Created using remix-ide: Realtime Ethereum Contract Compiler and Runtime. Load this file by pasting this gists URL or ID at https://remix.ethereum.org/#version=soljson-v0.5.2+commit.1df8f40c.js&optimize=false&gist=

ERC20.sol

pragma solidity ^0.5.0;

import "./IERC20.sol";
import "./SafeMath.sol";

/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md
 * Originally based on code by FirstBlood:
 * https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
 *
 * This implementation emits additional Approval events, allowing applications to reconstruct the allowance status for
 * all accounts just by listening to said events. Note that this isn't required by the specification, and other
 * compliant implementations may not do it.
 */
contract ERC20 is IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowed;

    uint256 private _totalSupply;

    /**
    * @dev Total number of tokens in existence
    */
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    /**
    * @dev Gets the balance of the specified address.
    * @param owner The address to query the balance of.
    * @return An uint256 representing the amount owned by the passed address.
    */
    function balanceOf(address owner) public view returns (uint256) {
        return _balances[owner];
    }

    /**
     * @dev Function to check the amount of tokens that an owner allowed to a spender.
     * @param owner address The address which owns the funds.
     * @param spender address The address which will spend the funds.
     * @return A uint256 specifying the amount of tokens still available for the spender.
     */
    function allowance(address owner, address spender) public view returns (uint256) {
        return _allowed[owner][spender];
    }

    /**
    * @dev Transfer token for a specified address
    * @param to The address to transfer to.
    * @param value The amount to be transferred.
    */
    function transfer(address to, uint256 value) public returns (bool) {
        _transfer(msg.sender, to, value);
        return true;
    }

    /**
     * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
     * Beware that changing an allowance with this method brings the risk that someone may use both the old
     * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
     * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     * @param spender The address which will spend the funds.
     * @param value The amount of tokens to be spent.
     */
    function approve(address spender, uint256 value) public returns (bool) {
        require(spender != address(0));

        _allowed[msg.sender][spender] = value;
        emit Approval(msg.sender, spender, value);
        return true;
    }

    /**
     * @dev Transfer tokens from one address to another.
     * Note that while this function emits an Approval event, this is not required as per the specification,
     * and other compliant implementations may not emit the event.
     * @param from address The address which you want to send tokens from
     * @param to address The address which you want to transfer to
     * @param value uint256 the amount of tokens to be transferred
     */
    function transferFrom(address from, address to, uint256 value) public returns (bool) {
        _allowed[from][msg.sender] = _allowed[from][msg.sender].sub(value);
        _transfer(from, to, value);
        emit Approval(from, msg.sender, _allowed[from][msg.sender]);
        return true;
    }

    /**
     * @dev Increase the amount of tokens that an owner allowed to a spender.
     * approve should be called when allowed_[_spender] == 0. To increment
     * allowed value is better to use this function to avoid 2 calls (and wait until
     * the first transaction is mined)
     * From MonolithDAO Token.sol
     * Emits an Approval event.
     * @param spender The address which will spend the funds.
     * @param addedValue The amount of tokens to increase the allowance by.
     */
    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        require(spender != address(0));

        _allowed[msg.sender][spender] = _allowed[msg.sender][spender].add(addedValue);
        emit Approval(msg.sender, spender, _allowed[msg.sender][spender]);
        return true;
    }

    /**
     * @dev Decrease the amount of tokens that an owner allowed to a spender.
     * approve should be called when allowed_[_spender] == 0. To decrement
     * allowed value is better to use this function to avoid 2 calls (and wait until
     * the first transaction is mined)
     * From MonolithDAO Token.sol
     * Emits an Approval event.
     * @param spender The address which will spend the funds.
     * @param subtractedValue The amount of tokens to decrease the allowance by.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
        require(spender != address(0));

        _allowed[msg.sender][spender] = _allowed[msg.sender][spender].sub(subtractedValue);
        emit Approval(msg.sender, spender, _allowed[msg.sender][spender]);
        return true;
    }

    /**
    * @dev Transfer token for a specified addresses
    * @param from The address to transfer from.
    * @param to The address to transfer to.
    * @param value The amount to be transferred.
    */
    function _transfer(address from, address to, uint256 value) internal {
        require(to != address(0));

        _balances[from] = _balances[from].sub(value);
        _balances[to] = _balances[to].add(value);
        emit Transfer(from, to, value);
    }

    /**
     * @dev Internal function that mints an amount of the token and assigns it to
     * an account. This encapsulates the modification of balances such that the
     * proper events are emitted.
     * @param account The account that will receive the created tokens.
     * @param value The amount that will be created.
     */
    function _mint(address account, uint256 value) internal {
        require(account != address(0));

        _totalSupply = _totalSupply.add(value);
        _balances[account] = _balances[account].add(value);
        emit Transfer(address(0), account, value);
    }
    
    constructor(address account) public {
        _mint(account, 1000);        
    }

    /**
     * @dev Internal function that burns an amount of the token of a given
     * account.
     * @param account The account whose tokens will be burnt.
     * @param value The amount that will be burnt.
     */
    function _burn(address account, uint256 value) internal {
        require(account != address(0));

        _totalSupply = _totalSupply.sub(value);
        _balances[account] = _balances[account].sub(value);
        emit Transfer(account, address(0), value);
    }

    /**
     * @dev Internal function that burns an amount of the token of a given
     * account, deducting from the sender's allowance for said account. Uses the
     * internal burn function.
     * Emits an Approval event (reflecting the reduced allowance).
     * @param account The account whose tokens will be burnt.
     * @param value The amount that will be burnt.
     */
    function _burnFrom(address account, uint256 value) internal {
        _allowed[account][msg.sender] = _allowed[account][msg.sender].sub(value);
        _burn(account, value);
        emit Approval(account, msg.sender, _allowed[account][msg.sender]);
    }
}

ERC20TokenValidator.sol

/*
    IERC20
    
    function totalSupply() external view returns (uint256);

    function balanceOf(address who) external view returns (uint256);

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

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

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

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

    event Transfer(address indexed from, address indexed to, uint256 value);

    event Approval(address indexed owner, address indexed spender, uint256 value);
*/

/* Instructions

    Create an ERC20 token conforming to the IERC20.sol interface, then transfer 1000 tokens to the level contract.
    A battery of tests will be run against your submitted token contract address to check that it behaves as expected
*/

// player should have transferred some tokens to validator contract (1000)?

// should return a totalSupply with x
// validator calls balanceOf with its own address
// validator calls balanceOf with another address that shouldn't have tokens
// validator transfers tokens from one address to another 
//   1. transfer works when sender has enough balance -> balanceOf should update correctly
//   2. transfer should fail when there is insufficient balance 
// 

pragma solidity ^0.5.0;

import "./IERC20.sol";

contract ERC20TokenValidator {
  bool public cleared = false;
  
  function submitContract(address answer) public {
    IERC20 token = IERC20(answer);
    
    require(testTotalSupply(token), 'Failed totalSupply check');
    require(testBalanceOf(token), 'Failed balanceOf check');
    
    
    cleared = true;
  }
  
  function testTotalSupply(IERC20 token) internal returns (bool) {
    return (token.totalSupply() == 1000);
  }
  
  function testBalanceOf(IERC20 token) internal returns (bool) {
      uint REQUIRED_TOKEN_VALUE = 1000;
      address anotherAccount = address(0xA12dEbD6a9D55B4eC58F614c993b94635cD8B87F); // random account address
      bool testBalanceOfAnotherAccount = (token.balanceOf(anotherAccount) == 0);
      bool testBalanceOfThisAccount = (token.balanceOf(address(this)) == REQUIRED_TOKEN_VALUE);
      
      return (testBalanceOfThisAccount && testBalanceOfAnotherAccount);
  }
  
  function testTransfer(IERC20 token) internal returns (bool) {
      
  }
  
  
  
  
}

Ethernaut.sol

pragma solidity ^0.5.0;

import "./levels/base/Level.sol";
import "./utils/Ownable.sol";
import "./ScoreTracker.sol";

contract Ethernaut is Ownable {
  struct EmittedInstanceData {
    address player;
    Level level;
    bool completed;
  }

  mapping(address => bool) public registeredLevels;
  mapping(address => EmittedInstanceData) public emittedInstances;
  ScoreTracker public scoreTracker;

  event LevelInstanceCreatedLog(address indexed player, address instance);
  event LevelCompletedLog(address indexed player, Level level);

  constructor(string memory _tokenName, string memory _tokenSymbol) public {
    scoreTracker = new ScoreTracker(_tokenName, _tokenSymbol);
  }

  function registerLevel(Level _level, uint256 _reward) public onlyOwner {
    registeredLevels[address(_level)] = true;
    scoreTracker.registerLevel(address(_level), _reward);
  }

  function createLevelInstance(Level _level) public payable {

    // Ensure level is registered.
    require(registeredLevels[address(_level)], "Level is not registered");

    // Get level factory to create an instance.
    address instance = _level.createInstance.value(msg.value)(msg.sender);

    // Store emitted instance relationship with player and level.
    emittedInstances[instance] = EmittedInstanceData(msg.sender, _level, false);

    // Retrieve created instance via logs.
    emit LevelInstanceCreatedLog(msg.sender, instance);
  }

  function submitLevelInstance(address _instance) public {

    // Get player and level.
    EmittedInstanceData storage data = emittedInstances[_instance];
    require(data.player == msg.sender, "Instance is not submitted by player"); // instance was emitted for this player
    require(data.completed == false, "Instance is not completed"); // not already submitted

    // Have the level check the instance.
    if(data.level.validateInstance(_instance, msg.sender)) {

      // Register instance as completed.
      data.completed = true;

      // Notify success via logs.
      emit LevelCompletedLog(msg.sender, data.level);

      // Notify score tracker of completed level
      scoreTracker.levelCompleted(msg.sender, address(data.level));
    }
  }
}

FizzBuzz.sol

pragma solidity ^0.5.2;

interface IFizzBuzz {
  function fizzBuzz(uint256 num) external pure returns (string memory);
}


contract FizzBuzz is IFizzBuzz {
  function fizzBuzz(uint256 num) external pure returns (string memory out) {
      if (num == 0) {
          return "0";
      }
    // append Fizz to output if multiple of 3
    if (num % 3 == 0) {
        out = "Fizz";
    }
    // append Buzz to output if multiple of 5
    if (num % 5 == 0) {
        out = strConcat(out, "Buzz");
    }
    // append number if nothing in output yet
    uint strLength = bytes(out).length;
    if (strLength == 0) {
        out = uint2str(num);
    }
    
    return out;
  }

    function uint2str(uint _i) internal pure returns (string memory _uintAsString) {
        if (_i == 0) {
            return "0";
        }
        uint j = _i;
        uint len;
        while (j != 0) {
            len++;
            j /= 10;
        }
        bytes memory bstr = new bytes(len);
        uint k = len - 1;
        while (_i != 0) {
            bstr[k--] = byte(uint8(48 + _i % 10));
            _i /= 10;
        }
        return string(bstr);
    }
    
    function strConcat(string memory _a, string memory _b) internal pure returns (string memory _concatenatedString) {
        return strConcat(_a, _b, "", "", "");
    }

    function strConcat(string memory _a, string memory _b, string memory _c) internal pure returns (string memory _concatenatedString) {
        return strConcat(_a, _b, _c, "", "");
    }

    function strConcat(string memory _a, string memory _b, string memory _c, string memory _d) internal pure returns (string memory _concatenatedString) {
        return strConcat(_a, _b, _c, _d, "");
    }

    function strConcat(string memory _a, string memory _b, string memory _c, string memory _d, string memory _e) internal pure returns (string memory _concatenatedString) {
        bytes memory _ba = bytes(_a);
        bytes memory _bb = bytes(_b);
        bytes memory _bc = bytes(_c);
        bytes memory _bd = bytes(_d);
        bytes memory _be = bytes(_e);
        string memory abcde = new string(_ba.length + _bb.length + _bc.length + _bd.length + _be.length);
        bytes memory babcde = bytes(abcde);
        uint k = 0;
        uint i = 0;
        for (i = 0; i < _ba.length; i++) {
            babcde[k++] = _ba[i];
        }
        for (i = 0; i < _bb.length; i++) {
            babcde[k++] = _bb[i];
        }
        for (i = 0; i < _bc.length; i++) {
            babcde[k++] = _bc[i];
        }
        for (i = 0; i < _bd.length; i++) {
            babcde[k++] = _bd[i];
        }
        for (i = 0; i < _be.length; i++) {
            babcde[k++] = _be[i];
        }
        return string(babcde);
    }

}

FizzBuzzValidator.sol

pragma solidity ^0.5.0;

import "./IFizzBuzz.sol";

contract FizzBuzzValidator {
  bool public cleared = false;
  
  function compareString(string memory s1, string memory s2) internal pure returns (bool){
    return keccak256(abi.encodePacked(s1)) == keccak256(abi.encodePacked(s2));
  }
  
  function submitContract(address answer) public {
    IFizzBuzz fizzBuzz = IFizzBuzz(answer);
    
    require(compareString(fizzBuzz.fizzBuzz(1), "1"), "fizzBuzz(1) failed");
    require(compareString(fizzBuzz.fizzBuzz(3), "Fizz"), "fizzBuzz(3) failed");
    require(compareString(fizzBuzz.fizzBuzz(5), "Buzz"), "fizzBuzz(5) failed");
    require(compareString(fizzBuzz.fizzBuzz(15), "FizzBuzz"), "fizzBuzz(15) failed");
    
    require(
      compareString(
        fizzBuzz.fizzBuzz(57896044618658097711785492504343953926634992332820282019728792003956564819960),
        "FizzBuzz"
      ),
      "fizzBuzz(57896044618658097711785492504343953926634992332820282019728792003956564819960) failed"
    );
    require(
      compareString(
        fizzBuzz.fizzBuzz(57896044618658097711785492504343953926634992332820282019728792003956564819961),
        "57896044618658097711785492504343953926634992332820282019728792003956564819961"
      ),
      "fizzBuzz(57896044618658097711785492504343953926634992332820282019728792003956564819961) failed"
    );
    require(
      compareString(
        fizzBuzz.fizzBuzz(57896044618658097711785492504343953926634992332820282019728792003956564819965),
        "Buzz"
      ),
      "fizzBuzz(57896044618658097711785492504343953926634992332820282019728792003956564819965) failed"
    );
    require(
      compareString(
        fizzBuzz.fizzBuzz(57896044618658097711785492504343953926634992332820282019728792003956564819966),
        "Fizz"
      ),
      "fizzBuzz(57896044618658097711785492504343953926634992332820282019728792003956564819966) failed"
    );
    
    cleared = true;
  }
}

FizzBuzzValidatorFactory.sol

pragma solidity ^0.5.0;

import "./Level.sol";
import "./FizzBuzzValidator.sol";

contract FizzBuzzValidatorFactory is Level {

  function createInstance(address _player) public payable returns (address) {
    _player;
    FizzBuzzValidator instance = new FizzBuzzValidator();
    return address(instance);
  }

  function validateInstance(address _instance, address _player) public returns (bool) {
    _player;
    FizzBuzzValidator instance = FizzBuzzValidator(_instance);
    return instance.cleared();
  }
}

IERC20.sol

pragma solidity ^0.5.0;

/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
interface IERC20 {
    function transfer(address to, uint256 value) external returns (bool);

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

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

    function totalSupply() external view returns (uint256);

    function balanceOf(address who) external view returns (uint256);

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

    event Transfer(address indexed from, address indexed to, uint256 value);

    event Approval(address indexed owner, address indexed spender, uint256 value);
}

IFizzBuzz.sol

pragma solidity ^0.5.0;

interface IFizzBuzz {
  function fizzBuzz(uint256 num) external pure returns (string memory);
}

Level.sol

pragma solidity ^0.5.0;

import "./Ownable.sol";

contract Level is Ownable {
  function createInstance(address _player) public payable returns (address);
  function validateInstance(address _instance, address _player) public returns (bool);
}

Ownable.sol

/* solium-disable error-reason*/
pragma solidity ^0.5.0;

/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 */
contract Ownable {
  address private _owner;

  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

  /**
   * @dev The Ownable constructor sets the original `owner` of the contract to the sender
   * account.
   */
  constructor () internal {
    _owner = msg.sender;
    emit OwnershipTransferred(address(0), _owner);
  }

  /**
   * @return the address of the owner.
   */
  function owner() public view returns (address) {
    return _owner;
  }

  /**
   * @dev Throws if called by any account other than the owner.
   */
  modifier onlyOwner() {
    require(isOwner());
    _;
  }

  /**
   * @return true if `msg.sender` is the owner of the contract.
   */
  function isOwner() public view returns (bool) {
    return msg.sender == _owner;
  }

  /**
   * @dev Allows the current owner to relinquish control of the contract.
   * @notice Renouncing to ownership will leave the contract without an owner.
   * It will not be possible to call the functions with the `onlyOwner`
   * modifier anymore.
   */
  function renounceOwnership() public onlyOwner {
    emit OwnershipTransferred(_owner, address(0));
    _owner = address(0);
  }

  /**
   * @dev Allows the current owner to transfer control of the contract to a newOwner.
   * @param newOwner The address to transfer ownership to.
   */
  function transferOwnership(address newOwner) public onlyOwner {
    _transferOwnership(newOwner);
  }

  /**
   * @dev Transfers control of the contract to a newOwner.
   * @param newOwner The address to transfer ownership to.
   */
  function _transferOwnership(address newOwner) internal {
    require(newOwner != address(0));
    emit OwnershipTransferred(_owner, newOwner);
    _owner = newOwner;
  }
}

SafeMath.sol

pragma solidity ^0.5.0;

/**
 * @title SafeMath
 * @dev Unsigned math operations with safety checks that revert on error
 */
library SafeMath {
    /**
    * @dev Multiplies two unsigned integers, reverts on overflow.
    */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b);

        return c;
    }

    /**
    * @dev Integer division of two unsigned integers truncating the quotient, reverts on division by zero.
    */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
    * @dev Subtracts two unsigned integers, reverts on overflow (i.e. if subtrahend is greater than minuend).
    */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a);
        uint256 c = a - b;

        return c;
    }

    /**
    * @dev Adds two unsigned integers, reverts on overflow.
    */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a);

        return c;
    }

    /**
    * @dev Divides two unsigned integers and returns the remainder (unsigned integer modulo),
    * reverts when dividing by zero.
    */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b != 0);
        return a % b;
    }
}

testingtests.sol

contract z {
    function o(address target) public returns (bool) {
        y(target).q();
        return true;
    }
    
    function h(address target) public returns (bool) {
        return y(target).p();
    }
}

contract y {
    function q() public returns (bool) {
        require(false);
    }
    
    function p() public returns (bool) {
        return true;
    }
}

contract x {
    function o(address target) public returns (bool) {
        y(target).q();
        return true;
    }
    
    function h(address target) public returns (bool) {
    y thrower = y(target);
    ThrowProxy throwProxyy = new ThrowProxy(target); //set Thrower as the contract to forward requests to. The target.

    //prime the proxy.
    y(address(throwProxyy)).p();
    //execute the call that is supposed to throw.
    //r will be false if it threw. r will be true if it didn't.
    //make sure you send enough gas for your contract method.
    bool r = throwProxyy.execute.gas(200000)();

    return r;
    }
}

// Proxy contract for testing throws
contract ThrowProxy {
  address public target;
  bytes data;

  constructor(address _target) public {
    target = _target;
  }

  //prime the data using the fallback function.
  function() external {
    data = msg.data;
  }

  function execute() public returns (bool res) {
    (res, ) = target.call(data);
    return res;
  }
}

throwproxy.sol

// Proxy contract for testing throws
contract ThrowProxy {
  address public target;
  bytes data;

  constructor(address _target) public {
    target = _target;
  }

  //prime the data using the fallback function.
  function() external {
    data = msg.data;
  }

  function execute() public returns (bool, bytes memory) {
      return target.call(data);
  }
}

// Contract you're testing
contract Thrower {
  function doThrow(uint a, uint b, uint c) public {
      if (a == 1) {
    revert();
      }
  }

  function doNoThrow() public {
    //
  }
}

// Solidity test contract, meant to test Thrower
contract TestThrower {
  function testThrow(address target, uint param) public returns (bool) {
    ThrowProxy throwProxy = new ThrowProxy(target); //set Thrower as the contract to forward requests to. The target.

    //prime the proxy.
    Thrower(address(throwProxy)).doThrow(param, 2, 3);
    //execute the call that is supposed to throw.
    //r will be false if it threw. r will be true if it didn't.
    //make sure you send enough gas for your contract method.
    (bool r, ) = throwProxy.execute.gas(200000)();

    return r;
  }
}