javascript - 在 mocha 中断言函数失败 "assert"导致超时而不是失败

Question

我有以下测试:

it ('clears the many cache when a new document is inserted', () => {

return new Promise(async(resolve) => {
    const entity = new Entity(connector, collectionName);
    entity.insert({_id: '2'});
    result = await entity.findManyCached();

    // this assert does not fail the test, but makes the case time out
    assert.deepEqual(result, [{_id: 1}]);
  })
})

如何收集失败断言的结果而不是超时？

Answer 1

我认为发生的事情是，由于使 promise 的执行程序函数异步，您将得到与此等效的内容:

return new Promise(outerResolve => {
  return new Promise(innerResolve => {
    ...
    assert.deepEqual(...);
  })
})

assert 抛出的任何异常都会被内部 promise 吞没，并且外部 promise 永远不会被解决或被拒绝，因此超时。

独立演示:

let p = new Promise(outerResolve => {
  console.log('outer promise');
  return new Promise(innerResolve => {
    console.log('inner promise');
    throw Error('foo');
  })
})

// This doesn't log anything:    
p.then (x => console.log('resolved'))
 .catch(e => console.log('rejected'));

解决方法如下:

it ('clears the many cache when a new document is inserted', async () => {
  const entity = new Entity(connector, collectionName);
  entity.insert({_id: '2'});
  let result = await entity.findManyCached();

  // this assert does not fail the test, but makes the case time out
  assert.deepEqual(result, [{_id: 1}]);
})