Add AttestationSlashingBuilder

eth2/types/src/attester_slashing.rs

@@ -1,9 +1,13 @@
-use crate::{test_utils::TestRandom, ChainSpec, SlashableAttestation};
+use crate::{test_utils::TestRandom, SlashableAttestation};
 use rand::RngCore;
 use serde_derive::Serialize;
 use ssz_derive::{Decode, Encode, TreeHash};
 use test_random_derive::TestRandom;
 
+mod builder;
+
+pub use builder::AttesterSlashingBuilder;
+
 #[derive(Debug, PartialEq, Clone, Serialize, Encode, Decode, TreeHash, TestRandom)]
 pub struct AttesterSlashing {
     pub slashable_attestation_1: SlashableAttestation,

eth2/types/src/attester_slashing/builder.rs

@@ -0,0 +1,85 @@
+use crate::*;
+use ssz::TreeHash;
+
+pub struct AttesterSlashingBuilder();
+
+impl AttesterSlashingBuilder {
+    pub fn double_vote<F>(
+        validator_indices: &[u64],
+        signer: F,
+        spec: &ChainSpec,
+    ) -> AttesterSlashing
+    where
+        F: Fn(u64, &[u8], Epoch, u64) -> Signature,
+    {
+        let double_voted_slot = Slot::new(0);
+        let shard = 0;
+        let justified_epoch = Epoch::new(0);
+        let epoch = Epoch::new(0);
+        let hash_1 = Hash256::from("1".as_bytes());
+        let hash_2 = Hash256::from("2".as_bytes());
+
+        let mut slashable_attestation_1 = SlashableAttestation {
+            validator_indices: validator_indices.to_vec(),
+            data: AttestationData {
+                slot: double_voted_slot,
+                shard,
+                beacon_block_root: hash_1,
+                epoch_boundary_root: hash_1,
+                shard_block_root: hash_1,
+                latest_crosslink: Crosslink {
+                    epoch,
+                    shard_block_root: hash_1,
+                },
+                justified_epoch,
+                justified_block_root: hash_1,
+            },
+            custody_bitfield: Bitfield::new(),
+            aggregate_signature: AggregateSignature::new(),
+        };
+
+        let mut slashable_attestation_2 = SlashableAttestation {
+            validator_indices: validator_indices.to_vec(),
+            data: AttestationData {
+                slot: double_voted_slot,
+                shard,
+                beacon_block_root: hash_2,
+                epoch_boundary_root: hash_2,
+                shard_block_root: hash_2,
+                latest_crosslink: Crosslink {
+                    epoch,
+                    shard_block_root: hash_2,
+                },
+                justified_epoch,
+                justified_block_root: hash_2,
+            },
+            custody_bitfield: Bitfield::new(),
+            aggregate_signature: AggregateSignature::new(),
+        };
+
+        let add_signatures = |attestation: &mut SlashableAttestation| {
+            for (i, validator_index) in validator_indices.iter().enumerate() {
+                let attestation_data_and_custody_bit = AttestationDataAndCustodyBit {
+                    data: attestation.data.clone(),
+                    custody_bit: attestation.custody_bitfield.get(i).unwrap(),
+                };
+                let message = attestation_data_and_custody_bit.hash_tree_root();
+                let signature = signer(
+                    *validator_index,
+                    &message[..],
+                    epoch,
+                    spec.domain_attestation,
+                );
+                attestation.aggregate_signature.add(&signature);
+            }
+        };
+
+        add_signatures(&mut slashable_attestation_1);
+        add_signatures(&mut slashable_attestation_2);
+
+        AttesterSlashing {
+            slashable_attestation_1,
+            slashable_attestation_2,
+        }
+    }
+}