In JavaScript, however, you don’t have to do as much explicit decoupling to arrive at a flexible design. Consider the global property ‘Speaker’ to be the hook for plugging in your actual speaker implementation; I think of this as implicit decoupling.

That said, I do think that most JavaScript code out there could arguably need more explicit decoupling and explicit dependencies. My example tried to mimic the way in which many of the existing libraries are coded. So, maybe you are right and I shouldn’t fall into JavaScript’s everything-is-public-trap.

Therefore I would modify the Java-Script-Code to make it mockable more easily. And that would mean to inject a Speaker object to the DoubleSpeaker object. Then you don’t have to clean up the mess at the end of your test.

Having said that: A mock framework may be useful although. You may have to write too much test code even when you modify the testet code. But I haven’t an example at hand.