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import { ethers } from "hardhat"; describe("VendingMachine", function () { // We define a fixture to reuse the same setup in every test. // We use loadFixture to run this setup once, snapshot that state, // and reset Hardhat Network to that snapshot in every test. async function VendingMachineFixture() { // Contracts are deployed using the first signer/account by default const [owner, otherAccou..

import { ethers } from "hardhat"; async function main() { console.log('deploying vendingMachine contract') const VendingMachine = await ethers.getContractFactory("VendingMachine"); const vendingMachine = await VendingMachine.deploy(); await vendingMachine.deployed(); console.log(`vendingMachine contract is deployed to ${vendingMachine.address}`); } // We recommend this pattern to be able to use ..

The error message invalid opcode: PUSH0 means that the Ethereum Virtual Machine (EVM) does not recognize the PUSH0 opcode. This opcode was introduced in Solidity compiler version 0.8.20, but it is not yet supported by all EVM implementations. If you are trying to deploy a contract that uses the PUSH0 opcode, you will need to make sure that you are deploying it to an EVM implementation that suppo..

// SPDX-License-Identifier: MIT pragma solidity >= 0.7.0 금액 mapping (address => uint) public balance; event log(bytes data); function deposit() public payable returns (uint) { balance[msg.sender] += msg.value; return msg.value; } function withdrawByCall(address payable _addr, uint _amount) public { require(balance[msg.sender] > _amount, "Insufficient Balanc..

The main difference between fallback() and receive() in Solidity is that fallback() is called when a contract receives Ether without any calldata, while receive() is called when a contract receives Ether with empty calldata. In other words, fallback() is called when a user sends Ether to a contract directly, while receive() is called when a user calls a function on a contract without passing any..

The receive() function in Solidity is a special function that is called automatically when a contract receives Ether without any calldata. This can happen when Ether is sent to the contract using the transfer() function or when a user sends Ether to the contract directly. The receive() function cannot have any arguments or return a value. It can only contain code that interacts with the contract..

The main difference between call() and delegatecall() in Solidity is that call() executes code in a new context, while delegatecall() executes code in the context of the caller. call() When you call a function using call(), the called function is executed in a new context, with its own stack and storage. This means that the called function does not have access to the caller's state, and any chan..

Delegatecall is a low-level Solidity opcode that allows a contract to execute code from another contract while using the state and storage of the calling contract. This can be used to implement a variety of features, such as: Upgrading contracts without losing data: Delegatecall can be used to upgrade a contract to a new version without losing any of the data stored in the contract. This is done..

The call() function in Solidity is a low-level function that can be used to call functions on other contracts or to send Ether to other addresses. It is a very powerful function, but it can also be dangerous if used incorrectly. The call() function takes two arguments: the address of the contract to call and the calldata to send to the function. The calldata is a byte array that contains the fun..

The transfer() function in Solidity is used to transfer Ether to an address. It takes two arguments: the address to transfer the Ether to and the amount of Ether to transfer. The transfer() function returns a boolean value indicating whether the transfer was successful. If the transfer was successful, the function returns true. If the transfer was unsuccessful, the function throws an exception a..