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Pattermesh merged 1 commit into from
Jun 3, 2026
Merged

Add EIP-2612 permit fuzz coverage #43

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242 changes: 141 additions & 101 deletions forge-test/Stablecoin.t.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,13 @@ import "forge-std/Test.sol";
import "../contracts/Stablecoin.sol";

contract StablecoinTest is Test {
bytes32 private constant PERMIT_TYPEHASH = keccak256(
"Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)"
);
bytes32 private constant EIP712_DOMAIN_TYPEHASH = keccak256(
"EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"
);

Stablecoin public coin;
address public admin = address(1);
address public user1 = address(2);
Expand Down Expand Up @@ -146,6 +153,115 @@ contract StablecoinTest is Test {
assertEq(coin.balanceOf(user2), 500_000);
}

// ==================== Permit ====================

function testFuzz_permitSetsAllowanceAndIncrementsNonce(
uint256 ownerKey,
address spender,
uint256 value,
uint256 deadline
) public {
ownerKey = bound(ownerKey, 1, type(uint128).max);
value = bound(value, 0, type(uint128).max);
deadline = bound(deadline, block.timestamp, type(uint64).max);
address owner = vm.addr(ownerKey);

(uint8 v, bytes32 r, bytes32 s) = _signPermit(
ownerKey, owner, spender, value, coin.nonces(owner), deadline, coin.DOMAIN_SEPARATOR()
);

coin.permit(owner, spender, value, deadline, v, r, s);

assertEq(coin.allowance(owner, spender), value);
assertEq(coin.nonces(owner), 1);
}

function testFuzz_expiredPermitReverts(uint256 ownerKey, address spender, uint256 value)
public
{
ownerKey = bound(ownerKey, 1, type(uint128).max);
value = bound(value, 0, type(uint128).max);
vm.warp(10);
uint256 expiredDeadline = block.timestamp - 1;
address owner = vm.addr(ownerKey);

(uint8 v, bytes32 r, bytes32 s) = _signPermit(
ownerKey,
owner,
spender,
value,
coin.nonces(owner),
expiredDeadline,
coin.DOMAIN_SEPARATOR()
);

vm.expectRevert();
coin.permit(owner, spender, value, expiredDeadline, v, r, s);
}

function testFuzz_wrongChainPermitReverts(
uint256 ownerKey,
address spender,
uint256 value,
uint256 deadline
) public {
ownerKey = bound(ownerKey, 1, type(uint128).max);
value = bound(value, 0, type(uint128).max);
deadline = bound(deadline, block.timestamp, type(uint64).max);
address owner = vm.addr(ownerKey);
bytes32 wrongChainDomain = _domainSeparator(block.chainid + 1, address(coin));

(uint8 v, bytes32 r, bytes32 s) = _signPermit(
ownerKey, owner, spender, value, coin.nonces(owner), deadline, wrongChainDomain
);

vm.expectRevert();
coin.permit(owner, spender, value, deadline, v, r, s);
}

function testFuzz_wrongVerifyingContractPermitReverts(
uint256 ownerKey,
address spender,
uint256 value,
uint256 deadline,
address wrongContract
) public {
ownerKey = bound(ownerKey, 1, type(uint128).max);
value = bound(value, 0, type(uint128).max);
deadline = bound(deadline, block.timestamp, type(uint64).max);
vm.assume(wrongContract != address(coin));
address owner = vm.addr(ownerKey);
bytes32 wrongContractDomain = _domainSeparator(block.chainid, wrongContract);

(uint8 v, bytes32 r, bytes32 s) = _signPermit(
ownerKey, owner, spender, value, coin.nonces(owner), deadline, wrongContractDomain
);

vm.expectRevert();
coin.permit(owner, spender, value, deadline, v, r, s);
}

function testFuzz_permitReplayReverts(
uint256 ownerKey,
address spender,
uint256 value,
uint256 deadline
) public {
ownerKey = bound(ownerKey, 1, type(uint128).max);
value = bound(value, 0, type(uint128).max);
deadline = bound(deadline, block.timestamp, type(uint64).max);
address owner = vm.addr(ownerKey);

(uint8 v, bytes32 r, bytes32 s) = _signPermit(
ownerKey, owner, spender, value, coin.nonces(owner), deadline, coin.DOMAIN_SEPARATOR()
);

coin.permit(owner, spender, value, deadline, v, r, s);

vm.expectRevert();
coin.permit(owner, spender, value, deadline, v, r, s);
}

// ==================== Fuzz Tests ====================

function testFuzz_mintAnyAmount(uint256 amount) public {
Expand Down Expand Up @@ -197,111 +313,35 @@ contract StablecoinTest is Test {
assertEq(coin.balanceOf(user1) + coin.balanceOf(user2), amount);
}

// ==================== EIP-2612 Permit Tests ====================

function _deployCoinWithOwner() internal returns (Stablecoin c, address owner_, uint256 ownerKey_) {
ownerKey_ = 0x1234567890123456789012345678901234567890123456789012345678901234;
owner_ = vm.addr(ownerKey_);
vm.prank(owner_);
c = new Stablecoin("Test Stablecoin", "TSTBL", owner_);
vm.prank(owner_);
c.mint(owner_, 1_000_000 ether);
}

function testFuzz_permitValid(uint256 value, uint256 deadline) public {
(Stablecoin c, address owner_, uint256 ownerKey_) = _deployCoinWithOwner();
address spender_ = address(0x5678);
vm.assume(value > 0 && value <= 1_000_000 ether);
vm.assume(deadline > block.timestamp);

uint256 nonce = c.nonces(owner_);
bytes32 digest = keccak256(
abi.encodePacked(
"\x19\x01",
c.DOMAIN_SEPARATOR(),
keccak256(
abi.encode(
keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)"),
owner_,
spender_,
value,
nonce,
deadline
)
)
)
function _signPermit(
uint256 ownerKey,
address owner,
address spender,
uint256 value,
uint256 nonce,
uint256 deadline,
bytes32 domainSeparator
) internal pure returns (uint8 v, bytes32 r, bytes32 s) {
bytes32 structHash = keccak256(
abi.encode(PERMIT_TYPEHASH, owner, spender, value, nonce, deadline)
);

(uint8 v, bytes32 r, bytes32 s) = vm.sign(ownerKey_, digest);

vm.prank(spender_);
c.permit(owner_, spender_, value, deadline, v, r, s);

assertEq(c.allowance(owner_, spender_), value);
assertEq(c.nonces(owner_), nonce + 1);
bytes32 digest = keccak256(abi.encodePacked("\x19\x01", domainSeparator, structHash));
return vm.sign(ownerKey, digest);
}

function testFuzz_permitExpiredDeadlineReverts(uint256 value) public {
(Stablecoin c, address owner_, uint256 ownerKey_) = _deployCoinWithOwner();
address spender_ = address(0x5678);
vm.assume(value > 0 && value <= 1_000_000 ether);
uint256 deadline = block.timestamp - 1;

bytes32 digest = keccak256(
abi.encodePacked(
"\x19\x01",
c.DOMAIN_SEPARATOR(),
keccak256(
abi.encode(
keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)"),
owner_,
spender_,
value,
c.nonces(owner_),
deadline
)
)
function _domainSeparator(uint256 chainId, address verifyingContract)
internal
pure
returns (bytes32)
{
return keccak256(
abi.encode(
EIP712_DOMAIN_TYPEHASH,
keccak256(bytes("Test Stablecoin")),
keccak256(bytes("1")),
chainId,
verifyingContract
)
);

(uint8 v, bytes32 r, bytes32 s) = vm.sign(ownerKey_, digest);

vm.prank(spender_);
vm.expectRevert();
c.permit(owner_, spender_, value, deadline, v, r, s);
}


function testFuzz_permitReplayReverts(uint256 value, uint256 deadline) public {
(Stablecoin c, address owner_, uint256 ownerKey_) = _deployCoinWithOwner();
address spender_ = address(0x5678);
vm.assume(value > 0 && value <= 1_000_000 ether);
vm.assume(deadline > block.timestamp);

bytes32 digest = keccak256(
abi.encodePacked(
"\x19\x01",
c.DOMAIN_SEPARATOR(),
keccak256(
abi.encode(
keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)"),
owner_,
spender_,
value,
c.nonces(owner_),
deadline
)
)
)
);

(uint8 v, bytes32 r, bytes32 s) = vm.sign(ownerKey_, digest);

vm.prank(spender_);
c.permit(owner_, spender_, value, deadline, v, r, s);

vm.prank(spender_);
vm.expectRevert();
c.permit(owner_, spender_, value, deadline, v, r, s);
}
}
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