Mocking setImmediate by default breaks Co

[moll]

This is the corollary to tj/co#139:

I'm not sure who's problem this is, but Co v3.1.0 breaks when Sinon's fake timers are enabled, whereas v3.0.6 doesn't.

I found this when using co-mocha with Sinon and the following before blocks:

beforeEach(function() { this.time = Sinon.useFakeTimers(+NOON) })
afterEach(function() { this.time.restore() })

Now that generators with Co are used so liberally, this might require a better default.

[mroderick]

Just like @jonathanong asked for in the tj/co#139 issue, it would be greatly beneficial if you could provide a runnable test case that shows the issue.

[moll]

Kay, fair enough. I thought the report above was explanatory and obvious, but to speed things up:

package.json:

{
        "dependencies": {
                "mocha": ">= 1.18.2 < 2",
                "co": ">= 3.1.0 < 4",
                "sinon": ">= 1.9.1 < 2"
        }
}

index.js:

var Sinon = require("sinon")
var co = require("co")
var NOON = new Date(2000, 0, 1, 12)

describe("Test with Sinon and Co", function() {
        beforeEach(function() { this.time = Sinon.useFakeTimers(+NOON) })
        afterEach(function() { this.time.restore() })
        it("must not timeout", co(function*() {}))
})

Run it with:

./node_modules/.bin/mocha --harmony-generators index.js

Observe:

  1) Test with Sinon and Co must not timeout:
     Error: timeout of 2000ms exceeded

[cjohansen]

sinon.useFakeTimers(now, "setTimeout", "clearTimeout");

You can name the functions you want to fake - the default is all of 'em.

[moll]

Thanks. I was actually aware of this, that's why I added the last the bit at the end of "Now that generators with Co are used so liberally, this might require a better default.".

As @yanickrochon pointed out, and I agree, that setImmediate is more an event queue function than a timing function. You wouldn't mock process.nextTick by default would you? setImmediate in Node-land could be considered a synonym for that.

[mantoni]

Actually, I would prefer mocking process.nextTick by default. In an ideal world, sinon could guarantee that there is no asynchronous execution based on timings. To me setImmediate is a timing function, but you express that you want the delay to be as small as possible.