Tidy validation signatures

lighthouse/state/validation/signatures.rs

@@ -18,7 +18,8 @@ pub enum SignatureVerificationError {
     DBError(String),
 }
 
-fn verify_aggregate_signature_for_indices<T>(message: &[u8],
+pub fn verify_aggregate_signature_for_indices<T>(
+    message: &[u8],
     agg_sig: &AggregateSignature,
     attestation_indices: &[usize],
     bitfield: &Bitfield,
@@ -68,6 +69,15 @@ mod tests {
     use super::super::db::MemoryDB;
     use std::sync::Arc;
 
+    /*
+     * Cases that still need testing:
+     *
+     * - No signatures.
+     * - Database failure.
+     * - Unknown validator index.
+     * - Extra validator on signature.
+     */
+
     #[test]
     fn test_signature_verification() {
         let message = "cats".as_bytes();