Allow making assertions on a sequence of calls

[electricmonk]

I'd like to propose a feature to support the following:

var visitor = sinon.spy();
[1,2].forEach(visitor);
expect(visitor).to.have.been.calledWith(1).then.calledWith(2).

If you're for it, I can try to contribute via PR

[domenic]

What Sinon assertion does this correspond to?

[electricmonk]

Sinon doesn't have this feature out of the box. Basically I'll be adding the then method, which would somehow iterate over spy.getCalls. Maybe each consecutive call to then will increment a flag, then I can do getCall(utils.flag('sinon-call-depth').getAndIncrement()) to get the next call on each then.

[domenic]

Since Sinon doesn't have this feature, Sinon Chai should not. You should just use a series of assertions, instead of inventing a DSL.

[electricmonk]

The series of assertions would look like this:

var visitor = sinon.spy();
[1,2].forEach(visitor);
expect(visitor.getCall(0).args[0]).to.equal(1);
expect(visitor.getCall(1).args[0]).to.equal(2);

which is much less readable and more error prone. The purpose of a matcher library like Chai is to abstract away such implementation details in favor of well-described expectations. Why should the fact that this feature doesn't correspond to a function of Sinon mean that Sinon-Chai shouldn't expose it?

[electricmonk]

For future reference, if anyone's interested, I ended up implementing this in a complementary plugin:
https://github.com/electricmonk/sinon-chai-in-order