来, 抄作业
const allowance = await token_contract.allowance(c.caller, contract.address);
const allowance_dex = hre.ethers.utils.formatUnits(allowance, decimals);
if (allowance_dex < totalAmount) {
await token_contract.approve(contract.address, hre.ethers.utils.parseUnits('' + APPROVE_TOKEN_AMOUNT, decimals));
}