很难用Javascript进行Truffle测试

Question

我已经开始对我的合同进行测试(使用Javascript)。我对特弗莱和摩卡都很陌生，虽然我一直在努力学习教程，但我很难准确地了解每一步发生的事情。例如，下面的测试代码主要是工作的，但是我在测试第27行中得到了一个错误：

whiteListLength = meta.getWhiteListLength.call();

带有错误消息：“无法读取属性”调用“未定义”。完整的测试在这里：

it("should add the correct account to the whitelist", function(){
  var account_one = accounts[0];
  var whiteListLength;
  var isAccountWhiteListed;
  var meta;

  return EMBallot.deployed().then(function(instance) { 
      meta = instance;
  return meta.addToWhiteList.call(account_one);
 })

.then(function(){
 whiteListLength = meta.getWhiteListLength.call();//this line is the problem
 return meta.amIWhitelisted.call(account_one); 
})

.then(function(response) {
  isAccountWhiteListed = response;

  assert.equal(whiteListLength, 1, "Whitelist should have exactly one member");
  assert.isTrue(isAccountWhiteListed);
 //here comes the assertions
});

对于具有代码的合同：

pragma solidity ^0.4.19;

contract EMBallot {

address[] whiteList;
 struct Proposal {
    uint voteCount;//how many votes this proposal has received
    string description;//what this option is about, what you are voting for
}
 struct Voter {
    bool voted;//if true, has already voted and any further attempts to vote are automatically ignored
    uint8 vote;
    string name;
}
Proposal[] proposals;  

address admin; //there should only be one admin per election, this variable stores the address designated as the admin.    
mapping(address => Voter) voters;//this creates a key-value pair, where addresses are the keys, 
and Voter structs(objects) are the values. 

function EMBallot() public{
admin = msg.sender;
}

function getWhiteListLength() constant returns(uint256){
    return whiteList.length;
}

function amIWhitelisted(address myAddress) constant returns(bool){
for(uint i=0; i<=whiteList.length; i++){//iterate over whiteList
if(myAddress == whiteList[i]){//i checked, you CAN use == on addresses
return true;
break;
}
return false;
}}

function addToWhiteList (address voter){
whiteList.push(voter);   
}
}

出于可读性的考虑，有些代码被故意省略，但这些函数是本测试中唯一相关的函数。

很抱歉，如果这暴露了缺乏理解的本质，但谁能向我解释为什么会发生这些失败呢？谢谢。

Answer 1

从格式上看，这有点困难，但看起来变量meta可能超出了作用域，因此显示为未定义的变量。将meta的声明向上移动一个级别。

var meta;    
it("should add the correct account to the whitelist", function(){
...

或者，实例变量meta = instance;可能为null。你能用console.log(instance);检查一下吗？

Answer 2

您的.thens和断言在it()块之外。您希望完成合同事务和调用的顺序，然后按下断言，所有这些都在it中。

尝尝这个

var myContact;
var response1;
var response2;

it("should ...", function() {
  MyContract.deployed() // no return
  .then(function(instance) {
    myContract = instance;
    return myContract.doSomething()
  })
  .then(function(response) {
    response1 = response;
    return myContract.somethingElse()
  })
  .then(function(response) {
    response2 = response;
    assert.equal(response1.toString(10),2,"response1 should be 2");
    assert.strictEqual(response2,false,"response2 isn't false");
  });
}); // this closes the it() block

希望能帮上忙。