Add test for attestation msg generation

lighthouse/state/attestation_record/validation/message_generation.rs

@@ -5,11 +5,12 @@ use super::utils::types::Hash256;
 /// Generates the message used to validate the signature provided with an AttestationRecord.
 ///
 /// Ensures that the signer of the message has a view of the chain that is compatible with ours.
-pub fn generate_signed_message(slot: u64,
-                           parent_hashes: &[Hash256],
-                           shard_id: u16,
-                           shard_block_hash: &Hash256,
-                           justified_slot: u64)
+pub fn generate_signed_message(
+    slot: u64,
+    parent_hashes: &[Hash256],
+    shard_id: u16,
+    shard_block_hash: &Hash256,
+    justified_slot: u64)
     -> Vec<u8>
 {
     /*
@@ -30,3 +31,40 @@ pub fn generate_signed_message(slot: u64,
     let bytes = ssz_stream.drain();
     canonical_hash(&bytes)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_generate_signed_message() {
+        let slot = 93;
+        let parent_hashes: Vec<Hash256> = (0..12)
+            .map(|i| Hash256::from(i as u64))
+            .collect();
+        let shard_id = 15;
+        let shard_block_hash = Hash256::from("shard_block_hash".as_bytes());
+        let justified_slot = 18;
+
+        let output = generate_signed_message(
+            slot,
+            &parent_hashes,
+            shard_id,
+            &shard_block_hash,
+            justified_slot);
+
+        /*
+         * Note: this is not some well-known test vector, it's simply the result of running
+         * this and printing the output.
+         *
+         * Once well-known test vectors are established, they should be placed here.
+         */
+        let expected = vec![
+            149, 99, 94, 229, 72, 144, 233, 14, 164, 16, 143, 53, 94, 48,
+            118, 179, 33, 181, 172, 215, 2, 191, 176, 18, 188, 172, 137,
+            178, 236, 66, 74, 120
+        ];
+
+        assert_eq!(output, expected);
+    }
+}