Migrate MerkleProof tests among other testing utilities (#4689)

test/helpers/eip712.js

@@ -1,5 +1,4 @@
-const ethSigUtil = require('eth-sig-util');
-const keccak256 = require('keccak256');
+const { ethers } = require('ethers');
 
 const EIP712Domain = [
   { name: 'name', type: 'string' },
@@ -17,14 +16,6 @@ const Permit = [
   { name: 'deadline', type: 'uint256' },
 ];
 
-function bufferToHexString(buffer) {
-  return '0x' + buffer.toString('hex');
-}
-
-function hexStringToBuffer(hexstr) {
-  return Buffer.from(hexstr.replace(/^0x/, ''), 'hex');
-}
-
 async function getDomain(contract) {
   const { fields, name, version, chainId, verifyingContract, salt, extensions } = await contract.eip712Domain();
 
@@ -32,7 +23,15 @@ async function getDomain(contract) {
     throw Error('Extensions not implemented');
   }
 
-  const domain = { name, version, chainId, verifyingContract, salt };
+  const domain = {
+    name,
+    version,
+    // TODO: remove check when contracts are all migrated to ethers
+    chainId: web3.utils.isBN(chainId) ? chainId.toNumber() : chainId,
+    verifyingContract,
+    salt,
+  };
+
   for (const [i, { name }] of EIP712Domain.entries()) {
     if (!(fields & (1 << i))) {
       delete domain[name];
@@ -46,15 +45,9 @@ function domainType(domain) {
   return EIP712Domain.filter(({ name }) => domain[name] !== undefined);
 }
 
-function domainSeparator(domain) {
-  return bufferToHexString(
-    ethSigUtil.TypedDataUtils.hashStruct('EIP712Domain', domain, { EIP712Domain: domainType(domain) }),
-  );
-}
-
 function hashTypedData(domain, structHash) {
-  return bufferToHexString(
-    keccak256(Buffer.concat(['0x1901', domainSeparator(domain), structHash].map(str => hexStringToBuffer(str)))),
+  return ethers.keccak256(
+    Buffer.concat(['0x1901', ethers.TypedDataEncoder.hashDomain(domain), structHash].map(ethers.toBeArray)),
   );
 }
 
@@ -62,6 +55,6 @@ module.exports = {
   Permit,
   getDomain,
   domainType,
-  domainSeparator,
+  domainSeparator: ethers.TypedDataEncoder.hashDomain,
   hashTypedData,
 };