, TEST_OIDC_CONFIG
+from tests.rest.client.utils import TEST_OIDC_CONFIG
 from tests.server import FakeChannel
 from tests.test_utils.html_parsers import TestHtmlParser
 from tests.unittest import HomeserverTestCase, override_config, skip_unless
@@ -612,13 +612,16 @@ class MultiSSOTestCase(unittest.HomeserverTestCase):
     def test_login_via_oidc(self) -> None:
         """If OIDC is chosen, should redirect to the OIDC auth endpoint"""
 
-        # pick the default OIDC provider
-        channel = self.make_request(
-            "GET",
-            "/_synapse/client/pick_idp?redirectUrl="
-            + urllib.parse.quote_plus(TEST_CLIENT_REDIRECT_URL)
-            + "&idp=oidc",
-        )
+        fake_oidc_server = self.helper.fake_oidc_server()
+
+        with fake_oidc_server.patch_homeserver(hs=self.hs):
+            # pick the default OIDC provider
+            channel = self.make_request(
+                "GET",
+                "/_synapse/client/pick_idp?redirectUrl="
+                + urllib.parse.quote_plus(TEST_CLIENT_REDIRECT_URL)
+                + "&idp=oidc",
+            )
         self.assertEqual(channel.code, 302, channel.result)
         location_headers = channel.headers.getRawHeaders("Location")
         assert location_headers
@@ -626,7 +629,7 @@ class MultiSSOTestCase(unittest.HomeserverTestCase):
         oidc_uri_path, oidc_uri_query = oidc_uri.split("?", 1)
 
         # it should redirect us to the auth page of the OIDC server
-        self.assertEqual(oidc_uri_path, TEST_OIDC_AUTH_ENDPOINT)
+        self.assertEqual(oidc_uri_path, fake_oidc_server.authorization_endpoint)
 
         # ... and should have set a cookie including the redirect url
         cookie_headers = channel.headers.getRawHeaders("Set-Cookie")
@@ -643,7 +646,9 @@ class MultiSSOTestCase(unittest.HomeserverTestCase):
             TEST_CLIENT_REDIRECT_URL,
         )
 
-        channel = self.helper.complete_oidc_auth(oidc_uri, cookies, {"sub": "user1"})
+        channel, _ = self.helper.complete_oidc_auth(
+            fake_oidc_server, oidc_uri, cookies, {"sub": "user1"}
+        )
 
         # that should serve a confirmation page
         self.assertEqual(channel.code, 200, channel.result)
@@ -693,7 +698,10 @@ class MultiSSOTestCase(unittest.HomeserverTestCase):
 
     def test_client_idp_redirect_to_oidc(self) -> None:
         """If the client pick a known IdP, redirect to it"""
-        channel = self._make_sso_redirect_request("oidc")
+        fake_oidc_server = self.helper.fake_oidc_server()
+
+        with fake_oidc_server.patch_homeserver(hs=self.hs):
+            channel = self._make_sso_redirect_request("oidc")
         self.assertEqual(channel.code, 302, channel.result)
         location_headers = channel.headers.getRawHeaders("Location")
         assert location_headers
@@ -701,7 +709,7 @@ class MultiSSOTestCase(unittest.HomeserverTestCase):
         oidc_uri_path, oidc_uri_query = oidc_uri.split("?", 1)
 
         # it should redirect us to the auth page of the OIDC server
-        self.assertEqual(oidc_uri_path, TEST_OIDC_AUTH_ENDPOINT)
+        self.assertEqual(oidc_uri_path, fake_oidc_server.authorization_endpoint)
 
     def _make_sso_redirect_request(self, idp_prov: Optional[str] = None) -> FakeChannel:
         """Send a request to /_matrix/client/r0/login/sso/redirect
@@ -1280,9 +1288,13 @@ class UsernamePickerTestCase(HomeserverTestCase):
     def test_username_picker(self) -> None:
         """Test the happy path of a username picker flow."""
 
+        fake_oidc_server = self.helper.fake_oidc_server()
+
         # do the start of the login flow
-        channel = self.helper.auth_via_oidc(
-            {"sub": "tester", "displayname": "Jonny"}, TEST_CLIENT_REDIRECT_URL
+        channel, _ = self.helper.auth_via_oidc(
+            fake_oidc_server,
+            {"sub": "tester", "displayname": "Jonny"},
+            TEST_CLIENT_REDIRECT_URL,
         )
 
         # that should redirect to the username picker
diff --git a/tests/rest/client/test_login_token_request.py b/tests/rest/client/test_login_token_request.py
index c2e1e08811..6aedc1a11c 100644
--- a/tests/rest/client/test_login_token_request.py
+++ b/tests/rest/client/test_login_token_request.py
@@ -48,13 +48,13 @@ class LoginTokenRequestServletTestCase(unittest.HomeserverTestCase):
 
     def test_disabled(self) -> None:
         channel = self.make_request("POST", endpoint, {}, access_token=None)
-        self.assertEqual(channel.code, 400)
+        self.assertEqual(channel.code, 404)
 
         self.register_user(self.user, self.password)
         token = self.login(self.user, self.password)
 
         channel = self.make_request("POST", endpoint, {}, access_token=token)
-        self.assertEqual(channel.code, 400)
+        self.assertEqual(channel.code, 404)
 
     @override_config({"experimental_features": {"msc3882_enabled": True}})
     def test_require_auth(self) -> None:
diff --git a/tests/rest/client/test_receipts.py b/tests/rest/client/test_receipts.py
new file mode 100644
index 0000000000..2a7fcea386
--- /dev/null
+++ b/tests/rest/client/test_receipts.py
@@ -0,0 +1,76 @@
+# Copyright 2022 The Matrix.org Foundation C.I.C.
+#
+# 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.
+from twisted.test.proto_helpers import MemoryReactor
+
+import synapse.rest.admin
+from synapse.rest.client import login, receipts, register
+from synapse.server import HomeServer
+from synapse.util import Clock
+
+from tests import unittest
+
+
+class ReceiptsTestCase(unittest.HomeserverTestCase):
+    servlets = [
+        login.register_servlets,
+        register.register_servlets,
+        receipts.register_servlets,
+        synapse.rest.admin.register_servlets,
+    ]
+
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
+        self.owner = self.register_user("owner", "pass")
+        self.owner_tok = self.login("owner", "pass")
+
+    def test_send_receipt(self) -> None:
+        channel = self.make_request(
+            "POST",
+            "/rooms/!abc:beep/receipt/m.read/$def",
+            content={},
+            access_token=self.owner_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.result)
+
+    def test_send_receipt_invalid_room_id(self) -> None:
+        channel = self.make_request(
+            "POST",
+            "/rooms/not-a-room-id/receipt/m.read/$def",
+            content={},
+            access_token=self.owner_tok,
+        )
+        self.assertEqual(channel.code, 400, channel.result)
+        self.assertEqual(
+            channel.json_body["error"], "A valid room ID and event ID must be specified"
+        )
+
+    def test_send_receipt_invalid_event_id(self) -> None:
+        channel = self.make_request(
+            "POST",
+            "/rooms/!abc:beep/receipt/m.read/not-an-event-id",
+            content={},
+            access_token=self.owner_tok,
+        )
+        self.assertEqual(channel.code, 400, channel.result)
+        self.assertEqual(
+            channel.json_body["error"], "A valid room ID and event ID must be specified"
+        )
+
+    def test_send_receipt_invalid_receipt_type(self) -> None:
+        channel = self.make_request(
+            "POST",
+            "/rooms/!abc:beep/receipt/invalid-receipt-type/$def",
+            content={},
+            access_token=self.owner_tok,
+        )
+        self.assertEqual(channel.code, 400, channel.result)
diff --git a/tests/rest/client/test_redactions.py b/tests/rest/client/test_redactions.py
index be4c67d68e..5dfe44defb 100644
--- a/tests/rest/client/test_redactions.py
+++ b/tests/rest/client/test_redactions.py
@@ -11,17 +11,18 @@
 # 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.
-from typing import List
+from typing import List, Optional
 
 from twisted.test.proto_helpers import MemoryReactor
 
+from synapse.api.constants import EventTypes, RelationTypes
 from synapse.rest import admin
 from synapse.rest.client import login, room, sync
 from synapse.server import HomeServer
 from synapse.types import JsonDict
 from synapse.util import Clock
 
-from tests.unittest import HomeserverTestCase
+from tests.unittest import HomeserverTestCase, override_config
 
 
 class RedactionsTestCase(HomeserverTestCase):
@@ -67,7 +68,12 @@ class RedactionsTestCase(HomeserverTestCase):
         )
 
     def _redact_event(
-        self, access_token: str, room_id: str, event_id: str, expect_code: int = 200
+        self,
+        access_token: str,
+        room_id: str,
+        event_id: str,
+        expect_code: int = 200,
+        with_relations: Optional[List[str]] = None,
     ) -> JsonDict:
         """Helper function to send a redaction event.
 
@@ -75,7 +81,13 @@ class RedactionsTestCase(HomeserverTestCase):
         """
         path = "/_matrix/client/r0/rooms/%s/redact/%s" % (room_id, event_id)
 
-        channel = self.make_request("POST", path, content={}, access_token=access_token)
+        request_content = {}
+        if with_relations:
+            request_content["org.matrix.msc3912.with_relations"] = with_relations
+
+        channel = self.make_request(
+            "POST", path, request_content, access_token=access_token
+        )
         self.assertEqual(channel.code, expect_code)
         return channel.json_body
 
@@ -201,3 +213,256 @@ class RedactionsTestCase(HomeserverTestCase):
             # These should all succeed, even though this would be denied by
             # the standard message ratelimiter
             self._redact_event(self.mod_access_token, self.room_id, msg_id)
+
+    @override_config({"experimental_features": {"msc3912_enabled": True}})
+    def test_redact_relations(self) -> None:
+        """Tests that we can redact the relations of an event at the same time as the
+        event itself.
+        """
+        # Send a root event.
+        res = self.helper.send_event(
+            room_id=self.room_id,
+            type=EventTypes.Message,
+            content={"msgtype": "m.text", "body": "hello"},
+            tok=self.mod_access_token,
+        )
+        root_event_id = res["event_id"]
+
+        # Send an edit to this root event.
+        res = self.helper.send_event(
+            room_id=self.room_id,
+            type=EventTypes.Message,
+            content={
+                "body": " * hello world",
+                "m.new_content": {
+                    "body": "hello world",
+                    "msgtype": "m.text",
+                },
+                "m.relates_to": {
+                    "event_id": root_event_id,
+                    "rel_type": RelationTypes.REPLACE,
+                },
+                "msgtype": "m.text",
+            },
+            tok=self.mod_access_token,
+        )
+        edit_event_id = res["event_id"]
+
+        # Also send a threaded message whose root is the same as the edit's.
+        res = self.helper.send_event(
+            room_id=self.room_id,
+            type=EventTypes.Message,
+            content={
+                "msgtype": "m.text",
+                "body": "message 1",
+                "m.relates_to": {
+                    "event_id": root_event_id,
+                    "rel_type": RelationTypes.THREAD,
+                },
+            },
+            tok=self.mod_access_token,
+        )
+        threaded_event_id = res["event_id"]
+
+        # Also send a reaction, again with the same root.
+        res = self.helper.send_event(
+            room_id=self.room_id,
+            type=EventTypes.Reaction,
+            content={
+                "m.relates_to": {
+                    "rel_type": RelationTypes.ANNOTATION,
+                    "event_id": root_event_id,
+                    "key": "👍",
+                }
+            },
+            tok=self.mod_access_token,
+        )
+        reaction_event_id = res["event_id"]
+
+        # Redact the root event, specifying that we also want to delete events that
+        # relate to it with m.replace.
+        self._redact_event(
+            self.mod_access_token,
+            self.room_id,
+            root_event_id,
+            with_relations=[
+                RelationTypes.REPLACE,
+                RelationTypes.THREAD,
+            ],
+        )
+
+        # Check that the root event got redacted.
+        event_dict = self.helper.get_event(
+            self.room_id, root_event_id, self.mod_access_token
+        )
+        self.assertIn("redacted_because", event_dict, event_dict)
+
+        # Check that the edit got redacted.
+        event_dict = self.helper.get_event(
+            self.room_id, edit_event_id, self.mod_access_token
+        )
+        self.assertIn("redacted_because", event_dict, event_dict)
+
+        # Check that the threaded message got redacted.
+        event_dict = self.helper.get_event(
+            self.room_id, threaded_event_id, self.mod_access_token
+        )
+        self.assertIn("redacted_because", event_dict, event_dict)
+
+        # Check that the reaction did not get redacted.
+        event_dict = self.helper.get_event(
+            self.room_id, reaction_event_id, self.mod_access_token
+        )
+        self.assertNotIn("redacted_because", event_dict, event_dict)
+
+    @override_config({"experimental_features": {"msc3912_enabled": True}})
+    def test_redact_relations_no_perms(self) -> None:
+        """Tests that, when redacting a message along with its relations, if not all
+        the related messages can be redacted because of insufficient permissions, the
+        server still redacts all the ones that can be.
+        """
+        # Send a root event.
+        res = self.helper.send_event(
+            room_id=self.room_id,
+            type=EventTypes.Message,
+            content={
+                "msgtype": "m.text",
+                "body": "root",
+            },
+            tok=self.other_access_token,
+        )
+        root_event_id = res["event_id"]
+
+        # Send a first threaded message, this one from the moderator. We do this for the
+        # first message with the m.thread relation (and not the last one) to ensure
+        # that, when the server fails to redact it, it doesn't stop there, and it
+        # instead goes on to redact the other one.
+        res = self.helper.send_event(
+            room_id=self.room_id,
+            type=EventTypes.Message,
+            content={
+                "msgtype": "m.text",
+                "body": "message 1",
+                "m.relates_to": {
+                    "event_id": root_event_id,
+                    "rel_type": RelationTypes.THREAD,
+                },
+            },
+            tok=self.mod_access_token,
+        )
+        first_threaded_event_id = res["event_id"]
+
+        # Send a second threaded message, this time from the user who'll perform the
+        # redaction.
+        res = self.helper.send_event(
+            room_id=self.room_id,
+            type=EventTypes.Message,
+            content={
+                "msgtype": "m.text",
+                "body": "message 2",
+                "m.relates_to": {
+                    "event_id": root_event_id,
+                    "rel_type": RelationTypes.THREAD,
+                },
+            },
+            tok=self.other_access_token,
+        )
+        second_threaded_event_id = res["event_id"]
+
+        # Redact the thread's root, and request that all threaded messages are also
+        # redacted. Send that request from the non-mod user, so that the first threaded
+        # event cannot be redacted.
+        self._redact_event(
+            self.other_access_token,
+            self.room_id,
+            root_event_id,
+            with_relations=[RelationTypes.THREAD],
+        )
+
+        # Check that the thread root got redacted.
+        event_dict = self.helper.get_event(
+            self.room_id, root_event_id, self.other_access_token
+        )
+        self.assertIn("redacted_because", event_dict, event_dict)
+
+        # Check that the last message in the thread got redacted, despite failing to
+        # redact the one before it.
+        event_dict = self.helper.get_event(
+            self.room_id, second_threaded_event_id, self.other_access_token
+        )
+        self.assertIn("redacted_because", event_dict, event_dict)
+
+        # Check that the message that was sent into the tread by the mod user is not
+        # redacted.
+        event_dict = self.helper.get_event(
+            self.room_id, first_threaded_event_id, self.other_access_token
+        )
+        self.assertIn("body", event_dict["content"], event_dict)
+        self.assertEqual("message 1", event_dict["content"]["body"])
+
+    @override_config({"experimental_features": {"msc3912_enabled": True}})
+    def test_redact_relations_txn_id_reuse(self) -> None:
+        """Tests that redacting a message using a transaction ID, then reusing the same
+        transaction ID but providing an additional list of relations to redact, is
+        effectively a no-op.
+        """
+        # Send a root event.
+        res = self.helper.send_event(
+            room_id=self.room_id,
+            type=EventTypes.Message,
+            content={
+                "msgtype": "m.text",
+                "body": "root",
+            },
+            tok=self.mod_access_token,
+        )
+        root_event_id = res["event_id"]
+
+        # Send a first threaded message.
+        res = self.helper.send_event(
+            room_id=self.room_id,
+            type=EventTypes.Message,
+            content={
+                "msgtype": "m.text",
+                "body": "I'm in a thread!",
+                "m.relates_to": {
+                    "event_id": root_event_id,
+                    "rel_type": RelationTypes.THREAD,
+                },
+            },
+            tok=self.mod_access_token,
+        )
+        threaded_event_id = res["event_id"]
+
+        # Send a first redaction request which redacts only the root event.
+        channel = self.make_request(
+            method="PUT",
+            path=f"/rooms/{self.room_id}/redact/{root_event_id}/foo",
+            content={},
+            access_token=self.mod_access_token,
+        )
+        self.assertEqual(channel.code, 200)
+
+        # Send a second redaction request which redacts the root event as well as
+        # threaded messages.
+        channel = self.make_request(
+            method="PUT",
+            path=f"/rooms/{self.room_id}/redact/{root_event_id}/foo",
+            content={"org.matrix.msc3912.with_relations": [RelationTypes.THREAD]},
+            access_token=self.mod_access_token,
+        )
+        self.assertEqual(channel.code, 200)
+
+        # Check that the root event got redacted.
+        event_dict = self.helper.get_event(
+            self.room_id, root_event_id, self.mod_access_token
+        )
+        self.assertIn("redacted_because", event_dict)
+
+        # Check that the threaded message didn't get redacted (since that wasn't part of
+        # the original redaction).
+        event_dict = self.helper.get_event(
+            self.room_id, threaded_event_id, self.mod_access_token
+        )
+        self.assertIn("body", event_dict["content"], event_dict)
+        self.assertEqual("I'm in a thread!", event_dict["content"]["body"])
diff --git a/tests/rest/client/test_relations.py b/tests/rest/client/test_relations.py
index 988cdb746d..b86f341ff5 100644
--- a/tests/rest/client/test_relations.py
+++ b/tests/rest/client/test_relations.py
@@ -1108,7 +1108,7 @@ class BundledAggregationsTestCase(BaseRelationsTestCase):
 
         # The "user" sent the root event and is making queries for the bundled
         # aggregations: they have participated.
-        self._test_bundled_aggregations(RelationTypes.THREAD, _gen_assert(True), 9)
+        self._test_bundled_aggregations(RelationTypes.THREAD, _gen_assert(True), 7)
         # The "user2" sent replies in the thread and is making queries for the
         # bundled aggregations: they have participated.
         #
@@ -1170,7 +1170,7 @@ class BundledAggregationsTestCase(BaseRelationsTestCase):
                 bundled_aggregations["latest_event"].get("unsigned"),
             )
 
-        self._test_bundled_aggregations(RelationTypes.THREAD, assert_thread, 9)
+        self._test_bundled_aggregations(RelationTypes.THREAD, assert_thread, 7)
 
     def test_nested_thread(self) -> None:
         """
@@ -1523,6 +1523,26 @@ class RelationRedactionTestCase(BaseRelationsTestCase):
         )
         self.assertEqual(200, channel.code, channel.json_body)
 
+    def _get_threads(self) -> List[Tuple[str, str]]:
+        """Request the threads in the room and returns a list of thread ID and latest event ID."""
+        # Request the threads in the room.
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/threads",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        threads = channel.json_body["chunk"]
+        return [
+            (
+                t["event_id"],
+                t["unsigned"]["m.relations"][RelationTypes.THREAD]["latest_event"][
+                    "event_id"
+                ],
+            )
+            for t in threads
+        ]
+
     def test_redact_relation_annotation(self) -> None:
         """
         Test that annotations of an event are properly handled after the
@@ -1567,58 +1587,82 @@ class RelationRedactionTestCase(BaseRelationsTestCase):
         The redacted event should not be included in bundled aggregations or
         the response to relations.
         """
-        channel = self._send_relation(
-            RelationTypes.THREAD,
-            EventTypes.Message,
-            content={"body": "reply 1", "msgtype": "m.text"},
-        )
-        unredacted_event_id = channel.json_body["event_id"]
+        # Create a thread with a few events in it.
+        thread_replies = []
+        for i in range(3):
+            channel = self._send_relation(
+                RelationTypes.THREAD,
+                EventTypes.Message,
+                content={"body": f"reply {i}", "msgtype": "m.text"},
+            )
+            thread_replies.append(channel.json_body["event_id"])
 
-        # Note that the *last* event in the thread is redacted, as that gets
-        # included in the bundled aggregation.
-        channel = self._send_relation(
-            RelationTypes.THREAD,
-            EventTypes.Message,
-            content={"body": "reply 2", "msgtype": "m.text"},
+        ##################################################
+        # Check the test data is configured as expected. #
+        ##################################################
+        self.assertEquals(self._get_related_events(), list(reversed(thread_replies)))
+        relations = self._get_bundled_aggregations()
+        self.assertDictContainsSubset(
+            {"count": 3, "current_user_participated": True},
+            relations[RelationTypes.THREAD],
+        )
+        # The latest event is the last sent event.
+        self.assertEqual(
+            relations[RelationTypes.THREAD]["latest_event"]["event_id"],
+            thread_replies[-1],
         )
-        to_redact_event_id = channel.json_body["event_id"]
 
-        # Both relations exist.
-        event_ids = self._get_related_events()
+        # There should be one thread, the latest event is the event that will be redacted.
+        self.assertEqual(self._get_threads(), [(self.parent_id, thread_replies[-1])])
+
+        ##########################
+        # Redact the last event. #
+        ##########################
+        self._redact(thread_replies.pop())
+
+        # The thread should still exist, but the latest event should be updated.
+        self.assertEquals(self._get_related_events(), list(reversed(thread_replies)))
         relations = self._get_bundled_aggregations()
-        self.assertEquals(event_ids, [to_redact_event_id, unredacted_event_id])
         self.assertDictContainsSubset(
-            {
-                "count": 2,
-                "current_user_participated": True,
-            },
+            {"count": 2, "current_user_participated": True},
             relations[RelationTypes.THREAD],
         )
-        # And the latest event returned is the event that will be redacted.
+        # And the latest event is the last unredacted event.
         self.assertEqual(
             relations[RelationTypes.THREAD]["latest_event"]["event_id"],
-            to_redact_event_id,
+            thread_replies[-1],
         )
+        self.assertEqual(self._get_threads(), [(self.parent_id, thread_replies[-1])])
 
-        # Redact one of the reactions.
-        self._redact(to_redact_event_id)
+        ###########################################
+        # Redact the *first* event in the thread. #
+        ###########################################
+        self._redact(thread_replies.pop(0))
 
-        # The unredacted relation should still exist.
-        event_ids = self._get_related_events()
+        # Nothing should have changed (except the thread count).
+        self.assertEquals(self._get_related_events(), thread_replies)
         relations = self._get_bundled_aggregations()
-        self.assertEquals(event_ids, [unredacted_event_id])
         self.assertDictContainsSubset(
-            {
-                "count": 1,
-                "current_user_participated": True,
-            },
+            {"count": 1, "current_user_participated": True},
             relations[RelationTypes.THREAD],
         )
-        # And the latest event is now the unredacted event.
+        # And the latest event is the last unredacted event.
         self.assertEqual(
             relations[RelationTypes.THREAD]["latest_event"]["event_id"],
-            unredacted_event_id,
+            thread_replies[-1],
         )
+        self.assertEqual(self._get_threads(), [(self.parent_id, thread_replies[-1])])
+
+        ####################################
+        # Redact the last remaining event. #
+        ####################################
+        self._redact(thread_replies.pop(0))
+        self.assertEquals(thread_replies, [])
+
+        # The event should no longer be considered a thread.
+        self.assertEquals(self._get_related_events(), [])
+        self.assertEquals(self._get_bundled_aggregations(), {})
+        self.assertEqual(self._get_threads(), [])
 
     def test_redact_parent_edit(self) -> None:
         """Test that edits of an event are redacted when the original event
@@ -1677,7 +1721,6 @@ class RelationRedactionTestCase(BaseRelationsTestCase):
             {"chunk": [{"type": "m.reaction", "key": "👍", "count": 1}]},
         )
 
-    @unittest.override_config({"experimental_features": {"msc3440_enabled": True}})
     def test_redact_parent_thread(self) -> None:
         """
         Test that thread replies are still available when the root event is redacted.
@@ -1707,3 +1750,165 @@ class RelationRedactionTestCase(BaseRelationsTestCase):
             relations[RelationTypes.THREAD]["latest_event"]["event_id"],
             related_event_id,
         )
+
+
+class ThreadsTestCase(BaseRelationsTestCase):
+    def _get_threads(self, body: JsonDict) -> List[Tuple[str, str]]:
+        return [
+            (
+                ev["event_id"],
+                ev["unsigned"]["m.relations"]["m.thread"]["latest_event"]["event_id"],
+            )
+            for ev in body["chunk"]
+        ]
+
+    def test_threads(self) -> None:
+        """Create threads and ensure the ordering is due to their latest event."""
+        # Create 2 threads.
+        thread_1 = self.parent_id
+        res = self.helper.send(self.room, body="Thread Root!", tok=self.user_token)
+        thread_2 = res["event_id"]
+
+        channel = self._send_relation(RelationTypes.THREAD, "m.room.test")
+        reply_1 = channel.json_body["event_id"]
+        channel = self._send_relation(
+            RelationTypes.THREAD, "m.room.test", parent_id=thread_2
+        )
+        reply_2 = channel.json_body["event_id"]
+
+        # Request the threads in the room.
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/threads",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        threads = self._get_threads(channel.json_body)
+        self.assertEqual(threads, [(thread_2, reply_2), (thread_1, reply_1)])
+
+        # Update the first thread, the ordering should swap.
+        channel = self._send_relation(RelationTypes.THREAD, "m.room.test")
+        reply_3 = channel.json_body["event_id"]
+
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/threads",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        # Tuple of (thread ID, latest event ID) for each thread.
+        threads = self._get_threads(channel.json_body)
+        self.assertEqual(threads, [(thread_1, reply_3), (thread_2, reply_2)])
+
+    def test_pagination(self) -> None:
+        """Create threads and paginate through them."""
+        # Create 2 threads.
+        thread_1 = self.parent_id
+        res = self.helper.send(self.room, body="Thread Root!", tok=self.user_token)
+        thread_2 = res["event_id"]
+
+        self._send_relation(RelationTypes.THREAD, "m.room.test")
+        self._send_relation(RelationTypes.THREAD, "m.room.test", parent_id=thread_2)
+
+        # Request the threads in the room.
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/threads?limit=1",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        thread_roots = [ev["event_id"] for ev in channel.json_body["chunk"]]
+        self.assertEqual(thread_roots, [thread_2])
+
+        # Make sure next_batch has something in it that looks like it could be a
+        # valid token.
+        next_batch = channel.json_body.get("next_batch")
+        self.assertIsInstance(next_batch, str, channel.json_body)
+
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/threads?limit=1&from={next_batch}",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        thread_roots = [ev["event_id"] for ev in channel.json_body["chunk"]]
+        self.assertEqual(thread_roots, [thread_1], channel.json_body)
+
+        self.assertNotIn("next_batch", channel.json_body, channel.json_body)
+
+    def test_include(self) -> None:
+        """Filtering threads to all or participated in should work."""
+        # Thread 1 has the user as the root event.
+        thread_1 = self.parent_id
+        self._send_relation(
+            RelationTypes.THREAD, "m.room.test", access_token=self.user2_token
+        )
+
+        # Thread 2 has the user replying.
+        res = self.helper.send(self.room, body="Thread Root!", tok=self.user2_token)
+        thread_2 = res["event_id"]
+        self._send_relation(RelationTypes.THREAD, "m.room.test", parent_id=thread_2)
+
+        # Thread 3 has the user not participating in.
+        res = self.helper.send(self.room, body="Another thread!", tok=self.user2_token)
+        thread_3 = res["event_id"]
+        self._send_relation(
+            RelationTypes.THREAD,
+            "m.room.test",
+            access_token=self.user2_token,
+            parent_id=thread_3,
+        )
+
+        # All threads in the room.
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/threads",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        thread_roots = [ev["event_id"] for ev in channel.json_body["chunk"]]
+        self.assertEqual(
+            thread_roots, [thread_3, thread_2, thread_1], channel.json_body
+        )
+
+        # Only participated threads.
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/threads?include=participated",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        thread_roots = [ev["event_id"] for ev in channel.json_body["chunk"]]
+        self.assertEqual(thread_roots, [thread_2, thread_1], channel.json_body)
+
+    def test_ignored_user(self) -> None:
+        """Events from ignored users should be ignored."""
+        # Thread 1 has a reply from an ignored user.
+        thread_1 = self.parent_id
+        self._send_relation(
+            RelationTypes.THREAD, "m.room.test", access_token=self.user2_token
+        )
+
+        # Thread 2 is created by an ignored user.
+        res = self.helper.send(self.room, body="Thread Root!", tok=self.user2_token)
+        thread_2 = res["event_id"]
+        self._send_relation(RelationTypes.THREAD, "m.room.test", parent_id=thread_2)
+
+        # Ignore user2.
+        self.get_success(
+            self.store.add_account_data_for_user(
+                self.user_id,
+                AccountDataTypes.IGNORED_USER_LIST,
+                {"ignored_users": {self.user2_id: {}}},
+            )
+        )
+
+        # Only thread 1 is returned.
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/threads",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        thread_roots = [ev["event_id"] for ev in channel.json_body["chunk"]]
+        self.assertEqual(thread_roots, [thread_1], channel.json_body)
diff --git a/tests/rest/client/test_rendezvous.py b/tests/rest/client/test_rendezvous.py
new file mode 100644
index 0000000000..c0eb5d01a6
--- /dev/null
+++ b/tests/rest/client/test_rendezvous.py
@@ -0,0 +1,45 @@
+# Copyright 2022 The Matrix.org Foundation C.I.C.
+#
+# 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.
+
+from twisted.test.proto_helpers import MemoryReactor
+
+from synapse.rest.client import rendezvous
+from synapse.server import HomeServer
+from synapse.util import Clock
+
+from tests import unittest
+from tests.unittest import override_config
+
+endpoint = "/_matrix/client/unstable/org.matrix.msc3886/rendezvous"
+
+
+class RendezvousServletTestCase(unittest.HomeserverTestCase):
+
+    servlets = [
+        rendezvous.register_servlets,
+    ]
+
+    def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
+        self.hs = self.setup_test_homeserver()
+        return self.hs
+
+    def test_disabled(self) -> None:
+        channel = self.make_request("POST", endpoint, {}, access_token=None)
+        self.assertEqual(channel.code, 404)
+
+    @override_config({"experimental_features": {"msc3886_endpoint": "/asd"}})
+    def test_redirect(self) -> None:
+        channel = self.make_request("POST", endpoint, {}, access_token=None)
+        self.assertEqual(channel.code, 307)
+        self.assertEqual(channel.headers.getRawHeaders("Location"), ["/asd"])
diff --git a/tests/rest/client/test_rooms.py b/tests/rest/client/test_rooms.py
index 3612ebe7b9..b4daace556 100644
--- a/tests/rest/client/test_rooms.py
+++ b/tests/rest/client/test_rooms.py
@@ -35,11 +35,12 @@ from synapse.api.constants import (
     EventTypes,
     Membership,
     PublicRoomsFilterFields,
-    RelationTypes,
     RoomTypes,
 )
 from synapse.api.errors import Codes, HttpResponseException
 from synapse.appservice import ApplicationService
+from synapse.events import EventBase
+from synapse.events.snapshot import EventContext
 from synapse.handlers.pagination import PurgeStatus
 from synapse.rest import admin
 from synapse.rest.client import account, directory, login, profile, register, room, sync
@@ -50,7 +51,10 @@ from synapse.util.stringutils import random_string
 
 from tests import unittest
 from tests.http.server._base import make_request_with_cancellation_test
+from tests.storage.test_stream import PaginationTestCase
 from tests.test_utils import make_awaitable
+from tests.test_utils.event_injection import create_event
+from tests.unittest import override_config
 
 PATH_PREFIX = b"/_matrix/client/api/v1"
 
@@ -711,7 +715,7 @@ class RoomsCreateTestCase(RoomBase):
         self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
         self.assertTrue("room_id" in channel.json_body)
         assert channel.resource_usage is not None
-        self.assertEqual(34, channel.resource_usage.db_txn_count)
+        self.assertEqual(33, channel.resource_usage.db_txn_count)
 
     def test_post_room_initial_state(self) -> None:
         # POST with initial_state config key, expect new room id
@@ -724,7 +728,7 @@ class RoomsCreateTestCase(RoomBase):
         self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
         self.assertTrue("room_id" in channel.json_body)
         assert channel.resource_usage is not None
-        self.assertEqual(37, channel.resource_usage.db_txn_count)
+        self.assertEqual(36, channel.resource_usage.db_txn_count)
 
     def test_post_room_visibility_key(self) -> None:
         # POST with visibility config key, expect new room id
@@ -868,6 +872,41 @@ class RoomsCreateTestCase(RoomBase):
         self.assertEqual(channel.code, HTTPStatus.OK, channel.json_body)
         self.assertEqual(join_mock.call_count, 0)
 
+    def _create_basic_room(self) -> Tuple[int, object]:
+        """
+        Tries to create a basic room and returns the response code.
+        """
+        channel = self.make_request(
+            "POST",
+            "/createRoom",
+            {},
+        )
+        return channel.code, channel.json_body
+
+    @override_config(
+        {
+            "rc_message": {"per_second": 0.2, "burst_count": 10},
+        }
+    )
+    def test_room_creation_ratelimiting(self) -> None:
+        """
+        Regression test for #14312, where ratelimiting was made too strict.
+        Clients should be able to create 10 rooms in a row
+        without hitting rate limits, using default rate limit config.
+        (We override rate limiting config back to its default value.)
+
+        To ensure we don't make ratelimiting too generous accidentally,
+        also check that we can't create an 11th room.
+        """
+
+        for _ in range(10):
+            code, json_body = self._create_basic_room()
+            self.assertEqual(code, HTTPStatus.OK, json_body)
+
+        # The 6th room hits the rate limit.
+        code, json_body = self._create_basic_room()
+        self.assertEqual(code, HTTPStatus.TOO_MANY_REQUESTS, json_body)
+
 
 class RoomTopicTestCase(RoomBase):
     """Tests /rooms/$room_id/topic REST events."""
@@ -1387,10 +1426,22 @@ class RoomJoinRatelimitTestCase(RoomBase):
     )
     def test_join_local_ratelimit(self) -> None:
         """Tests that local joins are actually rate-limited."""
-        for _ in range(3):
-            self.helper.create_room_as(self.user_id)
+        # Create 4 rooms
+        room_ids = [
+            self.helper.create_room_as(self.user_id, is_public=True) for _ in range(4)
+        ]
+
+        joiner_user_id = self.register_user("joiner", "secret")
+        # Now make a new user try to join some of them.
 
-        self.helper.create_room_as(self.user_id, expect_code=429)
+        # The user can join 3 rooms
+        for room_id in room_ids[0:3]:
+            self.helper.join(room_id, joiner_user_id)
+
+        # But the user cannot join a 4th room
+        self.helper.join(
+            room_ids[3], joiner_user_id, expect_code=HTTPStatus.TOO_MANY_REQUESTS
+        )
 
     @unittest.override_config(
         {"rc_joins": {"local": {"per_second": 0.5, "burst_count": 3}}}
@@ -2915,149 +2966,20 @@ class LabelsTestCase(unittest.HomeserverTestCase):
         return event_id
 
 
-class RelationsTestCase(unittest.HomeserverTestCase):
-    servlets = [
-        synapse.rest.admin.register_servlets_for_client_rest_resource,
-        room.register_servlets,
-        login.register_servlets,
-    ]
-
-    def default_config(self) -> Dict[str, Any]:
-        config = super().default_config()
-        config["experimental_features"] = {"msc3440_enabled": True}
-        return config
-
-    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
-        self.user_id = self.register_user("test", "test")
-        self.tok = self.login("test", "test")
-        self.room_id = self.helper.create_room_as(self.user_id, tok=self.tok)
-
-        self.second_user_id = self.register_user("second", "test")
-        self.second_tok = self.login("second", "test")
-        self.helper.join(
-            room=self.room_id, user=self.second_user_id, tok=self.second_tok
-        )
-
-        self.third_user_id = self.register_user("third", "test")
-        self.third_tok = self.login("third", "test")
-        self.helper.join(room=self.room_id, user=self.third_user_id, tok=self.third_tok)
-
-        # An initial event with a relation from second user.
-        res = self.helper.send_event(
-            room_id=self.room_id,
-            type=EventTypes.Message,
-            content={"msgtype": "m.text", "body": "Message 1"},
-            tok=self.tok,
-        )
-        self.event_id_1 = res["event_id"]
-        self.helper.send_event(
-            room_id=self.room_id,
-            type="m.reaction",
-            content={
-                "m.relates_to": {
-                    "rel_type": RelationTypes.ANNOTATION,
-                    "event_id": self.event_id_1,
-                    "key": "👍",
-                }
-            },
-            tok=self.second_tok,
-        )
-
-        # Another event with a relation from third user.
-        res = self.helper.send_event(
-            room_id=self.room_id,
-            type=EventTypes.Message,
-            content={"msgtype": "m.text", "body": "Message 2"},
-            tok=self.tok,
-        )
-        self.event_id_2 = res["event_id"]
-        self.helper.send_event(
-            room_id=self.room_id,
-            type="m.reaction",
-            content={
-                "m.relates_to": {
-                    "rel_type": RelationTypes.REFERENCE,
-                    "event_id": self.event_id_2,
-                }
-            },
-            tok=self.third_tok,
-        )
-
-        # An event with no relations.
-        self.helper.send_event(
-            room_id=self.room_id,
-            type=EventTypes.Message,
-            content={"msgtype": "m.text", "body": "No relations"},
-            tok=self.tok,
-        )
-
-    def _filter_messages(self, filter: JsonDict) -> List[JsonDict]:
+class RelationsTestCase(PaginationTestCase):
+    def _filter_messages(self, filter: JsonDict) -> List[str]:
         """Make a request to /messages with a filter, returns the chunk of events."""
+        from_token = self.get_success(
+            self.from_token.to_string(self.hs.get_datastores().main)
+        )
         channel = self.make_request(
             "GET",
-            "/rooms/%s/messages?filter=%s&dir=b" % (self.room_id, json.dumps(filter)),
+            f"/rooms/{self.room_id}/messages?filter={json.dumps(filter)}&dir=f&from={from_token}",
             access_token=self.tok,
         )
         self.assertEqual(channel.code, HTTPStatus.OK, channel.result)
 
-        return channel.json_body["chunk"]
-
-    def test_filter_relation_senders(self) -> None:
-        # Messages which second user reacted to.
-        filter = {"related_by_senders": [self.second_user_id]}
-        chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 1, chunk)
-        self.assertEqual(chunk[0]["event_id"], self.event_id_1)
-
-        # Messages which third user reacted to.
-        filter = {"related_by_senders": [self.third_user_id]}
-        chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 1, chunk)
-        self.assertEqual(chunk[0]["event_id"], self.event_id_2)
-
-        # Messages which either user reacted to.
-        filter = {"related_by_senders": [self.second_user_id, self.third_user_id]}
-        chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 2, chunk)
-        self.assertCountEqual(
-            [c["event_id"] for c in chunk], [self.event_id_1, self.event_id_2]
-        )
-
-    def test_filter_relation_type(self) -> None:
-        # Messages which have annotations.
-        filter = {"related_by_rel_types": [RelationTypes.ANNOTATION]}
-        chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 1, chunk)
-        self.assertEqual(chunk[0]["event_id"], self.event_id_1)
-
-        # Messages which have references.
-        filter = {"related_by_rel_types": [RelationTypes.REFERENCE]}
-        chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 1, chunk)
-        self.assertEqual(chunk[0]["event_id"], self.event_id_2)
-
-        # Messages which have either annotations or references.
-        filter = {
-            "related_by_rel_types": [
-                RelationTypes.ANNOTATION,
-                RelationTypes.REFERENCE,
-            ]
-        }
-        chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 2, chunk)
-        self.assertCountEqual(
-            [c["event_id"] for c in chunk], [self.event_id_1, self.event_id_2]
-        )
-
-    def test_filter_relation_senders_and_type(self) -> None:
-        # Messages which second user reacted to.
-        filter = {
-            "related_by_senders": [self.second_user_id],
-            "related_by_rel_types": [RelationTypes.ANNOTATION],
-        }
-        chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 1, chunk)
-        self.assertEqual(chunk[0]["event_id"], self.event_id_1)
+        return [ev["event_id"] for ev in channel.json_body["chunk"]]
 
 
 class ContextTestCase(unittest.HomeserverTestCase):
@@ -3615,3 +3537,60 @@ class ThreepidInviteTestCase(unittest.HomeserverTestCase):
         )
         self.assertEqual(channel.code, 400)
         self.assertEqual(channel.json_body["errcode"], "M_MISSING_PARAM")
+
+
+class TimestampLookupTestCase(unittest.HomeserverTestCase):
+    servlets = [
+        admin.register_servlets,
+        room.register_servlets,
+        login.register_servlets,
+    ]
+
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
+        self._storage_controllers = self.hs.get_storage_controllers()
+
+        self.room_owner = self.register_user("room_owner", "test")
+        self.room_owner_tok = self.login("room_owner", "test")
+
+    def _inject_outlier(self, room_id: str) -> EventBase:
+        event, _context = self.get_success(
+            create_event(
+                self.hs,
+                room_id=room_id,
+                type="m.test",
+                sender="@test_remote_user:remote",
+            )
+        )
+
+        event.internal_metadata.outlier = True
+        self.get_success(
+            self._storage_controllers.persistence.persist_event(
+                event, EventContext.for_outlier(self._storage_controllers)
+            )
+        )
+        return event
+
+    def test_no_outliers(self) -> None:
+        """
+        Test to make sure `/timestamp_to_event` does not return `outlier` events.
+        We're unable to determine whether an `outlier` is next to a gap so we
+        don't know whether it's actually the closest event. Instead, let's just
+        ignore `outliers` with this endpoint.
+
+        This test is really seeing that we choose the non-`outlier` event behind the
+        `outlier`. Since the gap checking logic considers the latest message in the room
+        as *not* next to a gap, asking over federation does not come into play here.
+        """
+        room_id = self.helper.create_room_as(self.room_owner, tok=self.room_owner_tok)
+
+        outlier_event = self._inject_outlier(room_id)
+
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{room_id}/timestamp_to_event?dir=b&ts={outlier_event.origin_server_ts}",
+            access_token=self.room_owner_tok,
+        )
+        self.assertEqual(HTTPStatus.OK, channel.code, msg=channel.json_body)
+
+        # Make sure the outlier event is not returned
+        self.assertNotEqual(channel.json_body["event_id"], outlier_event.event_id)
diff --git a/tests/rest/client/test_typing.py b/tests/rest/client/test_typing.py
index 61b66d7685..fdc433a8b5 100644
--- a/tests/rest/client/test_typing.py
+++ b/tests/rest/client/test_typing.py
@@ -59,7 +59,8 @@ class RoomTypingTestCase(unittest.HomeserverTestCase):
             self.event_source.get_new_events(
                 user=UserID.from_string(self.user_id),
                 from_key=0,
-                limit=None,
+                # Limit is unused.
+                limit=0,
                 room_ids=[self.room_id],
                 is_guest=False,
             )
diff --git a/tests/rest/client/utils.py b/tests/rest/client/utils.py
index c249a42bb6..8d6f2b6ff9 100644
--- a/tests/rest/client/utils.py
+++ b/tests/rest/client/utils.py
@@ -31,7 +31,6 @@ from typing import (
     Tuple,
     overload,
 )
-from unittest.mock import patch
 from urllib.parse import urlencode
 
 import attr
@@ -46,8 +45,19 @@ from synapse.server import HomeServer
 from synapse.types import JsonDict
 
 from tests.server import FakeChannel, FakeSite, make_request
-from tests.test_utils import FakeResponse
 from tests.test_utils.html_parsers import TestHtmlParser
+from tests.test_utils.oidc import FakeAuthorizationGrant, FakeOidcServer
+
+# an 'oidc_config' suitable for login_via_oidc.
+TEST_OIDC_ISSUER = "https://issuer.test/"
+TEST_OIDC_CONFIG = {
+    "enabled": True,
+    "issuer": TEST_OIDC_ISSUER,
+    "client_id": "test-client-id",
+    "client_secret": "test-client-secret",
+    "scopes": ["openid"],
+    "user_mapping_provider": {"config": {"localpart_template": "{{ user.sub }}"}},
+}
 
 
 @attr.s(auto_attribs=True)
@@ -400,6 +410,43 @@ class RestHelper:
 
         return channel.json_body
 
+    def get_event(
+        self,
+        room_id: str,
+        event_id: str,
+        tok: Optional[str] = None,
+        expect_code: int = HTTPStatus.OK,
+    ) -> JsonDict:
+        """Request a specific event from the server.
+
+        Args:
+            room_id: the room in which the event was sent.
+            event_id: the event's ID.
+            tok: the token to request the event with.
+            expect_code: the expected HTTP status for the response.
+
+        Returns:
+            The event as a dict.
+        """
+        path = f"/_matrix/client/v3/rooms/{room_id}/event/{event_id}"
+        if tok:
+            path = path + f"?access_token={tok}"
+
+        channel = make_request(
+            self.hs.get_reactor(),
+            self.site,
+            "GET",
+            path,
+        )
+
+        assert channel.code == expect_code, "Expected: %d, got: %d, resp: %r" % (
+            expect_code,
+            channel.code,
+            channel.result["body"],
+        )
+
+        return channel.json_body
+
     def _read_write_state(
         self,
         room_id: str,
@@ -543,12 +590,57 @@ class RestHelper:
 
         return channel.json_body
 
+    def whoami(
+        self,
+        access_token: str,
+        expect_code: Literal[HTTPStatus.OK, HTTPStatus.UNAUTHORIZED] = HTTPStatus.OK,
+    ) -> JsonDict:
+        """Perform a 'whoami' request, which can be a quick way to check for access
+        token validity
+
+        Args:
+            access_token: The user token to use during the request
+            expect_code: The return code to expect from attempting the whoami request
+        """
+        channel = make_request(
+            self.hs.get_reactor(),
+            self.site,
+            "GET",
+            "account/whoami",
+            access_token=access_token,
+        )
+
+        assert channel.code == expect_code, "Exepcted: %d, got %d, resp: %r" % (
+            expect_code,
+            channel.code,
+            channel.result["body"],
+        )
+
+        return channel.json_body
+
+    def fake_oidc_server(self, issuer: str = TEST_OIDC_ISSUER) -> FakeOidcServer:
+        """Create a ``FakeOidcServer``.
+
+        This can be used in conjuction with ``login_via_oidc``::
+
+            fake_oidc_server = self.helper.fake_oidc_server()
+            login_data, _ = self.helper.login_via_oidc(fake_oidc_server, "user")
+        """
+
+        return FakeOidcServer(
+            clock=self.hs.get_clock(),
+            issuer=issuer,
+        )
+
     def login_via_oidc(
         self,
+        fake_server: FakeOidcServer,
         remote_user_id: str,
+        with_sid: bool = False,
+        idp_id: Optional[str] = None,
         expected_status: int = 200,
-    ) -> JsonDict:
-        """Log in via OIDC
+    ) -> Tuple[JsonDict, FakeAuthorizationGrant]:
+        """Log in (as a new user) via OIDC
 
         Returns the result of the final token login.
 
@@ -560,7 +652,14 @@ class RestHelper:
         the normal places.
         """
         client_redirect_url = "https://x"
-        channel = self.auth_via_oidc({"sub": remote_user_id}, client_redirect_url)
+        userinfo = {"sub": remote_user_id}
+        channel, grant = self.auth_via_oidc(
+            fake_server,
+            userinfo,
+            client_redirect_url,
+            with_sid=with_sid,
+            idp_id=idp_id,
+        )
 
         # expect a confirmation page
         assert channel.code == HTTPStatus.OK, channel.result
@@ -585,14 +684,17 @@ class RestHelper:
         assert (
             channel.code == expected_status
         ), f"unexpected status in response: {channel.code}"
-        return channel.json_body
+        return channel.json_body, grant
 
     def auth_via_oidc(
         self,
+        fake_server: FakeOidcServer,
         user_info_dict: JsonDict,
         client_redirect_url: Optional[str] = None,
         ui_auth_session_id: Optional[str] = None,
-    ) -> FakeChannel:
+        with_sid: bool = False,
+        idp_id: Optional[str] = None,
+    ) -> Tuple[FakeChannel, FakeAuthorizationGrant]:
         """Perform an OIDC authentication flow via a mock OIDC provider.
 
         This can be used for either login or user-interactive auth.
@@ -616,6 +718,8 @@ class RestHelper:
                 the login redirect endpoint
             ui_auth_session_id: if set, we will perform a UI Auth flow. The session id
                 of the UI auth.
+            with_sid: if True, generates a random `sid` (OIDC session ID)
+            idp_id: if set, explicitely chooses one specific IDP
 
         Returns:
             A FakeChannel containing the result of calling the OIDC callback endpoint.
@@ -625,14 +729,17 @@ class RestHelper:
 
         cookies: Dict[str, str] = {}
 
-        # if we're doing a ui auth, hit the ui auth redirect endpoint
-        if ui_auth_session_id:
-            # can't set the client redirect url for UI Auth
-            assert client_redirect_url is None
-            oauth_uri = self.initiate_sso_ui_auth(ui_auth_session_id, cookies)
-        else:
-            # otherwise, hit the login redirect endpoint
-            oauth_uri = self.initiate_sso_login(client_redirect_url, cookies)
+        with fake_server.patch_homeserver(hs=self.hs):
+            # if we're doing a ui auth, hit the ui auth redirect endpoint
+            if ui_auth_session_id:
+                # can't set the client redirect url for UI Auth
+                assert client_redirect_url is None
+                oauth_uri = self.initiate_sso_ui_auth(ui_auth_session_id, cookies)
+            else:
+                # otherwise, hit the login redirect endpoint
+                oauth_uri = self.initiate_sso_login(
+                    client_redirect_url, cookies, idp_id=idp_id
+                )
 
         # we now have a URI for the OIDC IdP, but we skip that and go straight
         # back to synapse's OIDC callback resource. However, we do need the "state"
@@ -640,17 +747,21 @@ class RestHelper:
         # that synapse passes to the client.
 
         oauth_uri_path, _ = oauth_uri.split("?", 1)
-        assert oauth_uri_path == TEST_OIDC_AUTH_ENDPOINT, (
+        assert oauth_uri_path == fake_server.authorization_endpoint, (
             "unexpected SSO URI " + oauth_uri_path
         )
-        return self.complete_oidc_auth(oauth_uri, cookies, user_info_dict)
+        return self.complete_oidc_auth(
+            fake_server, oauth_uri, cookies, user_info_dict, with_sid=with_sid
+        )
 
     def complete_oidc_auth(
         self,
+        fake_serer: FakeOidcServer,
         oauth_uri: str,
         cookies: Mapping[str, str],
         user_info_dict: JsonDict,
-    ) -> FakeChannel:
+        with_sid: bool = False,
+    ) -> Tuple[FakeChannel, FakeAuthorizationGrant]:
         """Mock out an OIDC authentication flow
 
         Assumes that an OIDC auth has been initiated by one of initiate_sso_login or
@@ -661,50 +772,37 @@ class RestHelper:
         Requires the OIDC callback resource to be mounted at the normal place.
 
         Args:
+            fake_server: the fake OIDC server with which the auth should be done
             oauth_uri: the OIDC URI returned by synapse's redirect endpoint (ie,
                from initiate_sso_login or initiate_sso_ui_auth).
             cookies: the cookies set by synapse's redirect endpoint, which will be
                sent back to the callback endpoint.
             user_info_dict: the remote userinfo that the OIDC provider should present.
                 Typically this should be '{"sub": "<remote user id>"}'.
+            with_sid: if True, generates a random `sid` (OIDC session ID)
 
         Returns:
             A FakeChannel containing the result of calling the OIDC callback endpoint.
         """
         _, oauth_uri_qs = oauth_uri.split("?", 1)
         params = urllib.parse.parse_qs(oauth_uri_qs)
+
+        code, grant = fake_serer.start_authorization(
+            scope=params["scope"][0],
+            userinfo=user_info_dict,
+            client_id=params["client_id"][0],
+            redirect_uri=params["redirect_uri"][0],
+            nonce=params["nonce"][0],
+            with_sid=with_sid,
+        )
+        state = params["state"][0]
+
         callback_uri = "%s?%s" % (
             urllib.parse.urlparse(params["redirect_uri"][0]).path,
-            urllib.parse.urlencode({"state": params["state"][0], "code": "TEST_CODE"}),
-        )
-
-        # before we hit the callback uri, stub out some methods in the http client so
-        # that we don't have to handle full HTTPS requests.
-        # (expected url, json response) pairs, in the order we expect them.
-        expected_requests = [
-            # first we get a hit to the token endpoint, which we tell to return
-            # a dummy OIDC access token
-            (TEST_OIDC_TOKEN_ENDPOINT, {"access_token": "TEST"}),
-            # and then one to the user_info endpoint, which returns our remote user id.
-            (TEST_OIDC_USERINFO_ENDPOINT, user_info_dict),
-        ]
-
-        async def mock_req(
-            method: str,
-            uri: str,
-            data: Optional[dict] = None,
-            headers: Optional[Iterable[Tuple[AnyStr, AnyStr]]] = None,
-        ):
-            (expected_uri, resp_obj) = expected_requests.pop(0)
-            assert uri == expected_uri
-            resp = FakeResponse(
-                code=HTTPStatus.OK,
-                phrase=b"OK",
-                body=json.dumps(resp_obj).encode("utf-8"),
-            )
-            return resp
+            urllib.parse.urlencode({"state": state, "code": code}),
+        )
 
-        with patch.object(self.hs.get_proxied_http_client(), "request", mock_req):
+        with fake_serer.patch_homeserver(hs=self.hs):
             # now hit the callback URI with the right params and a made-up code
             channel = make_request(
                 self.hs.get_reactor(),
@@ -715,10 +813,13 @@ class RestHelper:
                     ("Cookie", "%s=%s" % (k, v)) for (k, v) in cookies.items()
                 ],
             )
-        return channel
+        return channel, grant
 
     def initiate_sso_login(
-        self, client_redirect_url: Optional[str], cookies: MutableMapping[str, str]
+        self,
+        client_redirect_url: Optional[str],
+        cookies: MutableMapping[str, str],
+        idp_id: Optional[str] = None,
     ) -> str:
         """Make a request to the login-via-sso redirect endpoint, and return the target
 
@@ -729,6 +830,7 @@ class RestHelper:
             client_redirect_url: the client redirect URL to pass to the login redirect
                 endpoint
             cookies: any cookies returned will be added to this dict
+            idp_id: if set, explicitely chooses one specific IDP
 
         Returns:
             the URI that the client gets redirected to (ie, the SSO server)
@@ -737,6 +839,12 @@ class RestHelper:
         if client_redirect_url:
             params["redirectUrl"] = client_redirect_url
 
+        uri = "/_matrix/client/r0/login/sso/redirect"
+        if idp_id is not None:
+            uri = f"{uri}/{idp_id}"
+
+        uri = f"{uri}?{urllib.parse.urlencode(params)}"
+
         # hit the redirect url (which should redirect back to the redirect url. This
         # is the easiest way of figuring out what the Host header ought to be set to
         # to keep Synapse happy.
@@ -744,7 +852,7 @@ class RestHelper:
             self.hs.get_reactor(),
             self.site,
             "GET",
-            "/_matrix/client/r0/login/sso/redirect?" + urllib.parse.urlencode(params),
+            uri,
         )
         assert channel.code == 302
 
@@ -806,21 +914,3 @@ class RestHelper:
         assert len(p.links) == 1, "not exactly one link in confirmation page"
         oauth_uri = p.links[0]
         return oauth_uri
-
-
-# an 'oidc_config' suitable for login_via_oidc.
-TEST_OIDC_AUTH_ENDPOINT = "https://issuer.test/auth"
-TEST_OIDC_TOKEN_ENDPOINT = "https://issuer.test/token"
-TEST_OIDC_USERINFO_ENDPOINT = "https://issuer.test/userinfo"
-TEST_OIDC_CONFIG = {
-    "enabled": True,
-    "discover": False,
-    "issuer": "https://issuer.test",
-    "client_id": "test-client-id",
-    "client_secret": "test-client-secret",
-    "scopes": ["profile"],
-    "authorization_endpoint": TEST_OIDC_AUTH_ENDPOINT,
-    "token_endpoint": TEST_OIDC_TOKEN_ENDPOINT,
-    "userinfo_endpoint": TEST_OIDC_USERINFO_ENDPOINT,
-    "user_mapping_provider": {"config": {"localpart_template": "{{ user.sub }}"}},
-}
diff --git a/tests/rest/key/v2/test_remote_key_resource.py b/tests/rest/key/v2/test_remote_key_resource.py
index ac0ac06b7e..2bb6e27d94 100644
--- a/tests/rest/key/v2/test_remote_key_resource.py
+++ b/tests/rest/key/v2/test_remote_key_resource.py
@@ -11,7 +11,6 @@
 # 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 urllib.parse
 from io import BytesIO, StringIO
 from typing import Any, Dict, Optional, Union
 from unittest.mock import Mock
@@ -26,7 +25,7 @@ from twisted.web.resource import NoResource, Resource
 
 from synapse.crypto.keyring import PerspectivesKeyFetcher
 from synapse.http.site import SynapseRequest
-from synapse.rest.key.v2 import KeyApiV2Resource
+from synapse.rest.key.v2 import KeyResource
 from synapse.server import HomeServer
 from synapse.storage.keys import FetchKeyResult
 from synapse.types import JsonDict
@@ -46,7 +45,7 @@ class BaseRemoteKeyResourceTestCase(unittest.HomeserverTestCase):
 
     def create_test_resource(self) -> Resource:
         return create_resource_tree(
-            {"/_matrix/key/v2": KeyApiV2Resource(self.hs)}, root_resource=NoResource()
+            {"/_matrix/key/v2": KeyResource(self.hs)}, root_resource=NoResource()
         )
 
     def expect_outgoing_key_request(
@@ -65,9 +64,7 @@ class BaseRemoteKeyResourceTestCase(unittest.HomeserverTestCase):
             self.assertTrue(ignore_backoff)
             self.assertEqual(destination, server_name)
             key_id = "%s:%s" % (signing_key.alg, signing_key.version)
-            self.assertEqual(
-                path, "/_matrix/key/v2/server/%s" % (urllib.parse.quote(key_id),)
-            )
+            self.assertEqual(path, "/_matrix/key/v2/server")
 
             response = {
                 "server_name": server_name,