• 引入@openzeppelin/test-helpers

  const { ether, BN, expectRevert, expectEvent, constants, time, balance, send } = require('@openzeppelin/test-helpers');

npm install -g truffle-flattener

because some new features in solidity 0.8.x might go wrong by [email protected], so after installed, run code below again:

inpm nstall -g https://github.com/jplew/truffle-flattener

usage:

truffle-flattener ./contracts/MyContract.sol > ./flatten/MyContractFlatten.sol

and then put faltten code as single solidity file to bscscan