如何用 sinon 监视由 EventEmitter 事件触发的回调调用？ Javascript，ES6，单元测试，Chai答案

【问题标题】：How to spy with sinon on callback calls triggered by EventEmitter events? Javascript, ES6, Unit-tests, Chai如何用 sinon 监视由 EventEmitter 事件触发的回调调用？ Javascript，ES6，单元测试，Chai
【发布时间】：2018-11-28 03:49:31
【问题描述】：

我需要测试我的回调是否被调用了 n 次并且总是返回 true。
这是我在打字稿中的测试回调函数：

const checkBlockTransaction = (block: ILogsBlock) => {
  const tx = transactions.find(element => element.block === block.blockNumber);
  try {
    assert.strictEqual(block.transactions[0].amount, tx.amount);
  } catch (e) {
    return false;
  }
  return true;
};

这是我目前失败的测试，因为间谍没有注册任何函数调用

describe('Erc20DepositsWatcher', () => {
  it('handles blocks correctly', async () => {
    const spy = sinon.spy(checkBlockTransaction);
    for (const tx of transactions) {
      await deployedContract.methods.transfer(tx.address, tx.amount)
      .send({ from: addresses[0] });
    }

    depositsWatcher.subscribe(checkBlockTransaction);
    await depositsWatcher.startBroadcasting();
    await depositsWatcher.handleNewBlock(await web3.eth.getBlock('latest'));
    assert.equal(spy.callCount, 7);
    //sinon.assert.callCount(spy, 7);
    //assert(spy.alwaysReturned(true));
  });
});

也许有比用 sinon 监视更好的解决方案，但我还没找到

【问题讨论】：

标签： javascript ecmascript-6 sinon chai spy

【解决方案1】：

我目前的解决方案是没有间谍，但看起来不是很好：

function checkCallbackCalled(done: any, callsNumber: number) {
  let counter = 0;
  return (block: ILogsBlock) => {
    const tx = transactions.find(element => element.block === block.blockNumber);
    try {
      assert.strictEqual(block.transactions[0].amount, tx.amount);
    } catch (e) {
      done(e);
    }
    counter += 1;
    if (counter === callsNumber) done();
  };
}

describe('Erc20DepositsWatcher', () => {
  it('handles blocks correctly', async (done) => {
    for (const tx of transactions) {
      await deployedContract.methods.transfer(tx.address, tx.amount)
      .send({ from: addresses[0] });
    }

    depositsWatcher.subscribe(checkCallbackCalled(done, 7));
    await depositsWatcher.startBroadcasting();
    await depositsWatcher.handleNewBlock(await web3.eth.getBlock('latest'));
  });
});

【讨论】：