[英]Async callback timeout when unit testing nested async function
I want to implement a function which hits some apis asynchronously and does some calculations.我想实现一个 function 异步命中一些 api 并进行一些计算。 However I would like to use promises (also because I thought its easy to write unit test for them)
但是我想使用承诺(也因为我认为为它们编写单元测试很容易)
This is the function I want to write.这是我要写的function。
const CalcFactory = (someApi1, someApi2, someApi3) =>
async function calculation(params){
return new Promise((res, rej) =>{
const data1 = someApi1.getData() // getData is async
someApi2.getData((err, data) =>{
if(err)
rej(err);
else
res();
});
});
}
The question now is how to test and mock this?现在的问题是如何测试和模拟这个? My first test is if all the api methods are beeing called but I already struggle with that.
我的第一个测试是是否正在调用所有 api 方法,但我已经为此苦苦挣扎。
const Calculator = CalcFactory(api1Mock, api2Mock, api3Mock);
if('should hit all external apis', () => {
return Calculator(somedada).then(()=>{
expect(api1Mock.getData).toHaveBeenCalledWith(someData);
expect(api2Mock.getData).toHaveBeenCalledWith(somedata);
});
});
the mocks look like this:模拟看起来像这样:
const api1Mock = {
someData: jest.fn(),
}
const api2Mock = {
someData: jest.fn().mockResolvedValue({
data:{},
})
}
However I always get a timeout when I run the test.但是,当我运行测试时,我总是会超时。 I am also not really sure if this is a good approach to write the function but I really would like to use a promise.
我也不确定这是否是编写 function 的好方法,但我真的很想使用 promise。
There's getData
in one place and someData
in another.一个地方有
getData
,另一个地方有someData
。 Considering the promise is not rejected, it's not a problem.考虑到 promise 没有被拒绝,这不是问题。
Calculator(somedada)
promise isn't resolved because someApi2.getData
is incorrectly mocked and results in pending promise. Calculator(somedada)
promise 未解决,因为someApi2.getData
被错误地模拟并导致待处理的 promise。
It's an antipattern to return a promise from async
function without using await
.在不使用
await
的情况下从async
function 返回 promise 是一种反模式。 This means that either it doesn't benefit from being async
, or promise constructor contains too much besides promisfication of non-promise API.这意味着它要么不能从
async
中受益,要么 promise 构造函数除了承诺 API 之外包含太多内容。
In case the use of async
is justified, it can be:如果使用
async
是合理的,它可以是:
async function calculation(params){
...
const data1 = someApi1.getData()
const data2 = await new Promise((res, rej) =>{
someApi2.getData((err, data) => {
if(err)
rej(err);
else
res();
});
});
...
}
In Node, error-first callbacks can be promisified with util.promisify
.在 Node 中,可以使用
util.promisify
对错误优先回调进行承诺。
And mocked someApi2.getData
should use a callback like expected:并且嘲笑
someApi2.getData
应该使用像预期的回调:
const api2Mock = {
getData: jest.fn().mockImplementation(cb => cb(null, 'data'))
}
If someApi2.getData
is used more than once, it makes sense to promisify it instead of using promise constructor every time.如果
someApi2.getData
被多次使用,那么承诺它而不是每次都使用 promise 构造函数是有意义的。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.