Add tests for unstable support whilst still relied on

tests/rest/client/test_login_token_request.py

@@ -15,7 +15,7 @@
 from twisted.test.proto_helpers import MemoryReactor
 
 from synapse.rest import admin
-from synapse.rest.client import login, login_token_request
+from synapse.rest.client import login, login_token_request, versions
 from synapse.server import HomeServer
 from synapse.util import Clock
 
@@ -30,6 +30,7 @@ class LoginTokenRequestServletTestCase(unittest.HomeserverTestCase):
         login.register_servlets,
         admin.register_servlets,
         login_token_request.register_servlets,
+        versions.register_servlets, # TODO: remove once unstable revision 0 support is removed
     ]
 
     def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
@@ -131,3 +132,28 @@ class LoginTokenRequestServletTestCase(unittest.HomeserverTestCase):
         channel = self.make_request("POST", GET_TOKEN_ENDPOINT, {}, access_token=token)
         self.assertEqual(channel.code, 200)
         self.assertEqual(channel.json_body["expires_in_ms"], 15000)
+
+    @override_config(
+        {
+            "login_via_existing_session": {
+                "enabled": True,
+                "require_ui_auth": False,
+                "token_timeout": "15s",
+            }
+        }
+    )
+    def test_unstable_support(self) -> None:
+        # TODO: remove support for unstable MSC3882 is no longer needed
+
+        # check feature is advertised in versions response:
+        channel = self.make_request("GET", "/_matrix/client/versions", {}, access_token=None)
+        self.assertEqual(channel.code, 200)
+        self.assertEqual(channel.json_body["unstable_features"]["org.matrix.msc3882"], True)
+
+        self.register_user(self.user, self.password)
+        token = self.login(self.user, self.password)
+
+        # check feature is available via the unstable endpoint and returns an expires_in value in seconds
+        channel = self.make_request("POST", "/_matrix/client/unstable/org.matrix.msc3882/login/token", {}, access_token=token)
+        self.assertEqual(channel.code, 200)
+        self.assertEqual(channel.json_body["expires_in"], 15)