diff --git a/zebra-chain/src/keys/sprout.rs b/zebra-chain/src/keys/sprout.rs
index fe2289a8..943a3297 100644
--- a/zebra-chain/src/keys/sprout.rs
+++ b/zebra-chain/src/keys/sprout.rs
@@ -99,6 +99,7 @@ mod tests {
     use super::*;
 
     #[test]
+    // TODO: test vectors, not just random data
     fn derive_keys() {
         let mut bytes = [0u8; 32];
         OsRng.fill_bytes(&mut bytes);