diff --git a/changelog.d/14988.misc b/changelog.d/14988.misc
new file mode 100644
index 000000000..93ceaeafc
--- /dev/null
+++ b/changelog.d/14988.misc
@@ -0,0 +1 @@
+Improve type hints.
diff --git a/mypy.ini b/mypy.ini
index 93de1c97e..11e683b70 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -32,9 +32,6 @@ exclude = (?x)
    |synapse/storage/databases/main/cache.py
    |synapse/storage/schema/
 
-   |tests/http/federation/test_matrix_federation_agent.py
-   |tests/http/federation/test_srv_resolver.py
-   |tests/http/test_proxyagent.py
    |tests/module_api/test_api.py
    |tests/rest/media/v1/test_media_storage.py
    |tests/server.py
@@ -92,6 +89,9 @@ disallow_untyped_defs = True
 [mypy-tests.handlers.*]
 disallow_untyped_defs = True
 
+[mypy-tests.http.*]
+disallow_untyped_defs = True
+
 [mypy-tests.logging.*]
 disallow_untyped_defs = True
 
diff --git a/synapse/http/client.py b/synapse/http/client.py
index 4eb740c04..a05f29793 100644
--- a/synapse/http/client.py
+++ b/synapse/http/client.py
@@ -44,6 +44,7 @@ from twisted.internet.interfaces import (
     IAddress,
     IDelayedCall,
     IHostResolution,
+    IReactorCore,
     IReactorPluggableNameResolver,
     IReactorTime,
     IResolutionReceiver,
@@ -226,7 +227,9 @@ class _IPBlacklistingResolver:
         return recv
 
 
-@implementer(ISynapseReactor)
+# ISynapseReactor implies IReactorCore, but explicitly marking it this as an implementer
+# of IReactorCore seems to keep mypy-zope happier.
+@implementer(IReactorCore, ISynapseReactor)
 class BlacklistingReactorWrapper:
     """
     A Reactor wrapper which will prevent DNS resolution to blacklisted IP
diff --git a/synapse/http/proxyagent.py b/synapse/http/proxyagent.py
index 18899bc6d..94ef737b9 100644
--- a/synapse/http/proxyagent.py
+++ b/synapse/http/proxyagent.py
@@ -38,7 +38,6 @@ from twisted.web.iweb import IAgent, IBodyProducer, IPolicyForHTTPS, IResponse
 
 from synapse.http import redact_uri
 from synapse.http.connectproxyclient import HTTPConnectProxyEndpoint, ProxyCredentials
-from synapse.types import ISynapseReactor
 
 logger = logging.getLogger(__name__)
 
@@ -84,7 +83,7 @@ class ProxyAgent(_AgentBase):
     def __init__(
         self,
         reactor: IReactorCore,
-        proxy_reactor: Optional[ISynapseReactor] = None,
+        proxy_reactor: Optional[IReactorCore] = None,
         contextFactory: Optional[IPolicyForHTTPS] = None,
         connectTimeout: Optional[float] = None,
         bindAddress: Optional[bytes] = None,
diff --git a/tests/http/__init__.py b/tests/http/__init__.py
index 093537ade..528cdee34 100644
--- a/tests/http/__init__.py
+++ b/tests/http/__init__.py
@@ -19,13 +19,15 @@ from zope.interface import implementer
 
 from OpenSSL import SSL
 from OpenSSL.SSL import Connection
+from twisted.internet.address import IPv4Address
 from twisted.internet.interfaces import IOpenSSLServerConnectionCreator
 from twisted.internet.ssl import Certificate, trustRootFromCertificates
+from twisted.protocols.tls import TLSMemoryBIOProtocol
 from twisted.web.client import BrowserLikePolicyForHTTPS  # noqa: F401
 from twisted.web.iweb import IPolicyForHTTPS  # noqa: F401
 
 
-def get_test_https_policy():
+def get_test_https_policy() -> BrowserLikePolicyForHTTPS:
     """Get a test IPolicyForHTTPS which trusts the test CA cert
 
     Returns:
@@ -39,7 +41,7 @@ def get_test_https_policy():
     return BrowserLikePolicyForHTTPS(trustRoot=trust_root)
 
 
-def get_test_ca_cert_file():
+def get_test_ca_cert_file() -> str:
     """Get the path to the test CA cert
 
     The keypair is generated with:
@@ -51,7 +53,7 @@ def get_test_ca_cert_file():
     return os.path.join(os.path.dirname(__file__), "ca.crt")
 
 
-def get_test_key_file():
+def get_test_key_file() -> str:
     """get the path to the test key
 
     The key file is made with:
@@ -137,15 +139,20 @@ class TestServerTLSConnectionFactory:
     """An SSL connection creator which returns connections which present a certificate
     signed by our test CA."""
 
-    def __init__(self, sanlist):
+    def __init__(self, sanlist: List[bytes]):
         """
         Args:
-            sanlist: list[bytes]: a list of subjectAltName values for the cert
+            sanlist: a list of subjectAltName values for the cert
         """
         self._cert_file = create_test_cert_file(sanlist)
 
-    def serverConnectionForTLS(self, tlsProtocol):
+    def serverConnectionForTLS(self, tlsProtocol: TLSMemoryBIOProtocol) -> Connection:
         ctx = SSL.Context(SSL.SSLv23_METHOD)
         ctx.use_certificate_file(self._cert_file)
         ctx.use_privatekey_file(get_test_key_file())
         return Connection(ctx, None)
+
+
+# A dummy address, useful for tests that use FakeTransport and don't care about where
+# packets are going to/coming from.
+dummy_address = IPv4Address("TCP", "127.0.0.1", 80)
diff --git a/tests/http/federation/test_matrix_federation_agent.py b/tests/http/federation/test_matrix_federation_agent.py
index 992d8f94f..acfdcd3bc 100644
--- a/tests/http/federation/test_matrix_federation_agent.py
+++ b/tests/http/federation/test_matrix_federation_agent.py
@@ -14,7 +14,7 @@
 import base64
 import logging
 import os
-from typing import Iterable, Optional
+from typing import Any, Awaitable, Callable, Generator, List, Optional, cast
 from unittest.mock import Mock, patch
 
 import treq
@@ -24,14 +24,19 @@ from zope.interface import implementer
 
 from twisted.internet import defer
 from twisted.internet._sslverify import ClientTLSOptions, OpenSSLCertificateOptions
-from twisted.internet.interfaces import IProtocolFactory
+from twisted.internet.defer import Deferred
+from twisted.internet.endpoints import _WrappingProtocol
+from twisted.internet.interfaces import (
+    IOpenSSLClientConnectionCreator,
+    IProtocolFactory,
+)
 from twisted.internet.protocol import Factory
 from twisted.protocols.tls import TLSMemoryBIOFactory, TLSMemoryBIOProtocol
 from twisted.web._newclient import ResponseNeverReceived
 from twisted.web.client import Agent
 from twisted.web.http import HTTPChannel, Request
 from twisted.web.http_headers import Headers
-from twisted.web.iweb import IPolicyForHTTPS
+from twisted.web.iweb import IPolicyForHTTPS, IResponse
 
 from synapse.config.homeserver import HomeServerConfig
 from synapse.crypto.context_factory import FederationPolicyForHTTPS
@@ -42,11 +47,21 @@ from synapse.http.federation.well_known_resolver import (
     WellKnownResolver,
     _cache_period_from_headers,
 )
-from synapse.logging.context import SENTINEL_CONTEXT, LoggingContext, current_context
+from synapse.logging.context import (
+    SENTINEL_CONTEXT,
+    LoggingContext,
+    LoggingContextOrSentinel,
+    current_context,
+)
+from synapse.types import ISynapseReactor
 from synapse.util.caches.ttlcache import TTLCache
 
 from tests import unittest
-from tests.http import TestServerTLSConnectionFactory, get_test_ca_cert_file
+from tests.http import (
+    TestServerTLSConnectionFactory,
+    dummy_address,
+    get_test_ca_cert_file,
+)
 from tests.server import FakeTransport, ThreadedMemoryReactorClock
 from tests.utils import default_config
 
@@ -54,15 +69,17 @@ logger = logging.getLogger(__name__)
 
 
 # Once Async Mocks or lambdas are supported this can go away.
-def generate_resolve_service(result):
-    async def resolve_service(_):
+def generate_resolve_service(
+    result: List[Server],
+) -> Callable[[Any], Awaitable[List[Server]]]:
+    async def resolve_service(_: Any) -> List[Server]:
         return result
 
     return resolve_service
 
 
 class MatrixFederationAgentTests(unittest.TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
         self.reactor = ThreadedMemoryReactorClock()
 
         self.mock_resolver = Mock()
@@ -75,8 +92,12 @@ class MatrixFederationAgentTests(unittest.TestCase):
 
         self.tls_factory = FederationPolicyForHTTPS(config)
 
-        self.well_known_cache = TTLCache("test_cache", timer=self.reactor.seconds)
-        self.had_well_known_cache = TTLCache("test_cache", timer=self.reactor.seconds)
+        self.well_known_cache: TTLCache[bytes, Optional[bytes]] = TTLCache(
+            "test_cache", timer=self.reactor.seconds
+        )
+        self.had_well_known_cache: TTLCache[bytes, bool] = TTLCache(
+            "test_cache", timer=self.reactor.seconds
+        )
         self.well_known_resolver = WellKnownResolver(
             self.reactor,
             Agent(self.reactor, contextFactory=self.tls_factory),
@@ -89,8 +110,8 @@ class MatrixFederationAgentTests(unittest.TestCase):
         self,
         client_factory: IProtocolFactory,
         ssl: bool = True,
-        expected_sni: bytes = None,
-        tls_sanlist: Optional[Iterable[bytes]] = None,
+        expected_sni: Optional[bytes] = None,
+        tls_sanlist: Optional[List[bytes]] = None,
     ) -> HTTPChannel:
         """Builds a test server, and completes the outgoing client connection
         Args:
@@ -116,8 +137,8 @@ class MatrixFederationAgentTests(unittest.TestCase):
         if ssl:
             server_factory = _wrap_server_factory_for_tls(server_factory, tls_sanlist)
 
-        server_protocol = server_factory.buildProtocol(None)
-
+        server_protocol = server_factory.buildProtocol(dummy_address)
+        assert server_protocol is not None
         # now, tell the client protocol factory to build the client protocol (it will be a
         # _WrappingProtocol, around a TLSMemoryBIOProtocol, around an
         # HTTP11ClientProtocol) and wire the output of said protocol up to the server via
@@ -125,7 +146,8 @@ class MatrixFederationAgentTests(unittest.TestCase):
         #
         # Normally this would be done by the TCP socket code in Twisted, but we are
         # stubbing that out here.
-        client_protocol = client_factory.buildProtocol(None)
+        client_protocol = client_factory.buildProtocol(dummy_address)
+        assert isinstance(client_protocol, _WrappingProtocol)
         client_protocol.makeConnection(
             FakeTransport(server_protocol, self.reactor, client_protocol)
         )
@@ -136,6 +158,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         )
 
         if ssl:
+            assert isinstance(server_protocol, TLSMemoryBIOProtocol)
             # fish the test server back out of the server-side TLS protocol.
             http_protocol = server_protocol.wrappedProtocol
             # grab a hold of the TLS connection, in case it gets torn down
@@ -144,6 +167,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
             http_protocol = server_protocol
             tls_connection = None
 
+        assert isinstance(http_protocol, HTTPChannel)
         # give the reactor a pump to get the TLS juices flowing (if needed)
         self.reactor.advance(0)
 
@@ -159,12 +183,14 @@ class MatrixFederationAgentTests(unittest.TestCase):
         return http_protocol
 
     @defer.inlineCallbacks
-    def _make_get_request(self, uri: bytes):
+    def _make_get_request(
+        self, uri: bytes
+    ) -> Generator["Deferred[object]", object, IResponse]:
         """
         Sends a simple GET request via the agent, and checks its logcontext management
         """
         with LoggingContext("one") as context:
-            fetch_d = self.agent.request(b"GET", uri)
+            fetch_d: Deferred[IResponse] = self.agent.request(b"GET", uri)
 
             # Nothing happened yet
             self.assertNoResult(fetch_d)
@@ -172,8 +198,9 @@ class MatrixFederationAgentTests(unittest.TestCase):
             # should have reset logcontext to the sentinel
             _check_logcontext(SENTINEL_CONTEXT)
 
+            fetch_res: IResponse
             try:
-                fetch_res = yield fetch_d
+                fetch_res = yield fetch_d  # type: ignore[misc, assignment]
                 return fetch_res
             except Exception as e:
                 logger.info("Fetch of %s failed: %s", uri.decode("ascii"), e)
@@ -216,7 +243,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         request: Request,
         content: bytes,
         headers: Optional[dict] = None,
-    ):
+    ) -> None:
         """Check that an incoming request looks like a valid .well-known request, and
         send back the response.
         """
@@ -237,16 +264,16 @@ class MatrixFederationAgentTests(unittest.TestCase):
         because it is created too early during setUp
         """
         return MatrixFederationAgent(
-            reactor=self.reactor,
+            reactor=cast(ISynapseReactor, self.reactor),
             tls_client_options_factory=self.tls_factory,
-            user_agent="test-agent",  # Note that this is unused since _well_known_resolver is provided.
+            user_agent=b"test-agent",  # Note that this is unused since _well_known_resolver is provided.
             ip_whitelist=IPSet(),
             ip_blacklist=IPSet(),
             _srv_resolver=self.mock_resolver,
             _well_known_resolver=self.well_known_resolver,
         )
 
-    def test_get(self):
+    def test_get(self) -> None:
         """happy-path test of a GET request with an explicit port"""
         self._do_get()
 
@@ -254,11 +281,11 @@ class MatrixFederationAgentTests(unittest.TestCase):
         os.environ,
         {"https_proxy": "proxy.com", "no_proxy": "testserv"},
     )
-    def test_get_bypass_proxy(self):
+    def test_get_bypass_proxy(self) -> None:
         """test of a GET request with an explicit port and bypass proxy"""
         self._do_get()
 
-    def _do_get(self):
+    def _do_get(self) -> None:
         """test of a GET request with an explicit port"""
         self.agent = self._make_agent()
 
@@ -318,7 +345,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
     @patch.dict(
         os.environ, {"https_proxy": "http://proxy.com", "no_proxy": "unused.com"}
     )
-    def test_get_via_http_proxy(self):
+    def test_get_via_http_proxy(self) -> None:
         """test for federation request through a http proxy"""
         self._do_get_via_proxy(expect_proxy_ssl=False, expected_auth_credentials=None)
 
@@ -326,7 +353,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         os.environ,
         {"https_proxy": "http://user:pass@proxy.com", "no_proxy": "unused.com"},
     )
-    def test_get_via_http_proxy_with_auth(self):
+    def test_get_via_http_proxy_with_auth(self) -> None:
         """test for federation request through a http proxy with authentication"""
         self._do_get_via_proxy(
             expect_proxy_ssl=False, expected_auth_credentials=b"user:pass"
@@ -335,7 +362,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
     @patch.dict(
         os.environ, {"https_proxy": "https://proxy.com", "no_proxy": "unused.com"}
     )
-    def test_get_via_https_proxy(self):
+    def test_get_via_https_proxy(self) -> None:
         """test for federation request through a https proxy"""
         self._do_get_via_proxy(expect_proxy_ssl=True, expected_auth_credentials=None)
 
@@ -343,7 +370,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         os.environ,
         {"https_proxy": "https://user:pass@proxy.com", "no_proxy": "unused.com"},
     )
-    def test_get_via_https_proxy_with_auth(self):
+    def test_get_via_https_proxy_with_auth(self) -> None:
         """test for federation request through a https proxy with authentication"""
         self._do_get_via_proxy(
             expect_proxy_ssl=True, expected_auth_credentials=b"user:pass"
@@ -353,7 +380,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         self,
         expect_proxy_ssl: bool = False,
         expected_auth_credentials: Optional[bytes] = None,
-    ):
+    ) -> None:
         """Send a https federation request via an agent and check that it is correctly
             received at the proxy and client. The proxy can use either http or https.
         Args:
@@ -418,10 +445,12 @@ class MatrixFederationAgentTests(unittest.TestCase):
         # now we make another test server to act as the upstream HTTP server.
         server_ssl_protocol = _wrap_server_factory_for_tls(
             _get_test_protocol_factory()
-        ).buildProtocol(None)
+        ).buildProtocol(dummy_address)
+        assert isinstance(server_ssl_protocol, TLSMemoryBIOProtocol)
 
         # Tell the HTTP server to send outgoing traffic back via the proxy's transport.
         proxy_server_transport = proxy_server.transport
+        assert proxy_server_transport is not None
         server_ssl_protocol.makeConnection(proxy_server_transport)
 
         # ... and replace the protocol on the proxy's transport with the
@@ -451,6 +480,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
 
         # now there should be a pending request
         http_server = server_ssl_protocol.wrappedProtocol
+        assert isinstance(http_server, HTTPChannel)
         self.assertEqual(len(http_server.requests), 1)
 
         request = http_server.requests[0]
@@ -491,7 +521,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         json = self.successResultOf(treq.json_content(response))
         self.assertEqual(json, {"a": 1})
 
-    def test_get_ip_address(self):
+    def test_get_ip_address(self) -> None:
         """
         Test the behaviour when the server name contains an explicit IP (with no port)
         """
@@ -526,7 +556,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         self.reactor.pump((0.1,))
         self.successResultOf(test_d)
 
-    def test_get_ipv6_address(self):
+    def test_get_ipv6_address(self) -> None:
         """
         Test the behaviour when the server name contains an explicit IPv6 address
         (with no port)
@@ -562,7 +592,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         self.reactor.pump((0.1,))
         self.successResultOf(test_d)
 
-    def test_get_ipv6_address_with_port(self):
+    def test_get_ipv6_address_with_port(self) -> None:
         """
         Test the behaviour when the server name contains an explicit IPv6 address
         (with explicit port)
@@ -598,7 +628,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         self.reactor.pump((0.1,))
         self.successResultOf(test_d)
 
-    def test_get_hostname_bad_cert(self):
+    def test_get_hostname_bad_cert(self) -> None:
         """
         Test the behaviour when the certificate on the server doesn't match the hostname
         """
@@ -651,7 +681,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         failure_reason = e.value.reasons[0]
         self.assertIsInstance(failure_reason.value, VerificationError)
 
-    def test_get_ip_address_bad_cert(self):
+    def test_get_ip_address_bad_cert(self) -> None:
         """
         Test the behaviour when the server name contains an explicit IP, but
         the server cert doesn't cover it
@@ -684,7 +714,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         failure_reason = e.value.reasons[0]
         self.assertIsInstance(failure_reason.value, VerificationError)
 
-    def test_get_no_srv_no_well_known(self):
+    def test_get_no_srv_no_well_known(self) -> None:
         """
         Test the behaviour when the server name has no port, no SRV, and no well-known
         """
@@ -740,7 +770,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         self.reactor.pump((0.1,))
         self.successResultOf(test_d)
 
-    def test_get_well_known(self):
+    def test_get_well_known(self) -> None:
         """Test the behaviour when the .well-known delegates elsewhere"""
         self.agent = self._make_agent()
 
@@ -802,7 +832,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         self.well_known_cache.expire()
         self.assertNotIn(b"testserv", self.well_known_cache)
 
-    def test_get_well_known_redirect(self):
+    def test_get_well_known_redirect(self) -> None:
         """Test the behaviour when the server name has no port and no SRV record, but
         the .well-known has a 300 redirect
         """
@@ -892,7 +922,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         self.well_known_cache.expire()
         self.assertNotIn(b"testserv", self.well_known_cache)
 
-    def test_get_invalid_well_known(self):
+    def test_get_invalid_well_known(self) -> None:
         """
         Test the behaviour when the server name has an *invalid* well-known (and no SRV)
         """
@@ -945,7 +975,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         self.reactor.pump((0.1,))
         self.successResultOf(test_d)
 
-    def test_get_well_known_unsigned_cert(self):
+    def test_get_well_known_unsigned_cert(self) -> None:
         """Test the behaviour when the .well-known server presents a cert
         not signed by a CA
         """
@@ -969,7 +999,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
             ip_blacklist=IPSet(),
             _srv_resolver=self.mock_resolver,
             _well_known_resolver=WellKnownResolver(
-                self.reactor,
+                cast(ISynapseReactor, self.reactor),
                 Agent(self.reactor, contextFactory=tls_factory),
                 b"test-agent",
                 well_known_cache=self.well_known_cache,
@@ -999,7 +1029,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
             b"_matrix._tcp.testserv"
         )
 
-    def test_get_hostname_srv(self):
+    def test_get_hostname_srv(self) -> None:
         """
         Test the behaviour when there is a single SRV record
         """
@@ -1041,7 +1071,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         self.reactor.pump((0.1,))
         self.successResultOf(test_d)
 
-    def test_get_well_known_srv(self):
+    def test_get_well_known_srv(self) -> None:
         """Test the behaviour when the .well-known redirects to a place where there
         is a SRV.
         """
@@ -1101,7 +1131,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         self.reactor.pump((0.1,))
         self.successResultOf(test_d)
 
-    def test_idna_servername(self):
+    def test_idna_servername(self) -> None:
         """test the behaviour when the server name has idna chars in"""
         self.agent = self._make_agent()
 
@@ -1163,7 +1193,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         self.reactor.pump((0.1,))
         self.successResultOf(test_d)
 
-    def test_idna_srv_target(self):
+    def test_idna_srv_target(self) -> None:
         """test the behaviour when the target of a SRV record has idna chars"""
         self.agent = self._make_agent()
 
@@ -1206,7 +1236,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         self.reactor.pump((0.1,))
         self.successResultOf(test_d)
 
-    def test_well_known_cache(self):
+    def test_well_known_cache(self) -> None:
         self.reactor.lookups["testserv"] = "1.2.3.4"
 
         fetch_d = defer.ensureDeferred(
@@ -1262,7 +1292,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         r = self.successResultOf(fetch_d)
         self.assertEqual(r.delegated_server, b"other-server")
 
-    def test_well_known_cache_with_temp_failure(self):
+    def test_well_known_cache_with_temp_failure(self) -> None:
         """Test that we refetch well-known before the cache expires, and that
         it ignores transient errors.
         """
@@ -1341,7 +1371,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         r = self.successResultOf(fetch_d)
         self.assertEqual(r.delegated_server, None)
 
-    def test_well_known_too_large(self):
+    def test_well_known_too_large(self) -> None:
         """A well-known query that returns a result which is too large should be rejected."""
         self.reactor.lookups["testserv"] = "1.2.3.4"
 
@@ -1367,7 +1397,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
         r = self.successResultOf(fetch_d)
         self.assertIsNone(r.delegated_server)
 
-    def test_srv_fallbacks(self):
+    def test_srv_fallbacks(self) -> None:
         """Test that other SRV results are tried if the first one fails."""
         self.agent = self._make_agent()
 
@@ -1427,7 +1457,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
 
 
 class TestCachePeriodFromHeaders(unittest.TestCase):
-    def test_cache_control(self):
+    def test_cache_control(self) -> None:
         # uppercase
         self.assertEqual(
             _cache_period_from_headers(
@@ -1464,7 +1494,7 @@ class TestCachePeriodFromHeaders(unittest.TestCase):
             0,
         )
 
-    def test_expires(self):
+    def test_expires(self) -> None:
         self.assertEqual(
             _cache_period_from_headers(
                 Headers({b"Expires": [b"Wed, 30 Jan 2019 07:35:33 GMT"]}),
@@ -1491,14 +1521,14 @@ class TestCachePeriodFromHeaders(unittest.TestCase):
         self.assertEqual(_cache_period_from_headers(Headers({b"Expires": [b"0"]})), 0)
 
 
-def _check_logcontext(context):
+def _check_logcontext(context: LoggingContextOrSentinel) -> None:
     current = current_context()
     if current is not context:
         raise AssertionError("Expected logcontext %s but was %s" % (context, current))
 
 
 def _wrap_server_factory_for_tls(
-    factory: IProtocolFactory, sanlist: Iterable[bytes] = None
+    factory: IProtocolFactory, sanlist: Optional[List[bytes]] = None
 ) -> IProtocolFactory:
     """Wrap an existing Protocol Factory with a test TLSMemoryBIOFactory
     The resultant factory will create a TLS server which presents a certificate
@@ -1537,7 +1567,7 @@ def _get_test_protocol_factory() -> IProtocolFactory:
     return server_factory
 
 
-def _log_request(request: str):
+def _log_request(request: str) -> None:
     """Implements Factory.log, which is expected by Request.finish"""
     logger.info(f"Completed request {request}")
 
@@ -1547,6 +1577,8 @@ class TrustingTLSPolicyForHTTPS:
     """An IPolicyForHTTPS which checks that the certificate belongs to the
     right server, but doesn't check the certificate chain."""
 
-    def creatorForNetloc(self, hostname, port):
+    def creatorForNetloc(
+        self, hostname: bytes, port: int
+    ) -> IOpenSSLClientConnectionCreator:
         certificateOptions = OpenSSLCertificateOptions()
         return ClientTLSOptions(hostname, certificateOptions.getContext())
diff --git a/tests/http/federation/test_srv_resolver.py b/tests/http/federation/test_srv_resolver.py
index 77ce8432a..7748f56ee 100644
--- a/tests/http/federation/test_srv_resolver.py
+++ b/tests/http/federation/test_srv_resolver.py
@@ -12,7 +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.
-
+from typing import Dict, Generator, List, Tuple, cast
 from unittest.mock import Mock
 
 from twisted.internet import defer
@@ -20,7 +20,7 @@ from twisted.internet.defer import Deferred
 from twisted.internet.error import ConnectError
 from twisted.names import dns, error
 
-from synapse.http.federation.srv_resolver import SrvResolver
+from synapse.http.federation.srv_resolver import Server, SrvResolver
 from synapse.logging.context import LoggingContext, current_context
 
 from tests import unittest
@@ -28,7 +28,7 @@ from tests.utils import MockClock
 
 
 class SrvResolverTestCase(unittest.TestCase):
-    def test_resolve(self):
+    def test_resolve(self) -> None:
         dns_client_mock = Mock()
 
         service_name = b"test_service.example.com"
@@ -38,18 +38,19 @@ class SrvResolverTestCase(unittest.TestCase):
             type=dns.SRV, payload=dns.Record_SRV(target=host_name)
         )
 
-        result_deferred = Deferred()
+        result_deferred: "Deferred[Tuple[List[dns.RRHeader], None, None]]" = Deferred()
         dns_client_mock.lookupService.return_value = result_deferred
 
-        cache = {}
+        cache: Dict[bytes, List[Server]] = {}
         resolver = SrvResolver(dns_client=dns_client_mock, cache=cache)
 
         @defer.inlineCallbacks
-        def do_lookup():
+        def do_lookup() -> Generator["Deferred[object]", object, List[Server]]:
 
             with LoggingContext("one") as ctx:
                 resolve_d = resolver.resolve_service(service_name)
-                result = yield defer.ensureDeferred(resolve_d)
+                result: List[Server]
+                result = yield defer.ensureDeferred(resolve_d)  # type: ignore[assignment]
 
                 # should have restored our context
                 self.assertIs(current_context(), ctx)
@@ -70,7 +71,9 @@ class SrvResolverTestCase(unittest.TestCase):
         self.assertEqual(servers[0].host, host_name)
 
     @defer.inlineCallbacks
-    def test_from_cache_expired_and_dns_fail(self):
+    def test_from_cache_expired_and_dns_fail(
+        self,
+    ) -> Generator["Deferred[object]", object, None]:
         dns_client_mock = Mock()
         dns_client_mock.lookupService.return_value = defer.fail(error.DNSServerError())
 
@@ -81,10 +84,13 @@ class SrvResolverTestCase(unittest.TestCase):
         entry.priority = 0
         entry.weight = 0
 
-        cache = {service_name: [entry]}
+        cache = {service_name: [cast(Server, entry)]}
         resolver = SrvResolver(dns_client=dns_client_mock, cache=cache)
 
-        servers = yield defer.ensureDeferred(resolver.resolve_service(service_name))
+        servers: List[Server]
+        servers = yield defer.ensureDeferred(
+            resolver.resolve_service(service_name)
+        )  # type: ignore[assignment]
 
         dns_client_mock.lookupService.assert_called_once_with(service_name)
 
@@ -92,7 +98,7 @@ class SrvResolverTestCase(unittest.TestCase):
         self.assertEqual(servers, cache[service_name])
 
     @defer.inlineCallbacks
-    def test_from_cache(self):
+    def test_from_cache(self) -> Generator["Deferred[object]", object, None]:
         clock = MockClock()
 
         dns_client_mock = Mock(spec_set=["lookupService"])
@@ -105,12 +111,15 @@ class SrvResolverTestCase(unittest.TestCase):
         entry.priority = 0
         entry.weight = 0
 
-        cache = {service_name: [entry]}
+        cache = {service_name: [cast(Server, entry)]}
         resolver = SrvResolver(
             dns_client=dns_client_mock, cache=cache, get_time=clock.time
         )
 
-        servers = yield defer.ensureDeferred(resolver.resolve_service(service_name))
+        servers: List[Server]
+        servers = yield defer.ensureDeferred(
+            resolver.resolve_service(service_name)
+        )  # type: ignore[assignment]
 
         self.assertFalse(dns_client_mock.lookupService.called)
 
@@ -118,45 +127,48 @@ class SrvResolverTestCase(unittest.TestCase):
         self.assertEqual(servers, cache[service_name])
 
     @defer.inlineCallbacks
-    def test_empty_cache(self):
+    def test_empty_cache(self) -> Generator["Deferred[object]", object, None]:
         dns_client_mock = Mock()
 
         dns_client_mock.lookupService.return_value = defer.fail(error.DNSServerError())
 
         service_name = b"test_service.example.com"
 
-        cache = {}
+        cache: Dict[bytes, List[Server]] = {}
         resolver = SrvResolver(dns_client=dns_client_mock, cache=cache)
 
         with self.assertRaises(error.DNSServerError):
             yield defer.ensureDeferred(resolver.resolve_service(service_name))
 
     @defer.inlineCallbacks
-    def test_name_error(self):
+    def test_name_error(self) -> Generator["Deferred[object]", object, None]:
         dns_client_mock = Mock()
 
         dns_client_mock.lookupService.return_value = defer.fail(error.DNSNameError())
 
         service_name = b"test_service.example.com"
 
-        cache = {}
+        cache: Dict[bytes, List[Server]] = {}
         resolver = SrvResolver(dns_client=dns_client_mock, cache=cache)
 
-        servers = yield defer.ensureDeferred(resolver.resolve_service(service_name))
+        servers: List[Server]
+        servers = yield defer.ensureDeferred(
+            resolver.resolve_service(service_name)
+        )  # type: ignore[assignment]
 
         self.assertEqual(len(servers), 0)
         self.assertEqual(len(cache), 0)
 
-    def test_disabled_service(self):
+    def test_disabled_service(self) -> None:
         """
         test the behaviour when there is a single record which is ".".
         """
         service_name = b"test_service.example.com"
 
-        lookup_deferred = Deferred()
+        lookup_deferred: "Deferred[Tuple[List[dns.RRHeader], None, None]]" = Deferred()
         dns_client_mock = Mock()
         dns_client_mock.lookupService.return_value = lookup_deferred
-        cache = {}
+        cache: Dict[bytes, List[Server]] = {}
         resolver = SrvResolver(dns_client=dns_client_mock, cache=cache)
 
         # Old versions of Twisted don't have an ensureDeferred in failureResultOf.
@@ -173,16 +185,16 @@ class SrvResolverTestCase(unittest.TestCase):
 
         self.failureResultOf(resolve_d, ConnectError)
 
-    def test_non_srv_answer(self):
+    def test_non_srv_answer(self) -> None:
         """
         test the behaviour when the dns server gives us a spurious non-SRV response
         """
         service_name = b"test_service.example.com"
 
-        lookup_deferred = Deferred()
+        lookup_deferred: "Deferred[Tuple[List[dns.RRHeader], None, None]]" = Deferred()
         dns_client_mock = Mock()
         dns_client_mock.lookupService.return_value = lookup_deferred
-        cache = {}
+        cache: Dict[bytes, List[Server]] = {}
         resolver = SrvResolver(dns_client=dns_client_mock, cache=cache)
 
         # Old versions of Twisted don't have an ensureDeferred in successResultOf.
diff --git a/tests/http/server/_base.py b/tests/http/server/_base.py
index 5071f8357..36472e57a 100644
--- a/tests/http/server/_base.py
+++ b/tests/http/server/_base.py
@@ -556,6 +556,6 @@ def _get_stack_frame_method_name(frame_info: inspect.FrameInfo) -> str:
     return method_name
 
 
-def _hash_stack(stack: List[inspect.FrameInfo]):
+def _hash_stack(stack: List[inspect.FrameInfo]) -> Tuple[str, ...]:
     """Turns a stack into a hashable value that can be put into a set."""
     return tuple(_format_stack_frame(frame) for frame in stack)
diff --git a/tests/http/test_additional_resource.py b/tests/http/test_additional_resource.py
index 391196425..ec6aacf23 100644
--- a/tests/http/test_additional_resource.py
+++ b/tests/http/test_additional_resource.py
@@ -11,28 +11,34 @@
 # 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 Any
 
+from twisted.web.server import Request
 
 from synapse.http.additional_resource import AdditionalResource
 from synapse.http.server import respond_with_json
+from synapse.http.site import SynapseRequest
+from synapse.types import JsonDict
 
 from tests.server import FakeSite, make_request
 from tests.unittest import HomeserverTestCase
 
 
 class _AsyncTestCustomEndpoint:
-    def __init__(self, config, module_api):
+    def __init__(self, config: JsonDict, module_api: Any) -> None:
         pass
 
-    async def handle_request(self, request):
+    async def handle_request(self, request: Request) -> None:
+        assert isinstance(request, SynapseRequest)
         respond_with_json(request, 200, {"some_key": "some_value_async"})
 
 
 class _SyncTestCustomEndpoint:
-    def __init__(self, config, module_api):
+    def __init__(self, config: JsonDict, module_api: Any) -> None:
         pass
 
-    async def handle_request(self, request):
+    async def handle_request(self, request: Request) -> None:
+        assert isinstance(request, SynapseRequest)
         respond_with_json(request, 200, {"some_key": "some_value_sync"})
 
 
@@ -41,7 +47,7 @@ class AdditionalResourceTests(HomeserverTestCase):
     and async handlers.
     """
 
-    def test_async(self):
+    def test_async(self) -> None:
         handler = _AsyncTestCustomEndpoint({}, None).handle_request
         resource = AdditionalResource(self.hs, handler)
 
@@ -52,7 +58,7 @@ class AdditionalResourceTests(HomeserverTestCase):
         self.assertEqual(channel.code, 200)
         self.assertEqual(channel.json_body, {"some_key": "some_value_async"})
 
-    def test_sync(self):
+    def test_sync(self) -> None:
         handler = _SyncTestCustomEndpoint({}, None).handle_request
         resource = AdditionalResource(self.hs, handler)
 
diff --git a/tests/http/test_client.py b/tests/http/test_client.py
index 7e2f2a01c..9cfe1ad0d 100644
--- a/tests/http/test_client.py
+++ b/tests/http/test_client.py
@@ -13,10 +13,12 @@
 #  limitations under the License.
 
 from io import BytesIO
+from typing import Tuple, Union
 from unittest.mock import Mock
 
 from netaddr import IPSet
 
+from twisted.internet.defer import Deferred
 from twisted.internet.error import DNSLookupError
 from twisted.python.failure import Failure
 from twisted.test.proto_helpers import AccumulatingProtocol
@@ -28,6 +30,7 @@ from synapse.http.client import (
     BlacklistingAgentWrapper,
     BlacklistingReactorWrapper,
     BodyExceededMaxSize,
+    _DiscardBodyWithMaxSizeProtocol,
     read_body_with_max_size,
 )
 
@@ -36,7 +39,9 @@ from tests.unittest import TestCase
 
 
 class ReadBodyWithMaxSizeTests(TestCase):
-    def _build_response(self, length=UNKNOWN_LENGTH):
+    def _build_response(
+        self, length: Union[int, str] = UNKNOWN_LENGTH
+    ) -> Tuple[BytesIO, "Deferred[int]", _DiscardBodyWithMaxSizeProtocol]:
         """Start reading the body, returns the response, result and proto"""
         response = Mock(length=length)
         result = BytesIO()
@@ -48,23 +53,27 @@ class ReadBodyWithMaxSizeTests(TestCase):
 
         return result, deferred, protocol
 
-    def _assert_error(self, deferred, protocol):
+    def _assert_error(
+        self, deferred: "Deferred[int]", protocol: _DiscardBodyWithMaxSizeProtocol
+    ) -> None:
         """Ensure that the expected error is received."""
-        self.assertIsInstance(deferred.result, Failure)
+        assert isinstance(deferred.result, Failure)
         self.assertIsInstance(deferred.result.value, BodyExceededMaxSize)
-        protocol.transport.abortConnection.assert_called_once()
+        assert protocol.transport is not None
+        # type-ignore: presumably abortConnection has been replaced with a Mock.
+        protocol.transport.abortConnection.assert_called_once()  # type: ignore[attr-defined]
 
-    def _cleanup_error(self, deferred):
+    def _cleanup_error(self, deferred: "Deferred[int]") -> None:
         """Ensure that the error in the Deferred is handled gracefully."""
         called = [False]
 
-        def errback(f):
+        def errback(f: Failure) -> None:
             called[0] = True
 
         deferred.addErrback(errback)
         self.assertTrue(called[0])
 
-    def test_no_error(self):
+    def test_no_error(self) -> None:
         """A response that is NOT too large."""
         result, deferred, protocol = self._build_response()
 
@@ -76,7 +85,7 @@ class ReadBodyWithMaxSizeTests(TestCase):
         self.assertEqual(result.getvalue(), b"12345")
         self.assertEqual(deferred.result, 5)
 
-    def test_too_large(self):
+    def test_too_large(self) -> None:
         """A response which is too large raises an exception."""
         result, deferred, protocol = self._build_response()
 
@@ -87,7 +96,7 @@ class ReadBodyWithMaxSizeTests(TestCase):
         self._assert_error(deferred, protocol)
         self._cleanup_error(deferred)
 
-    def test_multiple_packets(self):
+    def test_multiple_packets(self) -> None:
         """Data should be accumulated through mutliple packets."""
         result, deferred, protocol = self._build_response()
 
@@ -100,7 +109,7 @@ class ReadBodyWithMaxSizeTests(TestCase):
         self.assertEqual(result.getvalue(), b"1234")
         self.assertEqual(deferred.result, 4)
 
-    def test_additional_data(self):
+    def test_additional_data(self) -> None:
         """A connection can receive data after being closed."""
         result, deferred, protocol = self._build_response()
 
@@ -115,7 +124,7 @@ class ReadBodyWithMaxSizeTests(TestCase):
         self._assert_error(deferred, protocol)
         self._cleanup_error(deferred)
 
-    def test_content_length(self):
+    def test_content_length(self) -> None:
         """The body shouldn't be read (at all) if the Content-Length header is too large."""
         result, deferred, protocol = self._build_response(length=10)
 
@@ -132,7 +141,7 @@ class ReadBodyWithMaxSizeTests(TestCase):
 
 
 class BlacklistingAgentTest(TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
         self.reactor, self.clock = get_clock()
 
         self.safe_domain, self.safe_ip = b"safe.test", b"1.2.3.4"
@@ -151,7 +160,7 @@ class BlacklistingAgentTest(TestCase):
         self.ip_whitelist = IPSet([self.allowed_ip.decode()])
         self.ip_blacklist = IPSet(["5.0.0.0/8"])
 
-    def test_reactor(self):
+    def test_reactor(self) -> None:
         """Apply the blacklisting reactor and ensure it properly blocks connections to particular domains and IPs."""
         agent = Agent(
             BlacklistingReactorWrapper(
@@ -197,7 +206,7 @@ class BlacklistingAgentTest(TestCase):
             response = self.successResultOf(d)
             self.assertEqual(response.code, 200)
 
-    def test_agent(self):
+    def test_agent(self) -> None:
         """Apply the blacklisting agent and ensure it properly blocks connections to particular IPs."""
         agent = BlacklistingAgentWrapper(
             Agent(self.reactor),
diff --git a/tests/http/test_endpoint.py b/tests/http/test_endpoint.py
index a801f002a..8c18e5688 100644
--- a/tests/http/test_endpoint.py
+++ b/tests/http/test_endpoint.py
@@ -17,7 +17,7 @@ from tests import unittest
 
 
 class ServerNameTestCase(unittest.TestCase):
-    def test_parse_server_name(self):
+    def test_parse_server_name(self) -> None:
         test_data = {
             "localhost": ("localhost", None),
             "my-example.com:1234": ("my-example.com", 1234),
@@ -32,7 +32,7 @@ class ServerNameTestCase(unittest.TestCase):
         for i, o in test_data.items():
             self.assertEqual(parse_server_name(i), o)
 
-    def test_validate_bad_server_names(self):
+    def test_validate_bad_server_names(self) -> None:
         test_data = [
             "",  # empty
             "localhost:http",  # non-numeric port
diff --git a/tests/http/test_matrixfederationclient.py b/tests/http/test_matrixfederationclient.py
index be9eaf34e..fdd22a8e9 100644
--- a/tests/http/test_matrixfederationclient.py
+++ b/tests/http/test_matrixfederationclient.py
@@ -11,16 +11,16 @@
 # 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 Generator
 from unittest.mock import Mock
 
 from netaddr import IPSet
 from parameterized import parameterized
 
 from twisted.internet import defer
-from twisted.internet.defer import TimeoutError
+from twisted.internet.defer import Deferred, TimeoutError
 from twisted.internet.error import ConnectingCancelledError, DNSLookupError
-from twisted.test.proto_helpers import StringTransport
+from twisted.test.proto_helpers import MemoryReactor, StringTransport
 from twisted.web.client import ResponseNeverReceived
 from twisted.web.http import HTTPChannel
 
@@ -30,34 +30,43 @@ from synapse.http.matrixfederationclient import (
     MatrixFederationHttpClient,
     MatrixFederationRequest,
 )
-from synapse.logging.context import SENTINEL_CONTEXT, LoggingContext, current_context
+from synapse.logging.context import (
+    SENTINEL_CONTEXT,
+    LoggingContext,
+    LoggingContextOrSentinel,
+    current_context,
+)
+from synapse.server import HomeServer
+from synapse.util import Clock
 
 from tests.server import FakeTransport
 from tests.unittest import HomeserverTestCase
 
 
-def check_logcontext(context):
+def check_logcontext(context: LoggingContextOrSentinel) -> None:
     current = current_context()
     if current is not context:
         raise AssertionError("Expected logcontext %s but was %s" % (context, current))
 
 
 class FederationClientTests(HomeserverTestCase):
-    def make_homeserver(self, reactor, clock):
+    def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
         hs = self.setup_test_homeserver(reactor=reactor, clock=clock)
         return hs
 
-    def prepare(self, reactor, clock, homeserver):
+    def prepare(
+        self, reactor: MemoryReactor, clock: Clock, homeserver: HomeServer
+    ) -> None:
         self.cl = MatrixFederationHttpClient(self.hs, None)
         self.reactor.lookups["testserv"] = "1.2.3.4"
 
-    def test_client_get(self):
+    def test_client_get(self) -> None:
         """
         happy-path test of a GET request
         """
 
         @defer.inlineCallbacks
-        def do_request():
+        def do_request() -> Generator["Deferred[object]", object, object]:
             with LoggingContext("one") as context:
                 fetch_d = defer.ensureDeferred(
                     self.cl.get_json("testserv:8008", "foo/bar")
@@ -119,7 +128,7 @@ class FederationClientTests(HomeserverTestCase):
         # check the response is as expected
         self.assertEqual(res, {"a": 1})
 
-    def test_dns_error(self):
+    def test_dns_error(self) -> None:
         """
         If the DNS lookup returns an error, it will bubble up.
         """
@@ -132,7 +141,7 @@ class FederationClientTests(HomeserverTestCase):
         self.assertIsInstance(f.value, RequestSendFailed)
         self.assertIsInstance(f.value.inner_exception, DNSLookupError)
 
-    def test_client_connection_refused(self):
+    def test_client_connection_refused(self) -> None:
         d = defer.ensureDeferred(
             self.cl.get_json("testserv:8008", "foo/bar", timeout=10000)
         )
@@ -156,7 +165,7 @@ class FederationClientTests(HomeserverTestCase):
         self.assertIsInstance(f.value, RequestSendFailed)
         self.assertIs(f.value.inner_exception, e)
 
-    def test_client_never_connect(self):
+    def test_client_never_connect(self) -> None:
         """
         If the HTTP request is not connected and is timed out, it'll give a
         ConnectingCancelledError or TimeoutError.
@@ -188,7 +197,7 @@ class FederationClientTests(HomeserverTestCase):
             f.value.inner_exception, (ConnectingCancelledError, TimeoutError)
         )
 
-    def test_client_connect_no_response(self):
+    def test_client_connect_no_response(self) -> None:
         """
         If the HTTP request is connected, but gets no response before being
         timed out, it'll give a ResponseNeverReceived.
@@ -222,7 +231,7 @@ class FederationClientTests(HomeserverTestCase):
         self.assertIsInstance(f.value, RequestSendFailed)
         self.assertIsInstance(f.value.inner_exception, ResponseNeverReceived)
 
-    def test_client_ip_range_blacklist(self):
+    def test_client_ip_range_blacklist(self) -> None:
         """Ensure that Synapse does not try to connect to blacklisted IPs"""
 
         # Set up the ip_range blacklist
@@ -292,7 +301,7 @@ class FederationClientTests(HomeserverTestCase):
         f = self.failureResultOf(d, RequestSendFailed)
         self.assertIsInstance(f.value.inner_exception, ConnectingCancelledError)
 
-    def test_client_gets_headers(self):
+    def test_client_gets_headers(self) -> None:
         """
         Once the client gets the headers, _request returns successfully.
         """
@@ -319,7 +328,7 @@ class FederationClientTests(HomeserverTestCase):
         self.assertEqual(r.code, 200)
 
     @parameterized.expand(["get_json", "post_json", "delete_json", "put_json"])
-    def test_timeout_reading_body(self, method_name: str):
+    def test_timeout_reading_body(self, method_name: str) -> None:
         """
         If the HTTP request is connected, but gets no response before being
         timed out, it'll give a RequestSendFailed with can_retry.
@@ -351,7 +360,7 @@ class FederationClientTests(HomeserverTestCase):
         self.assertTrue(f.value.can_retry)
         self.assertIsInstance(f.value.inner_exception, defer.TimeoutError)
 
-    def test_client_requires_trailing_slashes(self):
+    def test_client_requires_trailing_slashes(self) -> None:
         """
         If a connection is made to a client but the client rejects it due to
         requiring a trailing slash. We need to retry the request with a
@@ -405,7 +414,7 @@ class FederationClientTests(HomeserverTestCase):
         r = self.successResultOf(d)
         self.assertEqual(r, {})
 
-    def test_client_does_not_retry_on_400_plus(self):
+    def test_client_does_not_retry_on_400_plus(self) -> None:
         """
         Another test for trailing slashes but now test that we don't retry on
         trailing slashes on a non-400/M_UNRECOGNIZED response.
@@ -450,7 +459,7 @@ class FederationClientTests(HomeserverTestCase):
         # We should get a 404 failure response
         self.failureResultOf(d)
 
-    def test_client_sends_body(self):
+    def test_client_sends_body(self) -> None:
         defer.ensureDeferred(
             self.cl.post_json(
                 "testserv:8008", "foo/bar", timeout=10000, data={"a": "b"}
@@ -474,7 +483,7 @@ class FederationClientTests(HomeserverTestCase):
         content = request.content.read()
         self.assertEqual(content, b'{"a":"b"}')
 
-    def test_closes_connection(self):
+    def test_closes_connection(self) -> None:
         """Check that the client closes unused HTTP connections"""
         d = defer.ensureDeferred(self.cl.get_json("testserv:8008", "foo/bar"))
 
@@ -514,7 +523,7 @@ class FederationClientTests(HomeserverTestCase):
         self.assertTrue(conn.disconnecting)
 
     @parameterized.expand([(b"",), (b"foo",), (b'{"a": Infinity}',)])
-    def test_json_error(self, return_value):
+    def test_json_error(self, return_value: bytes) -> None:
         """
         Test what happens if invalid JSON is returned from the remote endpoint.
         """
@@ -560,7 +569,7 @@ class FederationClientTests(HomeserverTestCase):
         f = self.failureResultOf(test_d)
         self.assertIsInstance(f.value, RequestSendFailed)
 
-    def test_too_big(self):
+    def test_too_big(self) -> None:
         """
         Test what happens if a huge response is returned from the remote endpoint.
         """
diff --git a/tests/http/test_proxyagent.py b/tests/http/test_proxyagent.py
index 2db77c6a7..a81794073 100644
--- a/tests/http/test_proxyagent.py
+++ b/tests/http/test_proxyagent.py
@@ -14,7 +14,7 @@
 import base64
 import logging
 import os
-from typing import Iterable, Optional
+from typing import List, Optional
 from unittest.mock import patch
 
 import treq
@@ -22,7 +22,11 @@ from netaddr import IPSet
 from parameterized import parameterized
 
 from twisted.internet import interfaces  # noqa: F401
-from twisted.internet.endpoints import HostnameEndpoint, _WrapperEndpoint
+from twisted.internet.endpoints import (
+    HostnameEndpoint,
+    _WrapperEndpoint,
+    _WrappingProtocol,
+)
 from twisted.internet.interfaces import IProtocol, IProtocolFactory
 from twisted.internet.protocol import Factory
 from twisted.protocols.tls import TLSMemoryBIOFactory, TLSMemoryBIOProtocol
@@ -32,7 +36,11 @@ from synapse.http.client import BlacklistingReactorWrapper
 from synapse.http.connectproxyclient import ProxyCredentials
 from synapse.http.proxyagent import ProxyAgent, parse_proxy
 
-from tests.http import TestServerTLSConnectionFactory, get_test_https_policy
+from tests.http import (
+    TestServerTLSConnectionFactory,
+    dummy_address,
+    get_test_https_policy,
+)
 from tests.server import FakeTransport, ThreadedMemoryReactorClock
 from tests.unittest import TestCase
 
@@ -183,7 +191,7 @@ class ProxyParserTests(TestCase):
         expected_hostname: bytes,
         expected_port: int,
         expected_credentials: Optional[bytes],
-    ):
+    ) -> None:
         """
         Tests that a given proxy URL will be broken into the components.
         Args:
@@ -209,7 +217,7 @@ class ProxyParserTests(TestCase):
 
 
 class MatrixFederationAgentTests(TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
         self.reactor = ThreadedMemoryReactorClock()
 
     def _make_connection(
@@ -218,7 +226,7 @@ class MatrixFederationAgentTests(TestCase):
         server_factory: IProtocolFactory,
         ssl: bool = False,
         expected_sni: Optional[bytes] = None,
-        tls_sanlist: Optional[Iterable[bytes]] = None,
+        tls_sanlist: Optional[List[bytes]] = None,
     ) -> IProtocol:
         """Builds a test server, and completes the outgoing client connection
 
@@ -244,7 +252,8 @@ class MatrixFederationAgentTests(TestCase):
         if ssl:
             server_factory = _wrap_server_factory_for_tls(server_factory, tls_sanlist)
 
-        server_protocol = server_factory.buildProtocol(None)
+        server_protocol = server_factory.buildProtocol(dummy_address)
+        assert server_protocol is not None
 
         # now, tell the client protocol factory to build the client protocol,
         # and wire the output of said protocol up to the server via
@@ -252,7 +261,8 @@ class MatrixFederationAgentTests(TestCase):
         #
         # Normally this would be done by the TCP socket code in Twisted, but we are
         # stubbing that out here.
-        client_protocol = client_factory.buildProtocol(None)
+        client_protocol = client_factory.buildProtocol(dummy_address)
+        assert client_protocol is not None
         client_protocol.makeConnection(
             FakeTransport(server_protocol, self.reactor, client_protocol)
         )
@@ -263,6 +273,7 @@ class MatrixFederationAgentTests(TestCase):
         )
 
         if ssl:
+            assert isinstance(server_protocol, TLSMemoryBIOProtocol)
             http_protocol = server_protocol.wrappedProtocol
             tls_connection = server_protocol._tlsConnection
         else:
@@ -288,7 +299,7 @@ class MatrixFederationAgentTests(TestCase):
         scheme: bytes,
         hostname: bytes,
         path: bytes,
-    ):
+    ) -> None:
         """Runs a test case for a direct connection not going through a proxy.
 
         Args:
@@ -319,6 +330,7 @@ class MatrixFederationAgentTests(TestCase):
             ssl=is_https,
             expected_sni=hostname if is_https else None,
         )
+        assert isinstance(http_server, HTTPChannel)
 
         # the FakeTransport is async, so we need to pump the reactor
         self.reactor.advance(0)
@@ -339,34 +351,34 @@ class MatrixFederationAgentTests(TestCase):
         body = self.successResultOf(treq.content(resp))
         self.assertEqual(body, b"result")
 
-    def test_http_request(self):
+    def test_http_request(self) -> None:
         agent = ProxyAgent(self.reactor)
         self._test_request_direct_connection(agent, b"http", b"test.com", b"")
 
-    def test_https_request(self):
+    def test_https_request(self) -> None:
         agent = ProxyAgent(self.reactor, contextFactory=get_test_https_policy())
         self._test_request_direct_connection(agent, b"https", b"test.com", b"abc")
 
-    def test_http_request_use_proxy_empty_environment(self):
+    def test_http_request_use_proxy_empty_environment(self) -> None:
         agent = ProxyAgent(self.reactor, use_proxy=True)
         self._test_request_direct_connection(agent, b"http", b"test.com", b"")
 
     @patch.dict(os.environ, {"http_proxy": "proxy.com:8888", "NO_PROXY": "test.com"})
-    def test_http_request_via_uppercase_no_proxy(self):
+    def test_http_request_via_uppercase_no_proxy(self) -> None:
         agent = ProxyAgent(self.reactor, use_proxy=True)
         self._test_request_direct_connection(agent, b"http", b"test.com", b"")
 
     @patch.dict(
         os.environ, {"http_proxy": "proxy.com:8888", "no_proxy": "test.com,unused.com"}
     )
-    def test_http_request_via_no_proxy(self):
+    def test_http_request_via_no_proxy(self) -> None:
         agent = ProxyAgent(self.reactor, use_proxy=True)
         self._test_request_direct_connection(agent, b"http", b"test.com", b"")
 
     @patch.dict(
         os.environ, {"https_proxy": "proxy.com", "no_proxy": "test.com,unused.com"}
     )
-    def test_https_request_via_no_proxy(self):
+    def test_https_request_via_no_proxy(self) -> None:
         agent = ProxyAgent(
             self.reactor,
             contextFactory=get_test_https_policy(),
@@ -375,12 +387,12 @@ class MatrixFederationAgentTests(TestCase):
         self._test_request_direct_connection(agent, b"https", b"test.com", b"abc")
 
     @patch.dict(os.environ, {"http_proxy": "proxy.com:8888", "no_proxy": "*"})
-    def test_http_request_via_no_proxy_star(self):
+    def test_http_request_via_no_proxy_star(self) -> None:
         agent = ProxyAgent(self.reactor, use_proxy=True)
         self._test_request_direct_connection(agent, b"http", b"test.com", b"")
 
     @patch.dict(os.environ, {"https_proxy": "proxy.com", "no_proxy": "*"})
-    def test_https_request_via_no_proxy_star(self):
+    def test_https_request_via_no_proxy_star(self) -> None:
         agent = ProxyAgent(
             self.reactor,
             contextFactory=get_test_https_policy(),
@@ -389,7 +401,7 @@ class MatrixFederationAgentTests(TestCase):
         self._test_request_direct_connection(agent, b"https", b"test.com", b"abc")
 
     @patch.dict(os.environ, {"http_proxy": "proxy.com:8888", "no_proxy": "unused.com"})
-    def test_http_request_via_proxy(self):
+    def test_http_request_via_proxy(self) -> None:
         """
         Tests that requests can be made through a proxy.
         """
@@ -401,7 +413,7 @@ class MatrixFederationAgentTests(TestCase):
         os.environ,
         {"http_proxy": "bob:pinkponies@proxy.com:8888", "no_proxy": "unused.com"},
     )
-    def test_http_request_via_proxy_with_auth(self):
+    def test_http_request_via_proxy_with_auth(self) -> None:
         """
         Tests that authenticated requests can be made through a proxy.
         """
@@ -412,7 +424,7 @@ class MatrixFederationAgentTests(TestCase):
     @patch.dict(
         os.environ, {"http_proxy": "https://proxy.com:8888", "no_proxy": "unused.com"}
     )
-    def test_http_request_via_https_proxy(self):
+    def test_http_request_via_https_proxy(self) -> None:
         self._do_http_request_via_proxy(
             expect_proxy_ssl=True, expected_auth_credentials=None
         )
@@ -424,13 +436,13 @@ class MatrixFederationAgentTests(TestCase):
             "no_proxy": "unused.com",
         },
     )
-    def test_http_request_via_https_proxy_with_auth(self):
+    def test_http_request_via_https_proxy_with_auth(self) -> None:
         self._do_http_request_via_proxy(
             expect_proxy_ssl=True, expected_auth_credentials=b"bob:pinkponies"
         )
 
     @patch.dict(os.environ, {"https_proxy": "proxy.com", "no_proxy": "unused.com"})
-    def test_https_request_via_proxy(self):
+    def test_https_request_via_proxy(self) -> None:
         """Tests that TLS-encrypted requests can be made through a proxy"""
         self._do_https_request_via_proxy(
             expect_proxy_ssl=False, expected_auth_credentials=None
@@ -440,7 +452,7 @@ class MatrixFederationAgentTests(TestCase):
         os.environ,
         {"https_proxy": "bob:pinkponies@proxy.com", "no_proxy": "unused.com"},
     )
-    def test_https_request_via_proxy_with_auth(self):
+    def test_https_request_via_proxy_with_auth(self) -> None:
         """Tests that authenticated, TLS-encrypted requests can be made through a proxy"""
         self._do_https_request_via_proxy(
             expect_proxy_ssl=False, expected_auth_credentials=b"bob:pinkponies"
@@ -449,7 +461,7 @@ class MatrixFederationAgentTests(TestCase):
     @patch.dict(
         os.environ, {"https_proxy": "https://proxy.com", "no_proxy": "unused.com"}
     )
-    def test_https_request_via_https_proxy(self):
+    def test_https_request_via_https_proxy(self) -> None:
         """Tests that TLS-encrypted requests can be made through a proxy"""
         self._do_https_request_via_proxy(
             expect_proxy_ssl=True, expected_auth_credentials=None
@@ -459,7 +471,7 @@ class MatrixFederationAgentTests(TestCase):
         os.environ,
         {"https_proxy": "https://bob:pinkponies@proxy.com", "no_proxy": "unused.com"},
     )
-    def test_https_request_via_https_proxy_with_auth(self):
+    def test_https_request_via_https_proxy_with_auth(self) -> None:
         """Tests that authenticated, TLS-encrypted requests can be made through a proxy"""
         self._do_https_request_via_proxy(
             expect_proxy_ssl=True, expected_auth_credentials=b"bob:pinkponies"
@@ -469,7 +481,7 @@ class MatrixFederationAgentTests(TestCase):
         self,
         expect_proxy_ssl: bool = False,
         expected_auth_credentials: Optional[bytes] = None,
-    ):
+    ) -> None:
         """Send a http request via an agent and check that it is correctly received at
             the proxy. The proxy can use either http or https.
         Args:
@@ -501,6 +513,7 @@ class MatrixFederationAgentTests(TestCase):
             tls_sanlist=[b"DNS:proxy.com"] if expect_proxy_ssl else None,
             expected_sni=b"proxy.com" if expect_proxy_ssl else None,
         )
+        assert isinstance(http_server, HTTPChannel)
 
         # the FakeTransport is async, so we need to pump the reactor
         self.reactor.advance(0)
@@ -542,7 +555,7 @@ class MatrixFederationAgentTests(TestCase):
         self,
         expect_proxy_ssl: bool = False,
         expected_auth_credentials: Optional[bytes] = None,
-    ):
+    ) -> None:
         """Send a https request via an agent and check that it is correctly received at
             the proxy and client. The proxy can use either http or https.
         Args:
@@ -606,10 +619,12 @@ class MatrixFederationAgentTests(TestCase):
         # now we make another test server to act as the upstream HTTP server.
         server_ssl_protocol = _wrap_server_factory_for_tls(
             _get_test_protocol_factory()
-        ).buildProtocol(None)
+        ).buildProtocol(dummy_address)
+        assert isinstance(server_ssl_protocol, TLSMemoryBIOProtocol)
 
         # Tell the HTTP server to send outgoing traffic back via the proxy's transport.
         proxy_server_transport = proxy_server.transport
+        assert proxy_server_transport is not None
         server_ssl_protocol.makeConnection(proxy_server_transport)
 
         # ... and replace the protocol on the proxy's transport with the
@@ -644,6 +659,7 @@ class MatrixFederationAgentTests(TestCase):
 
         # now there should be a pending request
         http_server = server_ssl_protocol.wrappedProtocol
+        assert isinstance(http_server, HTTPChannel)
         self.assertEqual(len(http_server.requests), 1)
 
         request = http_server.requests[0]
@@ -667,7 +683,7 @@ class MatrixFederationAgentTests(TestCase):
         self.assertEqual(body, b"result")
 
     @patch.dict(os.environ, {"http_proxy": "proxy.com:8888"})
-    def test_http_request_via_proxy_with_blacklist(self):
+    def test_http_request_via_proxy_with_blacklist(self) -> None:
         # The blacklist includes the configured proxy IP.
         agent = ProxyAgent(
             BlacklistingReactorWrapper(
@@ -691,6 +707,7 @@ class MatrixFederationAgentTests(TestCase):
         http_server = self._make_connection(
             client_factory, _get_test_protocol_factory()
         )
+        assert isinstance(http_server, HTTPChannel)
 
         # the FakeTransport is async, so we need to pump the reactor
         self.reactor.advance(0)
@@ -712,7 +729,7 @@ class MatrixFederationAgentTests(TestCase):
         self.assertEqual(body, b"result")
 
     @patch.dict(os.environ, {"HTTPS_PROXY": "proxy.com"})
-    def test_https_request_via_uppercase_proxy_with_blacklist(self):
+    def test_https_request_via_uppercase_proxy_with_blacklist(self) -> None:
         # The blacklist includes the configured proxy IP.
         agent = ProxyAgent(
             BlacklistingReactorWrapper(
@@ -737,11 +754,15 @@ class MatrixFederationAgentTests(TestCase):
         proxy_server = self._make_connection(
             client_factory, _get_test_protocol_factory()
         )
+        assert isinstance(proxy_server, HTTPChannel)
 
         # fish the transports back out so that we can do the old switcheroo
         s2c_transport = proxy_server.transport
+        assert isinstance(s2c_transport, FakeTransport)
         client_protocol = s2c_transport.other
+        assert isinstance(client_protocol, _WrappingProtocol)
         c2s_transport = client_protocol.transport
+        assert isinstance(c2s_transport, FakeTransport)
 
         # the FakeTransport is async, so we need to pump the reactor
         self.reactor.advance(0)
@@ -762,8 +783,10 @@ class MatrixFederationAgentTests(TestCase):
 
         # now we can replace the proxy channel with a new, SSL-wrapped HTTP channel
         ssl_factory = _wrap_server_factory_for_tls(_get_test_protocol_factory())
-        ssl_protocol = ssl_factory.buildProtocol(None)
+        ssl_protocol = ssl_factory.buildProtocol(dummy_address)
+        assert isinstance(ssl_protocol, TLSMemoryBIOProtocol)
         http_server = ssl_protocol.wrappedProtocol
+        assert isinstance(http_server, HTTPChannel)
 
         ssl_protocol.makeConnection(
             FakeTransport(client_protocol, self.reactor, ssl_protocol)
@@ -797,28 +820,28 @@ class MatrixFederationAgentTests(TestCase):
         self.assertEqual(body, b"result")
 
     @patch.dict(os.environ, {"http_proxy": "proxy.com:8888"})
-    def test_proxy_with_no_scheme(self):
+    def test_proxy_with_no_scheme(self) -> None:
         http_proxy_agent = ProxyAgent(self.reactor, use_proxy=True)
-        self.assertIsInstance(http_proxy_agent.http_proxy_endpoint, HostnameEndpoint)
+        assert isinstance(http_proxy_agent.http_proxy_endpoint, HostnameEndpoint)
         self.assertEqual(http_proxy_agent.http_proxy_endpoint._hostStr, "proxy.com")
         self.assertEqual(http_proxy_agent.http_proxy_endpoint._port, 8888)
 
     @patch.dict(os.environ, {"http_proxy": "socks://proxy.com:8888"})
-    def test_proxy_with_unsupported_scheme(self):
+    def test_proxy_with_unsupported_scheme(self) -> None:
         with self.assertRaises(ValueError):
             ProxyAgent(self.reactor, use_proxy=True)
 
     @patch.dict(os.environ, {"http_proxy": "http://proxy.com:8888"})
-    def test_proxy_with_http_scheme(self):
+    def test_proxy_with_http_scheme(self) -> None:
         http_proxy_agent = ProxyAgent(self.reactor, use_proxy=True)
-        self.assertIsInstance(http_proxy_agent.http_proxy_endpoint, HostnameEndpoint)
+        assert isinstance(http_proxy_agent.http_proxy_endpoint, HostnameEndpoint)
         self.assertEqual(http_proxy_agent.http_proxy_endpoint._hostStr, "proxy.com")
         self.assertEqual(http_proxy_agent.http_proxy_endpoint._port, 8888)
 
     @patch.dict(os.environ, {"http_proxy": "https://proxy.com:8888"})
-    def test_proxy_with_https_scheme(self):
+    def test_proxy_with_https_scheme(self) -> None:
         https_proxy_agent = ProxyAgent(self.reactor, use_proxy=True)
-        self.assertIsInstance(https_proxy_agent.http_proxy_endpoint, _WrapperEndpoint)
+        assert isinstance(https_proxy_agent.http_proxy_endpoint, _WrapperEndpoint)
         self.assertEqual(
             https_proxy_agent.http_proxy_endpoint._wrappedEndpoint._hostStr, "proxy.com"
         )
@@ -828,7 +851,7 @@ class MatrixFederationAgentTests(TestCase):
 
 
 def _wrap_server_factory_for_tls(
-    factory: IProtocolFactory, sanlist: Iterable[bytes] = None
+    factory: IProtocolFactory, sanlist: Optional[List[bytes]] = None
 ) -> IProtocolFactory:
     """Wrap an existing Protocol Factory with a test TLSMemoryBIOFactory
 
@@ -865,6 +888,6 @@ def _get_test_protocol_factory() -> IProtocolFactory:
     return server_factory
 
 
-def _log_request(request: str):
+def _log_request(request: str) -> None:
     """Implements Factory.log, which is expected by Request.finish"""
     logger.info(f"Completed request {request}")
diff --git a/tests/http/test_servlet.py b/tests/http/test_servlet.py
index 46166292f..c8d215b6d 100644
--- a/tests/http/test_servlet.py
+++ b/tests/http/test_servlet.py
@@ -14,7 +14,7 @@
 import json
 from http import HTTPStatus
 from io import BytesIO
-from typing import Tuple
+from typing import Tuple, Union
 from unittest.mock import Mock
 
 from synapse.api.errors import Codes, SynapseError
@@ -33,7 +33,7 @@ from tests import unittest
 from tests.http.server._base import test_disconnect
 
 
-def make_request(content):
+def make_request(content: Union[bytes, JsonDict]) -> Mock:
     """Make an object that acts enough like a request."""
     request = Mock(spec=["method", "uri", "content"])
 
@@ -47,7 +47,7 @@ def make_request(content):
 
 
 class TestServletUtils(unittest.TestCase):
-    def test_parse_json_value(self):
+    def test_parse_json_value(self) -> None:
         """Basic tests for parse_json_value_from_request."""
         # Test round-tripping.
         obj = {"foo": 1}
@@ -78,7 +78,7 @@ class TestServletUtils(unittest.TestCase):
         with self.assertRaises(SynapseError):
             parse_json_value_from_request(make_request(b'{"foo": Infinity}'))
 
-    def test_parse_json_object(self):
+    def test_parse_json_object(self) -> None:
         """Basic tests for parse_json_object_from_request."""
         # Test empty.
         result = parse_json_object_from_request(
diff --git a/tests/http/test_simple_client.py b/tests/http/test_simple_client.py
index c85a3665c..010601da4 100644
--- a/tests/http/test_simple_client.py
+++ b/tests/http/test_simple_client.py
@@ -17,22 +17,24 @@ from netaddr import IPSet
 
 from twisted.internet import defer
 from twisted.internet.error import DNSLookupError
+from twisted.test.proto_helpers import MemoryReactor
 
 from synapse.http import RequestTimedOutError
 from synapse.http.client import SimpleHttpClient
 from synapse.server import HomeServer
+from synapse.util import Clock
 
 from tests.unittest import HomeserverTestCase
 
 
 class SimpleHttpClientTests(HomeserverTestCase):
-    def prepare(self, reactor, clock, hs: "HomeServer"):
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: "HomeServer") -> None:
         # Add a DNS entry for a test server
         self.reactor.lookups["testserv"] = "1.2.3.4"
 
         self.cl = hs.get_simple_http_client()
 
-    def test_dns_error(self):
+    def test_dns_error(self) -> None:
         """
         If the DNS lookup returns an error, it will bubble up.
         """
@@ -42,7 +44,7 @@ class SimpleHttpClientTests(HomeserverTestCase):
         f = self.failureResultOf(d)
         self.assertIsInstance(f.value, DNSLookupError)
 
-    def test_client_connection_refused(self):
+    def test_client_connection_refused(self) -> None:
         d = defer.ensureDeferred(self.cl.get_json("http://testserv:8008/foo/bar"))
 
         self.pump()
@@ -63,7 +65,7 @@ class SimpleHttpClientTests(HomeserverTestCase):
 
         self.assertIs(f.value, e)
 
-    def test_client_never_connect(self):
+    def test_client_never_connect(self) -> None:
         """
         If the HTTP request is not connected and is timed out, it'll give a
         ConnectingCancelledError or TimeoutError.
@@ -90,7 +92,7 @@ class SimpleHttpClientTests(HomeserverTestCase):
 
         self.assertIsInstance(f.value, RequestTimedOutError)
 
-    def test_client_connect_no_response(self):
+    def test_client_connect_no_response(self) -> None:
         """
         If the HTTP request is connected, but gets no response before being
         timed out, it'll give a ResponseNeverReceived.
@@ -121,7 +123,7 @@ class SimpleHttpClientTests(HomeserverTestCase):
 
         self.assertIsInstance(f.value, RequestTimedOutError)
 
-    def test_client_ip_range_blacklist(self):
+    def test_client_ip_range_blacklist(self) -> None:
         """Ensure that Synapse does not try to connect to blacklisted IPs"""
 
         # Add some DNS entries we'll blacklist
diff --git a/tests/http/test_site.py b/tests/http/test_site.py
index b2dbf76d3..9a78fede9 100644
--- a/tests/http/test_site.py
+++ b/tests/http/test_site.py
@@ -13,18 +13,20 @@
 # limitations under the License.
 
 from twisted.internet.address import IPv6Address
-from twisted.test.proto_helpers import StringTransport
+from twisted.test.proto_helpers import MemoryReactor, StringTransport
 
 from synapse.app.homeserver import SynapseHomeServer
+from synapse.server import HomeServer
+from synapse.util import Clock
 
 from tests.unittest import HomeserverTestCase
 
 
 class SynapseRequestTestCase(HomeserverTestCase):
-    def make_homeserver(self, reactor, clock):
+    def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
         return self.setup_test_homeserver(homeserver_to_use=SynapseHomeServer)
 
-    def test_large_request(self):
+    def test_large_request(self) -> None:
         """overlarge HTTP requests should be rejected"""
         self.hs.start_listening()
 
diff --git a/tests/server.py b/tests/server.py
index b1730fcc8..237bcad8b 100644
--- a/tests/server.py
+++ b/tests/server.py
@@ -70,7 +70,7 @@ from synapse.logging.context import ContextResourceUsage
 from synapse.server import HomeServer
 from synapse.storage import DataStore
 from synapse.storage.engines import PostgresEngine, create_engine
-from synapse.types import JsonDict
+from synapse.types import ISynapseReactor, JsonDict
 from synapse.util import Clock
 
 from tests.utils import (
@@ -401,7 +401,9 @@ def make_request(
     return channel
 
 
-@implementer(IReactorPluggableNameResolver)
+# ISynapseReactor implies IReactorPluggableNameResolver, but explicitly
+# marking this as an implementer of the latter seems to keep mypy-zope happier.
+@implementer(IReactorPluggableNameResolver, ISynapseReactor)
 class ThreadedMemoryReactorClock(MemoryReactorClock):
     """
     A MemoryReactorClock that supports callFromThread.