Stubs should have a resolves and rejects for setting promise results

[mariusGundersen]

This is very simple syntax sugar:

var stub = sinon.stub();
stub.resolves("hello");
//is the same as
stub.returns(Promise.resolve("hello"));

stub.rejects(new Error("oh noes!"));
//is the same as
stub.returns(Promise.reject(new Error("oh noes!"));

[mroderick]

That would be some nice sugar, thank you for the suggestion @mariusGundersen

[mkornblum]

Our team has a little library on npm which has been helping us with this kind of thing - https://github.com/substantial/sinon-stub-promise - although the way it's presently implemented it requires stub syntax like: sinon.stub().returnsPromise(). Thoughts? It looks like from the example above that this assumes synchronous evaluation, right?

[cjohansen]

I really like @mariusGundersen's suggestion. As far as I know, all promise libraries are async all the time, right? If so I think the stub promise should mirror this behavior.

[mariusGundersen]

I just figured it would use the globally available Promise.resolve, if one exists, and if not it wouldn't work. But letting it return an object with a then method is a much better solution:

var stub = sinon.stub(); 
stub.resolves("hello"); 
//is the same as 
stub.returns({then: x => setTimeout(()  => x("hello"), 0)}); 
stub.rejects(new Error("oh noes!")); 
//is the same as 
stub.returns({then: x => undefined, catch: x => setTimeout(() => x(new Error("oh noes!")), 0)});

(written on phone, might have errors)

[toddbluhm]

Our team wrote a little lib to provide similar functionality. Maybe this will help. It uses the bluebird library for promises. https://www.npmjs.com/package/sinon-bluebird

[screendriver]

+1 for native Promise support

[achingbrain]

There's also a project called sinon-as-promised which patches your project's existing sinon module using native-promise-only to add resolves/rejects semantics to stubs.

It'd be ace if this or the changes from one of the other modules could be added to sinon itself.

[jnystrom]

Can I do a sinon.stub().returnsArg(1) where the stub returns a promise? I am trying to just return the argument as the resolve of my promise. Does not seem to work.

[fatso83]

@jnystrom usage questions belong on the mailing list, but this is not something sinon currently supports as syntactic sugar. Perhaps you could suggest a syntax? Something like this should do what you want, and you don't need sinon for it.

stub = (arg) => Promise.resolve(arg);

[otroboe]

Same from here: #738

[lucasfcosta]

Hello everyone, first of all, thanks for the excellent work you guys have been doing on Sinon.
If you'd like to have this implemented I'd also love to give it a shot, just let me know and I'll start working at a PR for that.

[fatso83]

@lucasfcosta, thanks for that. I think @mroderick talked long ago about just integrating sinon-as-promised into Sinon, wasn't that so? That would be the easiest solution, and I have no objections.

[mroderick]

@lucasfcosta I would love to see a PR to integrate sinon-as-promised into Sinon's master branch