test_erc20.sol

test_erc20.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

interface IERC20 {
    function symbol() external view returns (string memory);

    function name() external view returns (string memory);

    function decimals() external view returns (uint8);

    function totalSupply() external view returns (uint256);

    function balanceOf(address tokenOwner)
        external
        view
        returns (uint256 balance);

    function allowance(address tokenOwner, address spender)
        external
        view
        returns (uint256 remaining);

    function transfer(address to, uint256 tokens)
        external
        returns (bool success);

    function approve(address spender, uint256 tokens)
        external
        returns (bool success);

    function transferFrom(
        address from,
        address to,
        uint256 tokens
    ) external returns (bool success);

    event Transfer(address indexed from, address indexed to, uint256 tokens);
    event Approval(
        address indexed tokenOwner,
        address indexed spender,
        uint256 tokens
    );
}

contract ERC20 is IERC20 {
    string public constant override symbol = "ERC20";
    string public constant override name = "ERC20 TOKEN EXAMPLE";
    uint8 public constant override decimals = 18;
    uint256 public constant override totalSupply = 1000000 * 10**18;

    mapping(address => uint256) balances;
    mapping(address => mapping(address => uint256)) allowed;

    constructor() {
        balances[msg.sender] = totalSupply;
        emit Transfer(address(0), msg.sender, totalSupply);
    }

    function balanceOf(address tokenOwner)
        public
        view
        override
        returns (uint256 balance)
    {
        return balances[tokenOwner];
    }

    function transfer(address to, uint256 tokens)
        public
        override
        returns (bool success)
    {
        balances[msg.sender] -= tokens;
        balances[to] += tokens;
        emit Transfer(msg.sender, to, tokens);
        return true;
    }

    function approve(address spender, uint256 tokens)
        public
        override
        returns (bool success)
    {
        allowed[msg.sender][spender] = tokens;
        emit Approval(msg.sender, spender, tokens);
        return true;
    }

    function transferFrom(
        address from,
        address to,
        uint256 tokens
    ) public override returns (bool success) {
        balances[from] -= tokens;
        allowed[from][msg.sender] -= tokens;
        balances[to] += tokens;
        emit Transfer(from, to, tokens);
        return true;
    }

    function allowance(address tokenOwner, address spender)
        public
        view
        override
        returns (uint256 remaining)
    {
        return allowed[tokenOwner][spender];
    }
}