function testKeccak() public /**bytes memory data*/ {
   _testKeccak(hex"abcd");
   _testKeccak(hex"abcdef1234567890abcdef1234567890abcdef1234567890abcdef1234567890");
   _testKeccak("");
}

function _testKeccak(bytes memory data) internal {
   bytes32 expectedHash = keccak256(abi.encode(data));

   (bool success, bytes memory res) = keccak.call(abi.encode(data));
   require(success, "call failed");
   assertEq(
      expectedHash,
      abi.decode(res, (bytes32)),
      "huff keccak hash != expectedHash"
   );
}