Make ERC20Votes independent from ERC20Permit (#3816)

Co-authored-by: Francisco <frangio.1@gmail.com>

CHANGELOG.md

@@ -3,6 +3,8 @@
 ## Unreleased (Breaking)
 
  * `TimelockController`: Changed the role architecture to use `DEFAULT_ADMIN_ROLE` as the admin for all roles, instead of the bespoke `TIMELOCK_ADMIN_ROLE` that was used previously. This aligns with the general recommendation for `AccessControl` and makes the addition of new roles easier. Accordingly, the `admin` parameter and timelock will now be granted `DEFAULT_ADMIN_ROLE` instead of `TIMELOCK_ADMIN_ROLE`. ([#3799](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3799))
+ * `ERC20Votes`: Changed internal vote accounting to reusable `Votes` module previously used by `ERC721Votes`. Removed implicit `ERC20Permit` inheritance. [#3816](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3816)
+ * `Nonces`: Added a new contract to keep track of user nonces. Used for signatures in `ERC20Permit`, `ERC20Votes`, and `ERC721Votes`. ([#3816](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3816))
  * Removed presets in favor of [OpenZeppelin Contracts Wizard](https://wizard.openzeppelin.com/).
  * `TransparentUpgradeableProxy`: Removed `admin` and `implementation` getters, which were only callable by the proxy owner and thus not very useful. ([#3820](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3820))
  * `ProxyAdmin`: Removed `getProxyAdmin` and `getProxyImplementation` getters. ([#3820](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3820))

contracts/governance/utils/Votes.sol

@@ -3,10 +3,11 @@
 pragma solidity ^0.8.0;
 
 import "../../utils/Context.sol";
-import "../../utils/Counters.sol";
+import "../../utils/Nonces.sol";
 import "../../utils/Checkpoints.sol";
 import "../../utils/cryptography/EIP712.sol";
 import "./IVotes.sol";
+import "../../utils/math/SafeCast.sol";
 
 /**
  * @dev This is a base abstract contract that tracks voting units, which are a measure of voting power that can be
@@ -28,9 +29,8 @@ import "./IVotes.sol";
  *
  * _Available since v4.5._
  */
-abstract contract Votes is IVotes, Context, EIP712 {
+abstract contract Votes is IVotes, Context, EIP712, Nonces {
     using Checkpoints for Checkpoints.History;
-    using Counters for Counters.Counter;
 
     bytes32 private constant _DELEGATION_TYPEHASH =
         keccak256("Delegation(address delegatee,uint256 nonce,uint256 expiry)");
@@ -39,8 +39,6 @@ abstract contract Votes is IVotes, Context, EIP712 {
     mapping(address => Checkpoints.History) private _delegateCheckpoints;
     Checkpoints.History private _totalCheckpoints;
 
-    mapping(address => Counters.Counter) private _nonces;
-
     /**
      * @dev Returns the current amount of votes that `account` has.
      */
@@ -170,30 +168,26 @@ abstract contract Votes is IVotes, Context, EIP712 {
         }
     }
 
-    function _add(uint256 a, uint256 b) private pure returns (uint256) {
-        return a + b;
-    }
-
-    function _subtract(uint256 a, uint256 b) private pure returns (uint256) {
-        return a - b;
-    }
-
     /**
-     * @dev Consumes a nonce.
-     *
-     * Returns the current value and increments nonce.
+     * @dev Get number of checkpoints for `account`.
      */
-    function _useNonce(address owner) internal virtual returns (uint256 current) {
-        Counters.Counter storage nonce = _nonces[owner];
-        current = nonce.current();
-        nonce.increment();
+    function _numCheckpoints(address account) internal view virtual returns (uint32) {
+        return SafeCast.toUint32(_delegateCheckpoints[account].length());
     }
 
     /**
-     * @dev Returns an address nonce.
+     * @dev Get the `pos`-th checkpoint for `account`.
      */
-    function nonces(address owner) public view virtual returns (uint256) {
-        return _nonces[owner].current();
+    function _checkpoints(address account, uint32 pos) internal view virtual returns (Checkpoints.Checkpoint memory) {
+        return _delegateCheckpoints[account].getAtPosition(pos);
+    }
+
+    function _add(uint256 a, uint256 b) private pure returns (uint256) {
+        return a + b;
+    }
+
+    function _subtract(uint256 a, uint256 b) private pure returns (uint256) {
+        return a - b;
     }
 
     /**

contracts/mocks/ERC20VotesCompMock.sol

@@ -5,7 +5,7 @@ pragma solidity ^0.8.0;
 import "../token/ERC20/extensions/ERC20VotesComp.sol";
 
 contract ERC20VotesCompMock is ERC20VotesComp {
-    constructor(string memory name, string memory symbol) ERC20(name, symbol) ERC20Permit(name) {}
+    constructor(string memory name, string memory symbol) ERC20(name, symbol) EIP712(name, "1") {}
 
     function mint(address account, uint256 amount) public {
         _mint(account, amount);

contracts/mocks/ERC20VotesMock.sol

@@ -5,7 +5,7 @@ pragma solidity ^0.8.0;
 import "../token/ERC20/extensions/ERC20Votes.sol";
 
 contract ERC20VotesMock is ERC20Votes {
-    constructor(string memory name, string memory symbol) ERC20(name, symbol) ERC20Permit(name) {}
+    constructor(string memory name, string memory symbol) ERC20(name, symbol) EIP712(name, "1") {}
 
     function mint(address account, uint256 amount) public {
         _mint(account, amount);

contracts/mocks/ERC721VotesMock.sol

@@ -15,7 +15,7 @@ contract ERC721VotesMock is ERC721Votes {
         _mint(account, tokenId);
     }
 
-    function burn(uint256 tokenId) public {
+    function burn(address, uint256 tokenId) public {
         _burn(tokenId);
     }
 

contracts/mocks/NoncesImpl.sol

@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../utils/Nonces.sol";
+
+contract NoncesImpl is Nonces {
+    function useNonce(address owner) public {
+        super._useNonce(owner);
+    }
+}

contracts/mocks/VotesMock.sol

@@ -28,7 +28,7 @@ contract VotesMock is Votes {
         _transferVotingUnits(address(0), account, 1);
     }
 
-    function burn(uint256 voteId) external {
+    function burn(address, uint256 voteId) external {
         address owner = _owners[voteId];
         _balances[owner] -= 1;
         _transferVotingUnits(owner, address(0), 1);

contracts/token/ERC20/extensions/ERC20Permit.sol

@@ -7,7 +7,7 @@ import "./IERC20Permit.sol";
 import "../ERC20.sol";
 import "../../../utils/cryptography/ECDSA.sol";
 import "../../../utils/cryptography/EIP712.sol";
-import "../../../utils/Counters.sol";
+import "../../../utils/Nonces.sol";
 
 /**
  * @dev Implementation of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
@@ -19,11 +19,7 @@ import "../../../utils/Counters.sol";
  *
  * _Available since v3.4._
  */
-abstract contract ERC20Permit is ERC20, IERC20Permit, EIP712 {
-    using Counters for Counters.Counter;
-
-    mapping(address => Counters.Counter) private _nonces;
-
+abstract contract ERC20Permit is ERC20, IERC20Permit, EIP712, Nonces {
     // solhint-disable-next-line var-name-mixedcase
     bytes32 private constant _PERMIT_TYPEHASH =
         keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
@@ -70,8 +66,8 @@ abstract contract ERC20Permit is ERC20, IERC20Permit, EIP712 {
     /**
      * @dev See {IERC20Permit-nonces}.
      */
-    function nonces(address owner) public view virtual override returns (uint256) {
-        return _nonces[owner].current();
+    function nonces(address owner) public view virtual override(IERC20Permit, Nonces) returns (uint256) {
+        return super.nonces(owner);
     }
 
     /**
@@ -81,15 +77,4 @@ abstract contract ERC20Permit is ERC20, IERC20Permit, EIP712 {
     function DOMAIN_SEPARATOR() external view override returns (bytes32) {
         return _domainSeparatorV4();
     }
-
-    /**
-     * @dev "Consume a nonce": return the current value and increment.
-     *
-     * _Available since v4.1._
-     */
-    function _useNonce(address owner) internal virtual returns (uint256 current) {
-        Counters.Counter storage nonce = _nonces[owner];
-        current = nonce.current();
-        nonce.increment();
-    }
 }

contracts/token/ERC20/extensions/ERC20Votes.sol

@@ -3,11 +3,9 @@
 
 pragma solidity ^0.8.0;
 
-import "./ERC20Permit.sol";
-import "../../../utils/math/Math.sol";
-import "../../../governance/utils/IVotes.sol";
+import "../ERC20.sol";
+import "../../../governance/utils/Votes.sol";
 import "../../../utils/math/SafeCast.sol";
-import "../../../utils/cryptography/ECDSA.sol";
 
 /**
  * @dev Extension of ERC20 to support Compound-like voting and delegation. This version is more generic than Compound's,
@@ -24,148 +22,7 @@ import "../../../utils/cryptography/ECDSA.sol";
  *
  * _Available since v4.2._
  */
-abstract contract ERC20Votes is IVotes, ERC20Permit {
-    struct Checkpoint {
-        uint32 fromBlock;
-        uint224 votes;
-    }
-
-    bytes32 private constant _DELEGATION_TYPEHASH =
-        keccak256("Delegation(address delegatee,uint256 nonce,uint256 expiry)");
-
-    mapping(address => address) private _delegates;
-    mapping(address => Checkpoint[]) private _checkpoints;
-    Checkpoint[] private _totalSupplyCheckpoints;
-
-    /**
-     * @dev Get the `pos`-th checkpoint for `account`.
-     */
-    function checkpoints(address account, uint32 pos) public view virtual returns (Checkpoint memory) {
-        return _checkpoints[account][pos];
-    }
-
-    /**
-     * @dev Get number of checkpoints for `account`.
-     */
-    function numCheckpoints(address account) public view virtual returns (uint32) {
-        return SafeCast.toUint32(_checkpoints[account].length);
-    }
-
-    /**
-     * @dev Get the address `account` is currently delegating to.
-     */
-    function delegates(address account) public view virtual override returns (address) {
-        return _delegates[account];
-    }
-
-    /**
-     * @dev Gets the current votes balance for `account`
-     */
-    function getVotes(address account) public view virtual override returns (uint256) {
-        uint256 pos = _checkpoints[account].length;
-        unchecked {
-            return pos == 0 ? 0 : _checkpoints[account][pos - 1].votes;
-        }
-    }
-
-    /**
-     * @dev Retrieve the number of votes for `account` at the end of `blockNumber`.
-     *
-     * Requirements:
-     *
-     * - `blockNumber` must have been already mined
-     */
-    function getPastVotes(address account, uint256 blockNumber) public view virtual override returns (uint256) {
-        require(blockNumber < block.number, "ERC20Votes: block not yet mined");
-        return _checkpointsLookup(_checkpoints[account], blockNumber);
-    }
-
-    /**
-     * @dev Retrieve the `totalSupply` at the end of `blockNumber`. Note, this value is the sum of all balances.
-     * It is NOT the sum of all the delegated votes!
-     *
-     * Requirements:
-     *
-     * - `blockNumber` must have been already mined
-     */
-    function getPastTotalSupply(uint256 blockNumber) public view virtual override returns (uint256) {
-        require(blockNumber < block.number, "ERC20Votes: block not yet mined");
-        return _checkpointsLookup(_totalSupplyCheckpoints, blockNumber);
-    }
-
-    /**
-     * @dev Lookup a value in a list of (sorted) checkpoints.
-     */
-    function _checkpointsLookup(Checkpoint[] storage ckpts, uint256 blockNumber) private view returns (uint256) {
-        // We run a binary search to look for the earliest checkpoint taken after `blockNumber`.
-        //
-        // Initially we check if the block is recent to narrow the search range.
-        // During the loop, the index of the wanted checkpoint remains in the range [low-1, high).
-        // With each iteration, either `low` or `high` is moved towards the middle of the range to maintain the invariant.
-        // - If the middle checkpoint is after `blockNumber`, we look in [low, mid)
-        // - If the middle checkpoint is before or equal to `blockNumber`, we look in [mid+1, high)
-        // Once we reach a single value (when low == high), we've found the right checkpoint at the index high-1, if not
-        // out of bounds (in which case we're looking too far in the past and the result is 0).
-        // Note that if the latest checkpoint available is exactly for `blockNumber`, we end up with an index that is
-        // past the end of the array, so we technically don't find a checkpoint after `blockNumber`, but it works out
-        // the same.
-        uint256 length = ckpts.length;
-
-        uint256 low = 0;
-        uint256 high = length;
-
-        if (length > 5) {
-            uint256 mid = length - Math.sqrt(length);
-            if (_unsafeAccess(ckpts, mid).fromBlock > blockNumber) {
-                high = mid;
-            } else {
-                low = mid + 1;
-            }
-        }
-
-        while (low < high) {
-            uint256 mid = Math.average(low, high);
-            if (_unsafeAccess(ckpts, mid).fromBlock > blockNumber) {
-                high = mid;
-            } else {
-                low = mid + 1;
-            }
-        }
-
-        unchecked {
-            return high == 0 ? 0 : _unsafeAccess(ckpts, high - 1).votes;
-        }
-    }
-
-    /**
-     * @dev Delegate votes from the sender to `delegatee`.
-     */
-    function delegate(address delegatee) public virtual override {
-        _delegate(_msgSender(), delegatee);
-    }
-
-    /**
-     * @dev Delegates votes from signer to `delegatee`
-     */
-    function delegateBySig(
-        address delegatee,
-        uint256 nonce,
-        uint256 expiry,
-        uint8 v,
-        bytes32 r,
-        bytes32 s
-    ) public virtual override {
-        require(block.timestamp <= expiry, "ERC20Votes: signature expired");
-        address signer = ECDSA.recover(
-            _hashTypedDataV4(keccak256(abi.encode(_DELEGATION_TYPEHASH, delegatee, nonce, expiry))),
-            v,
-            r,
-            s
-        );
-        require(nonce == _useNonce(signer), "ERC20Votes: invalid nonce");
-        _delegate(signer, delegatee);
-    }
-
+abstract contract ERC20Votes is ERC20, Votes {
     /**
      * @dev Maximum token supply. Defaults to `type(uint224).max` (2^224^ - 1).
      */
@@ -173,25 +30,6 @@ abstract contract ERC20Votes is IVotes, ERC20Permit {
         return type(uint224).max;
     }
 
-    /**
-     * @dev Snapshots the totalSupply after it has been increased.
-     */
-    function _mint(address account, uint256 amount) internal virtual override {
-        super._mint(account, amount);
-        require(totalSupply() <= _maxSupply(), "ERC20Votes: total supply risks overflowing votes");
-
-        _writeCheckpoint(_totalSupplyCheckpoints, _add, amount);
-    }
-
-    /**
-     * @dev Snapshots the totalSupply after it has been decreased.
-     */
-    function _burn(address account, uint256 amount) internal virtual override {
-        super._burn(account, amount);
-
-        _writeCheckpoint(_totalSupplyCheckpoints, _subtract, amount);
-    }
-
     /**
      * @dev Move voting power when tokens are transferred.
      *
@@ -202,79 +40,36 @@ abstract contract ERC20Votes is IVotes, ERC20Permit {
         address to,
         uint256 amount
     ) internal virtual override {
+        _transferVotingUnits(from, to, amount);
         super._afterTokenTransfer(from, to, amount);
-
-        _moveVotingPower(delegates(from), delegates(to), amount);
     }
 
     /**
-     * @dev Change delegation for `delegator` to `delegatee`.
-     *
-     * Emits events {IVotes-DelegateChanged} and {IVotes-DelegateVotesChanged}.
+     * @dev Get number of checkpoints for `account`.
      */
-    function _delegate(address delegator, address delegatee) internal virtual {
-        address currentDelegate = delegates(delegator);
-        uint256 delegatorBalance = balanceOf(delegator);
-        _delegates[delegator] = delegatee;
-
-        emit DelegateChanged(delegator, currentDelegate, delegatee);
-
-        _moveVotingPower(currentDelegate, delegatee, delegatorBalance);
-    }
-
-    function _moveVotingPower(
-        address src,
-        address dst,
-        uint256 amount
-    ) private {
-        if (src != dst && amount > 0) {
-            if (src != address(0)) {
-                (uint256 oldWeight, uint256 newWeight) = _writeCheckpoint(_checkpoints[src], _subtract, amount);
-                emit DelegateVotesChanged(src, oldWeight, newWeight);
-            }
-
-            if (dst != address(0)) {
-                (uint256 oldWeight, uint256 newWeight) = _writeCheckpoint(_checkpoints[dst], _add, amount);
-                emit DelegateVotesChanged(dst, oldWeight, newWeight);
-            }
-        }
-    }
-
-    function _writeCheckpoint(
-        Checkpoint[] storage ckpts,
-        function(uint256, uint256) view returns (uint256) op,
-        uint256 delta
-    ) private returns (uint256 oldWeight, uint256 newWeight) {
-        uint256 pos = ckpts.length;
-
-        unchecked {
-            Checkpoint memory oldCkpt = pos == 0 ? Checkpoint(0, 0) : _unsafeAccess(ckpts, pos - 1);
-
-            oldWeight = oldCkpt.votes;
-            newWeight = op(oldWeight, delta);
-
-            if (pos > 0 && oldCkpt.fromBlock == block.number) {
-                _unsafeAccess(ckpts, pos - 1).votes = SafeCast.toUint224(newWeight);
-            } else {
-                ckpts.push(
-                    Checkpoint({fromBlock: SafeCast.toUint32(block.number), votes: SafeCast.toUint224(newWeight)})
-                );
-            }
-        }
+    function numCheckpoints(address account) public view virtual returns (uint32) {
+        return _numCheckpoints(account);
     }
 
-    function _add(uint256 a, uint256 b) private pure returns (uint256) {
-        return a + b;
+    /**
+     * @dev Get the `pos`-th checkpoint for `account`.
+     */
+    function checkpoints(address account, uint32 pos) public view virtual returns (Checkpoints.Checkpoint memory) {
+        return _checkpoints(account, pos);
     }
 
-    function _subtract(uint256 a, uint256 b) private pure returns (uint256) {
-        return a - b;
+    /**
+     * @dev Returns the balance of `account`.
+     */
+    function _getVotingUnits(address account) internal view virtual override returns (uint256) {
+        return balanceOf(account);
     }
 
-    function _unsafeAccess(Checkpoint[] storage ckpts, uint256 pos) private pure returns (Checkpoint storage result) {
-        assembly {
-            mstore(0, ckpts.slot)
-            result.slot := add(keccak256(0, 0x20), pos)
-        }
+    /**
+     * @dev Snapshots the totalSupply after it has been increased.
+     */
+    function _mint(address account, uint256 amount) internal virtual override {
+        super._mint(account, amount);
+        require(totalSupply() <= _maxSupply(), "ERC20Votes: total supply risks overflowing votes");
     }
 }

contracts/utils/Checkpoints.sol

@@ -68,6 +68,13 @@ library Checkpoints {
         return pos == 0 ? 0 : _unsafeAccess(self._checkpoints, pos - 1)._value;
     }
 
+    /**
+     * @dev Returns checkpoint at given position.
+     */
+    function getAtPosition(History storage self, uint32 pos) internal view returns (Checkpoint memory) {
+        return self._checkpoints[pos];
+    }
+
     /**
      * @dev Pushes a value onto a History so that it is stored as the checkpoint for the current block.
      *

contracts/utils/Nonces.sol

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+import "./Counters.sol";
+
+/**
+ * @dev Provides tracking nonces for addresses. Nonces will only increment.
+ */
+abstract contract Nonces {
+    using Counters for Counters.Counter;
+
+    mapping(address => Counters.Counter) private _nonces;
+
+    /**
+     * @dev Returns an address nonce.
+     */
+    function nonces(address owner) public view virtual returns (uint256) {
+        return _nonces[owner].current();
+    }
+
+    /**
+     * @dev Consumes a nonce.
+     *
+     * Returns the current value and increments nonce.
+     */
+    function _useNonce(address owner) internal virtual returns (uint256 current) {
+        Counters.Counter storage nonce = _nonces[owner];
+        current = nonce.current();
+        nonce.increment();
+    }
+}

scripts/generate/templates/Checkpoints.js

@@ -107,6 +107,13 @@ function getAtProbablyRecentBlock(${opts.historyTypeName} storage self, uint256
     return pos == 0 ? 0 : _unsafeAccess(self.${opts.checkpointFieldName}, pos - 1).${opts.valueFieldName};
 }
 
+/**
+ * @dev Returns checkpoint at given position.
+ */
+function getAtPosition(History storage self, uint32 pos) internal view returns (Checkpoint memory) {
+    return self._checkpoints[pos];
+}
+
 /**
  * @dev Pushes a value onto a History so that it is stored as the checkpoint for the current block.
  *

test/governance/utils/Votes.behavior.js

@@ -7,6 +7,7 @@ const ethSigUtil = require('eth-sig-util');
 const Wallet = require('ethereumjs-wallet').default;
 
 const { EIP712Domain, domainSeparator } = require('../../helpers/eip712');
+const { web3 } = require('hardhat');
 
 const Delegation = [
   { name: 'delegatee', type: 'address' },
@@ -45,7 +46,7 @@ function shouldBehaveLikeVotes () {
       });
 
       beforeEach(async function () {
-        await this.votes.mint(delegatorAddress, this.NFT0);
+        await this.votes.mint(delegatorAddress, this.token0);
       });
 
       it('accept signed delegation', async function () {
@@ -151,7 +152,7 @@ function shouldBehaveLikeVotes () {
     describe('set delegation', function () {
       describe('call', function () {
         it('delegation with tokens', async function () {
-          await this.votes.mint(this.account1, this.NFT0);
+          await this.votes.mint(this.account1, this.token0);
           expect(await this.votes.delegates(this.account1)).to.be.equal(ZERO_ADDRESS);
 
           const { receipt } = await this.votes.delegate(this.account1, { from: this.account1 });
@@ -192,7 +193,7 @@ function shouldBehaveLikeVotes () {
 
     describe('change delegation', function () {
       beforeEach(async function () {
-        await this.votes.mint(this.account1, this.NFT0);
+        await this.votes.mint(this.account1, this.token0);
         await this.votes.delegate(this.account1, { from: this.account1 });
       });
 
@@ -245,7 +246,7 @@ function shouldBehaveLikeVotes () {
       });
 
       it('returns the latest block if >= last checkpoint block', async function () {
-        const t1 = await this.votes.mint(this.account1, this.NFT0);
+        const t1 = await this.votes.mint(this.account1, this.token0);
         await time.advanceBlock();
         await time.advanceBlock();
 
@@ -255,7 +256,7 @@ function shouldBehaveLikeVotes () {
 
       it('returns zero if < first checkpoint block', async function () {
         await time.advanceBlock();
-        const t2 = await this.votes.mint(this.account1, this.NFT1);
+        const t2 = await this.votes.mint(this.account1, this.token1);
         await time.advanceBlock();
         await time.advanceBlock();
 
@@ -264,19 +265,19 @@ function shouldBehaveLikeVotes () {
       });
 
       it('generally returns the voting balance at the appropriate checkpoint', async function () {
-        const t1 = await this.votes.mint(this.account1, this.NFT1);
+        const t1 = await this.votes.mint(this.account1, this.token1);
         await time.advanceBlock();
         await time.advanceBlock();
-        const t2 = await this.votes.burn(this.NFT1);
+        const t2 = await this.votes.burn(this.account1, this.token1);
         await time.advanceBlock();
         await time.advanceBlock();
-        const t3 = await this.votes.mint(this.account1, this.NFT2);
+        const t3 = await this.votes.mint(this.account1, this.token2);
         await time.advanceBlock();
         await time.advanceBlock();
-        const t4 = await this.votes.burn(this.NFT2);
+        const t4 = await this.votes.burn(this.account1, this.token2);
         await time.advanceBlock();
         await time.advanceBlock();
-        const t5 = await this.votes.mint(this.account1, this.NFT3);
+        const t5 = await this.votes.mint(this.account1, this.token3);
         await time.advanceBlock();
         await time.advanceBlock();
 
@@ -298,10 +299,10 @@ function shouldBehaveLikeVotes () {
     // https://github.com/compound-finance/compound-protocol/blob/master/tests/Governance/CompTest.js.
     describe('Compound test suite', function () {
       beforeEach(async function () {
-        await this.votes.mint(this.account1, this.NFT0);
-        await this.votes.mint(this.account1, this.NFT1);
-        await this.votes.mint(this.account1, this.NFT2);
-        await this.votes.mint(this.account1, this.NFT3);
+        await this.votes.mint(this.account1, this.token0);
+        await this.votes.mint(this.account1, this.token1);
+        await this.votes.mint(this.account1, this.token2);
+        await this.votes.mint(this.account1, this.token3);
       });
 
       describe('getPastVotes', function () {

test/governance/utils/Votes.test.js

@@ -50,10 +50,10 @@ contract('Votes', function (accounts) {
       this.account1 = account1;
       this.account2 = account2;
       this.account1Delegatee = account2;
-      this.NFT0 = new BN('10000000000000000000000000');
-      this.NFT1 = new BN('10');
-      this.NFT2 = new BN('20');
-      this.NFT3 = new BN('30');
+      this.token0 = new BN('10000000000000000000000000');
+      this.token1 = new BN('10');
+      this.token2 = new BN('20');
+      this.token3 = new BN('30');
     });
 
     shouldBehaveLikeVotes();

test/token/ERC20/extensions/ERC20Votes.test.js

@@ -2,8 +2,9 @@
 
 const { BN, constants, expectEvent, expectRevert, time } = require('@openzeppelin/test-helpers');
 const { expect } = require('chai');
-const { MAX_UINT256, ZERO_ADDRESS, ZERO_BYTES32 } = constants;
+const { MAX_UINT256, ZERO_ADDRESS } = constants;
 
+const { shouldBehaveLikeVotes } = require('../../../governance/utils/Votes.behavior');
 const { fromRpcSig } = require('ethereumjs-util');
 const ethSigUtil = require('eth-sig-util');
 const Wallet = require('ethereumjs-wallet').default;
@@ -52,7 +53,7 @@ contract('ERC20Votes', function (accounts) {
     const amount = new BN('2').pow(new BN('224'));
     await expectRevert(
       this.token.mint(holder, amount),
-      'ERC20Votes: total supply risks overflowing votes',
+      "SafeCast: value doesn't fit in 224 bits",
     );
   });
 
@@ -62,7 +63,6 @@ contract('ERC20Votes', function (accounts) {
       await this.token.mint(holder, 1);
     }
     const block = await web3.eth.getBlockNumber();
-    expect(await this.token.numCheckpoints(holder)).to.be.bignumber.equal('6');
     // recent
     expect(await this.token.getPastVotes(holder, block - 1)).to.be.bignumber.equal('5');
     // non-recent
@@ -172,7 +172,7 @@ contract('ERC20Votes', function (accounts) {
 
         await expectRevert(
           this.token.delegateBySig(delegatorAddress, nonce, MAX_UINT256, v, r, s),
-          'ERC20Votes: invalid nonce',
+          'Votes: invalid nonce',
         );
       });
 
@@ -204,7 +204,7 @@ contract('ERC20Votes', function (accounts) {
         ));
         await expectRevert(
           this.token.delegateBySig(delegatorAddress, nonce + 1, MAX_UINT256, v, r, s),
-          'ERC20Votes: invalid nonce',
+          'Votes: invalid nonce',
         );
       });
 
@@ -221,7 +221,7 @@ contract('ERC20Votes', function (accounts) {
 
         await expectRevert(
           this.token.delegateBySig(delegatorAddress, nonce, expiry, v, r, s),
-          'ERC20Votes: signature expired',
+          'Votes: signature expired',
         );
       });
     });
@@ -341,12 +341,6 @@ contract('ERC20Votes', function (accounts) {
       await this.token.mint(holder, supply);
     });
 
-    describe('balanceOf', function () {
-      it('grants to initial account', async function () {
-        expect(await this.token.balanceOf(holder)).to.be.bignumber.equal('10000000000000000000000000');
-      });
-    });
-
     describe('numCheckpoints', function () {
       it('returns the number of checkpoints for a delegate', async function () {
         await this.token.transfer(recipient, '100', { from: holder }); //give an account a few tokens for readability
@@ -354,7 +348,7 @@ contract('ERC20Votes', function (accounts) {
 
         const t1 = await this.token.delegate(other1, { from: recipient });
         expect(await this.token.numCheckpoints(other1)).to.be.bignumber.equal('1');
-
+        
         const t2 = await this.token.transfer(other2, 10, { from: recipient });
         expect(await this.token.numCheckpoints(other1)).to.be.bignumber.equal('2');
 
@@ -396,11 +390,17 @@ contract('ERC20Votes', function (accounts) {
       });
     });
 
+    describe('balanceOf', function () {
+      it('grants to initial account', async function () {
+        expect(await this.token.balanceOf(holder)).to.be.bignumber.equal('10000000000000000000000000');
+      });
+    });
+
     describe('getPastVotes', function () {
       it('reverts if block number >= current block', async function () {
         await expectRevert(
           this.token.getPastVotes(other1, 5e10),
-          'ERC20Votes: block not yet mined',
+          'Checkpoints: block not yet mined',
         );
       });
 
@@ -462,7 +462,7 @@ contract('ERC20Votes', function (accounts) {
     it('reverts if block number >= current block', async function () {
       await expectRevert(
         this.token.getPastTotalSupply(5e10),
-        'ERC20Votes: block not yet mined',
+        'Votes: block not yet mined',
       );
     });
 
@@ -515,4 +515,20 @@ contract('ERC20Votes', function (accounts) {
       expect(await this.token.getPastTotalSupply(t4.receipt.blockNumber + 1)).to.be.bignumber.equal('10000000000000000000000000');
     });
   });
+
+  describe('Voting workflow', function () {
+    beforeEach(async function () {
+      this.account1 = holder;
+      this.account1Delegatee = holderDelegatee;
+      this.account2 = recipient;
+      this.name = 'My Token';
+      this.votes = this.token
+      this.token0 = 1;      
+      this.token1 = 1;
+      this.token2 = 1;
+      this.token3 = 1;
+    });
+
+    shouldBehaveLikeVotes();
+  });
 });

test/token/ERC20/extensions/ERC20VotesComp.test.js

@@ -2,15 +2,16 @@
 
 const { BN, constants, expectEvent, expectRevert, time } = require('@openzeppelin/test-helpers');
 const { expect } = require('chai');
-const { MAX_UINT256, ZERO_ADDRESS, ZERO_BYTES32 } = constants;
+const { MAX_UINT256, ZERO_ADDRESS } = constants;
 
+const { batchInBlock } = require('../../../helpers/txpool');
+const { shouldBehaveLikeVotes } = require('../../../governance/utils/Votes.behavior');
 const { fromRpcSig } = require('ethereumjs-util');
 const ethSigUtil = require('eth-sig-util');
 const Wallet = require('ethereumjs-wallet').default;
 
 const ERC20VotesCompMock = artifacts.require('ERC20VotesCompMock');
 
-const { batchInBlock } = require('../../../helpers/txpool');
 const { EIP712Domain, domainSeparator } = require('../../../helpers/eip712');
 
 const Delegation = [
@@ -52,7 +53,7 @@ contract('ERC20VotesComp', function (accounts) {
     const amount = new BN('2').pow(new BN('96'));
     await expectRevert(
       this.token.mint(holder, amount),
-      'ERC20Votes: total supply risks overflowing votes',
+      "ERC20Votes: total supply risks overflowing votes",
     );
   });
 
@@ -159,7 +160,7 @@ contract('ERC20VotesComp', function (accounts) {
 
         await expectRevert(
           this.token.delegateBySig(delegatorAddress, nonce, MAX_UINT256, v, r, s),
-          'ERC20Votes: invalid nonce',
+          'Votes: invalid nonce',
         );
       });
 
@@ -191,7 +192,7 @@ contract('ERC20VotesComp', function (accounts) {
         ));
         await expectRevert(
           this.token.delegateBySig(delegatorAddress, nonce + 1, MAX_UINT256, v, r, s),
-          'ERC20Votes: invalid nonce',
+          'Votes: invalid nonce',
         );
       });
 
@@ -208,7 +209,7 @@ contract('ERC20VotesComp', function (accounts) {
 
         await expectRevert(
           this.token.delegateBySig(delegatorAddress, nonce, expiry, v, r, s),
-          'ERC20Votes: signature expired',
+          'Votes: signature expired',
         );
       });
     });
@@ -373,12 +374,12 @@ contract('ERC20VotesComp', function (accounts) {
         expect(await this.token.checkpoints(other1, 1)).to.be.deep.equal([ t4.receipt.blockNumber.toString(), '100' ]);
       });
     });
-
+  
     describe('getPriorVotes', function () {
       it('reverts if block number >= current block', async function () {
         await expectRevert(
           this.token.getPriorVotes(other1, 5e10),
-          'ERC20Votes: block not yet mined',
+          'Checkpoints: block not yet mined',
         );
       });
 
@@ -440,7 +441,7 @@ contract('ERC20VotesComp', function (accounts) {
     it('reverts if block number >= current block', async function () {
       await expectRevert(
         this.token.getPastTotalSupply(5e10),
-        'ERC20Votes: block not yet mined',
+        'Votes: block not yet mined',
       );
     });
 
@@ -493,4 +494,20 @@ contract('ERC20VotesComp', function (accounts) {
       expect(await this.token.getPastTotalSupply(t4.receipt.blockNumber + 1)).to.be.bignumber.equal('10000000000000000000000000');
     });
   });
+
+  describe('Voting workflow', function () {
+    beforeEach(async function () {
+      this.account1 = holder;
+      this.account1Delegatee = holderDelegatee;
+      this.account2 = recipient;
+      this.name = 'My Token';
+      this.votes = this.token
+      this.token0 = 1;      
+      this.token1 = 1;
+      this.token2 = 1;
+      this.token3 = 1;
+    });
+
+    shouldBehaveLikeVotes();
+  });
 });

test/token/ERC721/extensions/ERC721Votes.test.js

@@ -3,9 +3,6 @@
 const { BN, expectEvent, time } = require('@openzeppelin/test-helpers');
 const { expect } = require('chai');
 
-const { promisify } = require('util');
-const queue = promisify(setImmediate);
-
 const ERC721VotesMock = artifacts.require('ERC721VotesMock');
 
 const { shouldBehaveLikeVotes } = require('../../../governance/utils/Votes.behavior');
@@ -23,18 +20,18 @@ contract('ERC721Votes', function (accounts) {
     // See https://github.com/trufflesuite/ganache-core/issues/515
     this.chainId = await this.votes.getChainId();
 
-    this.NFT0 = new BN('10000000000000000000000000');
-    this.NFT1 = new BN('10');
-    this.NFT2 = new BN('20');
-    this.NFT3 = new BN('30');
+    this.token0 = new BN('10000000000000000000000000');
+    this.token1 = new BN('10');
+    this.token2 = new BN('20');
+    this.token3 = new BN('30');
   });
 
   describe('balanceOf', function () {
     beforeEach(async function () {
-      await this.votes.mint(account1, this.NFT0);
-      await this.votes.mint(account1, this.NFT1);
-      await this.votes.mint(account1, this.NFT2);
-      await this.votes.mint(account1, this.NFT3);
+      await this.votes.mint(account1, this.token0);
+      await this.votes.mint(account1, this.token1);
+      await this.votes.mint(account1, this.token2);
+      await this.votes.mint(account1, this.token3);
     });
 
     it('grants to initial account', async function () {
@@ -44,12 +41,12 @@ contract('ERC721Votes', function (accounts) {
 
   describe('transfers', function () {
     beforeEach(async function () {
-      await this.votes.mint(account1, this.NFT0);
+      await this.votes.mint(account1, this.token0);
     });
 
     it('no delegation', async function () {
-      const { receipt } = await this.votes.transferFrom(account1, account2, this.NFT0, { from: account1 });
-      expectEvent(receipt, 'Transfer', { from: account1, to: account2, tokenId: this.NFT0 });
+      const { receipt } = await this.votes.transferFrom(account1, account2, this.token0, { from: account1 });
+      expectEvent(receipt, 'Transfer', { from: account1, to: account2, tokenId: this.token0 });
       expectEvent.notEmitted(receipt, 'DelegateVotesChanged');
 
       this.account1Votes = '0';
@@ -59,8 +56,8 @@ contract('ERC721Votes', function (accounts) {
     it('sender delegation', async function () {
       await this.votes.delegate(account1, { from: account1 });
 
-      const { receipt } = await this.votes.transferFrom(account1, account2, this.NFT0, { from: account1 });
-      expectEvent(receipt, 'Transfer', { from: account1, to: account2, tokenId: this.NFT0 });
+      const { receipt } = await this.votes.transferFrom(account1, account2, this.token0, { from: account1 });
+      expectEvent(receipt, 'Transfer', { from: account1, to: account2, tokenId: this.token0 });
       expectEvent(receipt, 'DelegateVotesChanged', { delegate: account1, previousBalance: '1', newBalance: '0' });
 
       const { logIndex: transferLogIndex } = receipt.logs.find(({ event }) => event == 'Transfer');
@@ -73,8 +70,8 @@ contract('ERC721Votes', function (accounts) {
     it('receiver delegation', async function () {
       await this.votes.delegate(account2, { from: account2 });
 
-      const { receipt } = await this.votes.transferFrom(account1, account2, this.NFT0, { from: account1 });
-      expectEvent(receipt, 'Transfer', { from: account1, to: account2, tokenId: this.NFT0 });
+      const { receipt } = await this.votes.transferFrom(account1, account2, this.token0, { from: account1 });
+      expectEvent(receipt, 'Transfer', { from: account1, to: account2, tokenId: this.token0 });
       expectEvent(receipt, 'DelegateVotesChanged', { delegate: account2, previousBalance: '0', newBalance: '1' });
 
       const { logIndex: transferLogIndex } = receipt.logs.find(({ event }) => event == 'Transfer');
@@ -88,8 +85,8 @@ contract('ERC721Votes', function (accounts) {
       await this.votes.delegate(account1, { from: account1 });
       await this.votes.delegate(account2, { from: account2 });
 
-      const { receipt } = await this.votes.transferFrom(account1, account2, this.NFT0, { from: account1 });
-      expectEvent(receipt, 'Transfer', { from: account1, to: account2, tokenId: this.NFT0 });
+      const { receipt } = await this.votes.transferFrom(account1, account2, this.token0, { from: account1 });
+      expectEvent(receipt, 'Transfer', { from: account1, to: account2, tokenId: this.token0 });
       expectEvent(receipt, 'DelegateVotesChanged', { delegate: account1, previousBalance: '1', newBalance: '0'});
       expectEvent(receipt, 'DelegateVotesChanged', { delegate: account2, previousBalance: '0', newBalance: '1' });
 
@@ -103,7 +100,7 @@ contract('ERC721Votes', function (accounts) {
     it('returns the same total supply on transfers', async function () {
       await this.votes.delegate(account1, { from: account1 });
 
-      const { receipt } = await this.votes.transferFrom(account1, account2, this.NFT0, { from: account1 });
+      const { receipt } = await this.votes.transferFrom(account1, account2, this.token0, { from: account1 });
 
       await time.advanceBlock();
       await time.advanceBlock();
@@ -116,22 +113,22 @@ contract('ERC721Votes', function (accounts) {
     });
 
     it('generally returns the voting balance at the appropriate checkpoint', async function () {
-      await this.votes.mint(account1, this.NFT1);
-      await this.votes.mint(account1, this.NFT2);
-      await this.votes.mint(account1, this.NFT3);
+      await this.votes.mint(account1, this.token1);
+      await this.votes.mint(account1, this.token2);
+      await this.votes.mint(account1, this.token3);
 
       const total = await this.votes.balanceOf(account1);
 
       const t1 = await this.votes.delegate(other1, { from: account1 });
       await time.advanceBlock();
       await time.advanceBlock();
-      const t2 = await this.votes.transferFrom(account1, other2, this.NFT0, { from: account1 });
+      const t2 = await this.votes.transferFrom(account1, other2, this.token0, { from: account1 });
       await time.advanceBlock();
       await time.advanceBlock();
-      const t3 = await this.votes.transferFrom(account1, other2, this.NFT2, { from: account1 });
+      const t3 = await this.votes.transferFrom(account1, other2, this.token2, { from: account1 });
       await time.advanceBlock();
       await time.advanceBlock();
-      const t4 = await this.votes.transferFrom(other2, account1, this.NFT2, { from: other2 });
+      const t4 = await this.votes.transferFrom(other2, account1, this.token2, { from: other2 });
       await time.advanceBlock();
       await time.advanceBlock();
 

test/utils/Nonces.test.js

@@ -0,0 +1,25 @@
+require('@openzeppelin/test-helpers');
+
+const NoncesImpl = artifacts.require('NoncesImpl');
+
+contract('Nonces', function (accounts) {
+  const [ sender, other ] = accounts;
+
+  beforeEach(async function () {
+    this.nonces = await NoncesImpl.new();
+  });
+
+  it('gets a nonce', async function () {
+    expect(await this.nonces.nonces(sender)).to.be.bignumber.equal('0');
+  });
+
+  it('increment a nonce', async function () {
+    await this.nonces.useNonce(sender);
+    expect(await this.nonces.nonces(sender)).to.be.bignumber.equal('1');
+  });
+
+  it('nonce is specific to address argument', async function () {
+    await this.nonces.useNonce(sender);
+    expect(await this.nonces.nonces(other)).to.be.bignumber.equal('0');
+  });
+});