msg.sender.transfer (KaufÜberschuss); Versagen im Festigkeitstest

Die Transaktion schlägt fehl, weil der Testvertrag keine kostenpflichtige Fallback-Funktion hat, um die überschüssigen Gelder „zu übertragen“.

pragma solidity ^0.4.17;

import "../contracts/EmojiCoin.sol"; 
import "truffle/Assert.sol";
import "truffle/DeployedAddresses.sol";

contract TestEmojiCoin {
    uint public initialBalance = 1 ether;

    function testPurchase() public {
        address contractAddress = DeployedAddresses.EmojiCoin();
        EmojiCoin emojiCoin = EmojiCoin(contractAddress);

        // Emoji 0 is created in previous test.

        address owner_0 = emojiCoin.tokenOwner(0);
        Assert.notEqual( owner_0, this, "owner for coin 0 is incorrect" );

        emojiCoin.purchase.value(1 ether).gas(30000000000)(0);

        owner_0 = emojiCoin.tokenOwner(0);
        Assert.equal( owner_0, this, "owner for coin 0 is incorrect" );
    }

    // this new function IS REQUIRED for the test to work
    function() public payable { }

}

Zwei Behauptungstests wurden hinzugefügt (einige könnten argumentieren, dass dies keine bewährte Methode ist, mehr als eine Behauptung im selben Test zu haben)

Außerdem musste ein sehr einfacher EmojiCoin-Vertrag implementiert werden, um zu überprüfen, ob dies das Problem war:

pragma solidity ^0.4.17;

import "zeppelin-solidity/contracts/math/SafeMath.sol";

contract EmojiCoin {

    mapping(uint256 => address) public tokenOwner;
    mapping(uint256 => uint256) public emojiIndexToPrice;
    uint256 public ownerCut  = 5;


    function EmojiCoin() public {

        // very simple constructor for the purpose of testing only
        tokenOwner[0] = msg.sender;
        emojiIndexToPrice[0] = 1 ether;

    }

    // simple _transfer implementation for the purpose of testing only
    function _transfer(address oldOwner, address newOwner, uint256 _tokenId) internal {
        require(tokenOwner[_tokenId] == oldOwner);
        tokenOwner[_tokenId] = newOwner;
    }

    function purchase(uint256 _tokenId) public payable {
        address oldOwner = tokenOwner[_tokenId];
        uint256 sellingPrice = emojiIndexToPrice[_tokenId];
        address newOwner = msg.sender;

        require(oldOwner != newOwner);

        require(newOwner != address(0));

        require(msg.value >= sellingPrice);

        uint256 percentage = SafeMath.sub(100, ownerCut);
        uint256 payment = uint256(SafeMath.div(SafeMath.mul(sellingPrice, percentage), 100));
        uint256 purchaseExcess = SafeMath.sub(msg.value, sellingPrice);

        emojiIndexToPrice[_tokenId] = SafeMath.div(SafeMath.mul(sellingPrice, 150), percentage);

        _transfer(oldOwner, newOwner, _tokenId);

        if (oldOwner != address(this)) {
           oldOwner.transfer(payment);
        }

        msg.sender.transfer(purchaseExcess);
    }


}