promise delay in mocha - promise

Question

I am learning sinon currently. My codes:
const bluebird = require('bluebird');
const sinon = require('sinon');
const sinonTest = require('sinon-test')(sinon);
sinon.test = sinonTest;
describe('xxx', function _test() {
this.timeout(2000);
it('should', sinon.test(function() {
return new bluebird.Promise( (resolve, reject) => {
try {
console.log('123');
resolve();
} catch ( err ) {
reject(err);
};
})
.then( () => console.log('456') )
.delay(100)
.then( () => console.log('789') )
.then(function() {
})
}));
});
output:
xxx
123
456
Why the above code times out and stuck in delay? Thanks
UPDATE
const bluebird = require('bluebird');
const sinon = require('sinon');
const sinonTest = require('sinon-test')(sinon);
sinon.test = sinonTest;
describe('xxx', function _test() {
this.timeout(2000);
it('should', sinon.test(function() {
return bluebird
.delay(100)
.then( () => console.log('789') );
}));
});
Output:
Error: Timeout of 2000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves
UPDATE
Thanks #Louis. Setting useFakeTimers works fine.
But I am just confused. Why in my project, there are no problems with the existing tests where useFakeTimers set to true by default? If useFakeTimers set true, promise delay cannot be used in sinonTest()?
By the way, I had this problem when upgrading sinon from 1.17.6 to 2.4.1.
Thanks

Answer 1

By default the sandboxes that Sinon creates have their configuration set so that the sandbox configuration option useFakeTimers is true. (Search for defaultConfig in this documentation page.)
This means that while the sandbox is in effect, the clock appears to be stopped, and Bluebird's delay never resolves. You tell sinon-test to create sandboxes without fake timers by passing a 2nd parameter when you configure it. This 2nd parameter is actually a configuration object for Sinon sandboxes:
const sinonTest = require('sinon-test')(sinon,
{ useFakeTimers: false });
I have not tried it, but from eyeballing the code, it looks like you could use multiple configurations at the same time if you need some tests to use fake timers and some to not use fake timers:
const sinonTest = require('sinon-test');
const wrapper = sinonTest(sinon, { useFakeTimers: false });
const wrapperWithTimers = sinonTest(sinon);
You just need to use the right wrapper for the needs of the test.
You added the question:
But I am just confused. Why in my project, there are no problems with the existing tests where useFakeTimers set to true by default? If useFakeTimers set true, promise delay cannot be used in sinonTest()?
By default useFakeTimers is true, but that won't cause a problem unless you have code that depends on the clock moving forward to work properly. I have many test suites where I use sandboxes and where I did not take care to turn off the fake timers and they work fine. Fake timers do not generally prevent asynchronous functions from running. If you do fs.readFile while the sandbox is in effect, for instance, it should work just fine. It just affects functions that depend on the clock, like setTimeout, setInterval and Date.
Bluebird's delay method is affected because it calls setTimeout.