Add tests for empty localparts

src/room_alias_id.rs

@@ -138,6 +138,14 @@ mod tests {
         );
     }
 
+    #[test]
+    fn missing_localpart() {
+        assert_eq!(
+            RoomAliasId::try_from("#:example.com").unwrap_err(),
+            Error::InvalidLocalPart
+        );
+    }
+
     #[test]
     fn missing_room_alias_id_delimiter() {
         assert_eq!(

src/user_id.rs

@@ -297,6 +297,14 @@ mod tests {
         );
     }
 
+    #[test]
+    fn missing_localpart() {
+        assert_eq!(
+            UserId::try_from("@:example.com").unwrap_err(),
+            Error::InvalidLocalPart
+        );
+    }
+
     #[test]
     fn missing_user_id_delimiter() {
         assert_eq!(