How to use Promises in Postman tests?

Question

I need to use some async code in my Postman test.

As it's a complex scenario I've reproduced the scenario in a very simple test with the following code:

let promiseNumber = 0;

function resolvedPromise() {
    return new Promise((resolve, reject) => {
        pm.sendRequest('https://postman-echo.com/get', (err, res) => {
            if (err) {
                console.log(err);
                reject();
            } else {
                console.log(`Resolved promise ${++promiseNumber}`);
                resolve();
            }
        });
    });
}

resolvedPromise()
    .then(resolvedPromise)
    .then(resolvedPromise)
    .catch(err => console.log(err));

The expected result on the console would be:

Resolved promise 1
Resolved promise 2
Resolved promise 3

But instead I receive:

Resolved promise 1

Is there a way to make Promises or async code available at Postman?

Answer 1

UPDATE: The original solution used 2147483647 as timeout value, now it was refactored to use Number.MAX_SAFE_INTEGER as suggested in the comments.

I did some more tests and realize that it always stop working after I use pm.sendRequest. If I try to resolve the Promise it works.

Seems a known bug looking at this thread.

The workaround for it would be only leave an open timeout while processing the code. Just ensure all possible paths clear the timeout or the call will hang for 300000 years 😀

// This timeout ensure that postman will not close the connection before completing async tasks.
//  - it must be cleared once all tasks are completed or it will hang
const interval = setTimeout(() => {}, Number.MAX_SAFE_INTEGER);

let promiseNumber = 0;

function resolvedPromise() {
    return new Promise((resolve, reject) => {
        pm.sendRequest('https://postman-echo.com/get', (err, res) => {
            if (err) {
                console.log(err);
                reject();
            } else {
                console.log(`Resolved promise ${++promiseNumber}`);
                resolve();
            }
        });
    });
}

resolvedPromise()
    .then(resolvedPromise)
    .then(resolvedPromise)
    .then(() => clearTimeout(interval))
    .catch(err => {
        console.log(err);
        clearTimeout(interval);
    });

Now it prints the expected result:

Resolved promise 1
Resolved promise 2
Resolved promise 3