2 files changed, 37 insertions, 2 deletions
diff --git a/tests/handlers/test_oauth_delegation.py b/tests/handlers/test_oauth_delegation.py
index b79c43a424..16ce2c069d 100644
--- a/tests/handlers/test_oauth_delegation.py
+++ b/tests/handlers/test_oauth_delegation.py
@@ -30,6 +30,7 @@ from synapse.api.errors import (
     Codes,
     InvalidClientTokenError,
     OAuthInsufficientScopeError,
+    SynapseError,
 )
 from synapse.rest import admin
 from synapse.rest.client import account, devices, keys, login, logout, register
@@ -405,6 +406,40 @@ class MSC3861OAuthDelegation(HomeserverTestCase):
         )
         self.assertEqual(requester.device_id, DEVICE)
 
+    def test_unavailable_introspection_endpoint(self) -> None:
+        """The handler should return an internal server error."""
+        request = Mock(args={})
+        request.args[b"access_token"] = [b"mockAccessToken"]
+        request.requestHeaders.getRawHeaders = mock_getRawHeaders()
+
+        # The introspection endpoint is returning an error.
+        self.http_client.request = simple_async_mock(
+            return_value=FakeResponse(code=500, body=b"Internal Server Error")
+        )
+        error = self.get_failure(self.auth.get_user_by_req(request), SynapseError)
+        self.assertEqual(error.value.code, 503)
+
+        # The introspection endpoint request fails.
+        self.http_client.request = simple_async_mock(raises=Exception())
+        error = self.get_failure(self.auth.get_user_by_req(request), SynapseError)
+        self.assertEqual(error.value.code, 503)
+
+        # The introspection endpoint does not return a JSON object.
+        self.http_client.request = simple_async_mock(
+            return_value=FakeResponse.json(
+                code=200, payload=["this is an array", "not an object"]
+            )
+        )
+        error = self.get_failure(self.auth.get_user_by_req(request), SynapseError)
+        self.assertEqual(error.value.code, 503)
+
+        # The introspection endpoint does not return valid JSON.
+        self.http_client.request = simple_async_mock(
+            return_value=FakeResponse(code=200, body=b"this is not valid JSON")
+        )
+        error = self.get_failure(self.auth.get_user_by_req(request), SynapseError)
+        self.assertEqual(error.value.code, 503)
+
     def make_device_keys(self, user_id: str, device_id: str) -> JsonDict:
         # We only generate a master key to simplify the test.
         master_signing_key = generate_signing_key(device_id)
diff --git a/tests/test_utils/__init__.py b/tests/test_utils/__init__.py
index e5dae670a7..c8cc841d95 100644
--- a/tests/test_utils/__init__.py
+++ b/tests/test_utils/__init__.py
@@ -33,7 +33,7 @@ from twisted.web.http import RESPONSES
 from twisted.web.http_headers import Headers
 from twisted.web.iweb import IResponse
 
-from synapse.types import JsonDict
+from synapse.types import JsonSerializable
 
 if TYPE_CHECKING:
     from sys import UnraisableHookArgs
@@ -145,7 +145,7 @@ class FakeResponse:  # type: ignore[misc]
         protocol.connectionLost(Failure(ResponseDone()))
 
     @classmethod
-    def json(cls, *, code: int = 200, payload: JsonDict) -> "FakeResponse":
+    def json(cls, *, code: int = 200, payload: JsonSerializable) -> "FakeResponse":
         headers = Headers({"Content-Type": ["application/json"]})
         body = json.dumps(payload).encode("utf-8")
         return cls(code=code, body=body, headers=headers)