Add a separate json_list method on FakeChannel.

tests/rest/client/test_rooms.py

@@ -495,10 +495,8 @@ def test_get_state_cancellation(self) -> None:
         )
 
         self.assertEqual(HTTPStatus.OK, channel.code, msg=channel.result["body"])
-        # json_body is defined as JsonDict, but it can be any valid JSON.
-        json_body: List[JsonDict] = channel.json_body  # type: ignore[assignment]
         self.assertCountEqual(
-            [state_event["type"] for state_event in json_body],
+            [state_event["type"] for state_event in channel.json_list],
             {
                 "m.room.create",
                 "m.room.power_levels",

tests/server.py

@@ -25,6 +25,7 @@
     Callable,
     Dict,
     Iterable,
+    List,
     MutableMapping,
     Optional,
     Tuple,
@@ -121,7 +122,15 @@ def request(self, request: Request) -> None:
 
     @property
     def json_body(self) -> JsonDict:
-        return json.loads(self.text_body)
+        body = json.loads(self.text_body)
+        assert isinstance(body, dict)
+        return body
+
+    @property
+    def json_list(self) -> List[JsonDict]:
+        body = json.loads(self.text_body)
+        assert isinstance(body, list)
+        return body
 
     @property
     def text_body(self) -> str: