Fix SigVerifiedOp SSZ implementation (#6035)

* Fix SigVerifiedOp SSZ implementation

consensus/types/src/attester_slashing.rs

@@ -3,6 +3,7 @@ use crate::indexed_attestation::{
 };
 use crate::{test_utils::TestRandom, EthSpec};
 use derivative::Derivative;
+use rand::{Rng, RngCore};
 use serde::{Deserialize, Serialize};
 use ssz_derive::{Decode, Encode};
 use superstruct::superstruct;
@@ -160,6 +161,16 @@ impl<E: EthSpec> AttesterSlashing<E> {
     }
 }
 
+impl<E: EthSpec> TestRandom for AttesterSlashing<E> {
+    fn random_for_test(rng: &mut impl RngCore) -> Self {
+        if rng.gen_bool(0.5) {
+            AttesterSlashing::Base(AttesterSlashingBase::random_for_test(rng))
+        } else {
+            AttesterSlashing::Electra(AttesterSlashingElectra::random_for_test(rng))
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

consensus/types/src/test_utils/test_random.rs

@@ -2,6 +2,7 @@ use crate::*;
 use rand::RngCore;
 use rand::SeedableRng;
 use rand_xorshift::XorShiftRng;
+use smallvec::{smallvec, SmallVec};
 use std::marker::PhantomData;
 use std::sync::Arc;
 
@@ -118,6 +119,21 @@ where
     }
 }
 
+impl<U, const N: usize> TestRandom for SmallVec<[U; N]>
+where
+    U: TestRandom,
+{
+    fn random_for_test(rng: &mut impl RngCore) -> Self {
+        let mut output = smallvec![];
+
+        for _ in 0..(usize::random_for_test(rng) % 4) {
+            output.push(<U>::random_for_test(rng));
+        }
+
+        output
+    }
+}
+
 macro_rules! impl_test_random_for_u8_array {
     ($len: expr) => {
         impl TestRandom for [u8; $len] {