From 8e1380d7c4ad9afe10db13735ce52c2d6ab380cd Mon Sep 17 00:00:00 2001
From: Paul Hauner <paul@paulhauner.com>
Date: Sat, 2 Mar 2019 18:36:44 +1100
Subject: [PATCH] Add ProposerSlashingBuilder

It is capable of producing double votes
---
 eth2/types/src/proposer_slashing.rs         |  4 ++
 eth2/types/src/proposer_slashing/builder.rs | 48 +++++++++++++++++++++
 2 files changed, 52 insertions(+)
 create mode 100644 eth2/types/src/proposer_slashing/builder.rs

diff --git a/eth2/types/src/proposer_slashing.rs b/eth2/types/src/proposer_slashing.rs
index 610017c0c..ea30d46ec 100644
--- a/eth2/types/src/proposer_slashing.rs
+++ b/eth2/types/src/proposer_slashing.rs
@@ -6,6 +6,10 @@ use serde_derive::Serialize;
 use ssz_derive::{Decode, Encode, TreeHash};
 use test_random_derive::TestRandom;
 
+mod builder;
+
+pub use builder::ProposerSlashingBuilder;
+
 #[derive(Debug, PartialEq, Clone, Serialize, Encode, Decode, TreeHash, TestRandom)]
 pub struct ProposerSlashing {
     pub proposer_index: u64,
diff --git a/eth2/types/src/proposer_slashing/builder.rs b/eth2/types/src/proposer_slashing/builder.rs
new file mode 100644
index 000000000..a43a73ff0
--- /dev/null
+++ b/eth2/types/src/proposer_slashing/builder.rs
@@ -0,0 +1,48 @@
+use crate::*;
+use ssz::TreeHash;
+
+pub struct ProposerSlashingBuilder();
+
+impl ProposerSlashingBuilder {
+    pub fn double_vote<F>(proposer_index: u64, signer: F, spec: &ChainSpec) -> ProposerSlashing
+    where
+        F: Fn(u64, &[u8], Epoch, u64) -> Signature,
+    {
+        let slot = Slot::new(0);
+        let shard = 0;
+
+        let proposal_data_1 = ProposalSignedData {
+            slot,
+            shard,
+            block_root: Hash256::from("one".as_bytes()),
+        };
+
+        let proposal_data_2 = ProposalSignedData {
+            slot,
+            shard,
+            block_root: Hash256::from("two".as_bytes()),
+        };
+
+        let proposal_signature_1 = {
+            let message = proposal_data_1.hash_tree_root();
+            let epoch = slot.epoch(spec.epoch_length);
+            let domain = spec.domain_proposal;
+            signer(proposer_index, &message[..], epoch, domain)
+        };
+
+        let proposal_signature_2 = {
+            let message = proposal_data_2.hash_tree_root();
+            let epoch = slot.epoch(spec.epoch_length);
+            let domain = spec.domain_proposal;
+            signer(proposer_index, &message[..], epoch, domain)
+        };
+
+        ProposerSlashing {
+            proposer_index,
+            proposal_data_1,
+            proposal_signature_1,
+            proposal_data_2,
+            proposal_signature_2,
+        }
+    }
+}