diff --git a/synapse/config/_base.py b/synapse/config/_base.py
index 5613f38e4..a219a8355 100644
--- a/synapse/config/_base.py
+++ b/synapse/config/_base.py
@@ -405,7 +405,10 @@ class Config(object):
             self.invoke_all("generate_files", config)
             return
 
-        self.invoke_all("read_config", config)
+        self.parse_config_dict(config)
+
+    def parse_config_dict(self, config_dict):
+        self.invoke_all("read_config", config_dict)
 
 
 def find_config_files(search_paths):
diff --git a/synapse/config/key.py b/synapse/config/key.py
index 2bd5531ac..933928885 100644
--- a/synapse/config/key.py
+++ b/synapse/config/key.py
@@ -38,7 +38,12 @@ logger = logging.getLogger(__name__)
 class KeyConfig(Config):
 
     def read_config(self, config):
-        self.signing_key = self.read_signing_key(config["signing_key_path"])
+        # the signing key can be specified inline or in a separate file
+        if "signing_key" in config:
+            self.signing_key = read_signing_keys([config["signing_key"]])
+        else:
+            self.signing_key = self.read_signing_key(config["signing_key_path"])
+
         self.old_signing_keys = self.read_old_signing_keys(
             config.get("old_signing_keys", {})
         )
diff --git a/tests/utils.py b/tests/utils.py
index b58b674aa..eeb4bce5a 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -28,7 +28,7 @@ from twisted.internet import defer, reactor
 
 from synapse.api.constants import EventTypes, RoomVersions
 from synapse.api.errors import CodeMessageException, cs_error
-from synapse.config.server import ServerConfig
+from synapse.config.homeserver import HomeServerConfig
 from synapse.federation.transport import server as federation_server
 from synapse.http.server import HttpServer
 from synapse.server import HomeServer
@@ -111,14 +111,25 @@ def default_config(name):
     """
     Create a reasonable test config.
     """
-    config = Mock()
-    config.signing_key = [MockKey()]
+    config_dict = {
+        "server_name": name,
+        "media_store_path": "media",
+        "uploads_path": "uploads",
+
+        # the test signing key is just an arbitrary ed25519 key to keep the config
+        # parser happy
+        "signing_key": "ed25519 a_lPym qvioDNmfExFBRPgdTU+wtFYKq4JfwFRv7sYVgWvmgJg",
+    }
+
+    config = HomeServerConfig()
+    config.parse_config_dict(config_dict)
+
+    # TODO: move this stuff into config_dict or get rid of it
     config.event_cache_size = 1
     config.enable_registration = True
     config.enable_registration_captcha = False
     config.macaroon_secret_key = "not even a little secret"
     config.expire_access_token = False
-    config.server_name = name
     config.trusted_third_party_id_servers = []
     config.room_invite_state_types = []
     config.password_providers = []
@@ -176,13 +187,6 @@ def default_config(name):
     # background, which upsets the test runner.
     config.update_user_directory = False
 
-    def is_threepid_reserved(threepid):
-        return ServerConfig.is_threepid_reserved(
-            config.mau_limits_reserved_threepids, threepid
-        )
-
-    config.is_threepid_reserved.side_effect = is_threepid_reserved
-
     return config