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ballot.sol

pragma solidity ^0.4.17;

contract Lottery {
  address public manager;
  address[] public players;
  uint minEntry = .01 ether;
  uint managerFee = .01 ether;

  constructor() public {
    manager = msg.sender;
  }
  
  modifier restricted() {
    require(msg.sender == manager, "You're not the manager!");
      _;
  }

  function enter() public payable {
    require(msg.value > minEntry, "The minimum entry is .01 ETH");

    players.push(msg.sender);
  }

  function pickWinner() public restricted {
    require(players.length > 1, "Not enough players!");
    require(address(this).balance > 0, "There is no prize to distribute");

    uint winnerIndex = _random(players.length);
    address winner = players[winnerIndex];

    // Reset the players list
    players = new address[](0);
    
    // Calculate & transfer the prize
    manager.transfer(managerFee);
    winner.transfer(address(this).balance);
  }

  function _random(uint limit) private view returns (uint) {
    assert(limit > 0);
    bytes memory input = abi.encodePacked(block.difficulty, now, players);
    return uint(keccak256(input)) % limit;
  }
}

ballot_test.sol

pragma solidity ^0.4.7;
import "remix_tests.sol"; // this import is automatically injected by Remix.
import "./ballot.sol";

contract test3 {
   
    Ballot ballotToTest;
    function beforeAll () {
       ballotToTest = new Ballot(2);
    }
    
    function checkWinningProposal () public {
        ballotToTest.vote(1);
        Assert.equal(ballotToTest.winningProposal(), uint(1), "1 should be the winning proposal");
    }
    
    function checkWinninProposalWithReturnValue () public constant returns (bool) {
        return ballotToTest.winningProposal() == 1;
    }
}