Clean up the test code for client disconnections (#12929)

* Reword failure message about `await_result=False`
* Use `reactor.advance()` instead of `reactor.pump()`
* Raise `AssertionError`s ourselves
* Un-instance method `_test_disconnect`
* Replace `ThreadedMemoryReactorClock` with `MemoryReactorClock`

1 files changed, 4 insertions, 6 deletions

diff --git a/tests/http/test_servlet.py b/tests/http/test_servlet.py
index b3655d7b44..bb966c80c6 100644
--- a/tests/http/test_servlet.py
+++ b/tests/http/test_servlet.py
@@ -30,7 +30,7 @@ from synapse.server import HomeServer
 from synapse.types import JsonDict
 
 from tests import unittest
-from tests.http.server._base import EndpointCancellationTestHelperMixin
+from tests.http.server._base import test_disconnect
 
 
 def make_request(content):
@@ -108,9 +108,7 @@ class CancellableRestServlet(RestServlet):
         return HTTPStatus.OK, {"result": True}
 
 
-class TestRestServletCancellation(
-    unittest.HomeserverTestCase, EndpointCancellationTestHelperMixin
-):
+class TestRestServletCancellation(unittest.HomeserverTestCase):
     """Tests for `RestServlet` cancellation."""
 
     servlets = [
@@ -120,7 +118,7 @@ class TestRestServletCancellation(
     def test_cancellable_disconnect(self) -> None:
         """Test that handlers with the `@cancellable` flag can be cancelled."""
         channel = self.make_request("GET", "/sleep", await_result=False)
-        self._test_disconnect(
+        test_disconnect(
             self.reactor,
             channel,
             expect_cancellation=True,
@@ -130,7 +128,7 @@ class TestRestServletCancellation(
     def test_uncancellable_disconnect(self) -> None:
         """Test that handlers without the `@cancellable` flag cannot be cancelled."""
         channel = self.make_request("POST", "/sleep", await_result=False)
-        self._test_disconnect(
+        test_disconnect(
             self.reactor,
             channel,
             expect_cancellation=False,