add QUnit deepEqual

[Krinkle]

Follows-up c0f8f22.

[Krinkle]

QUnit was originally developed by John Resig as part of jQuery. [...] QUnit's assertion methods follow the CommonJS Unit Testing specification, which was to some degree influenced by QUnit.

I can't believe this […] The docs also mention a complete re-write of QUnit […]

The original QUnit indeed used a plethora of global variables similar to Mocha and various other JS testing frameworks from that era. I believe the idea is that the testing framework would be given a dedicated web page (or Node.js process) with no other libraries present, where it then exports its functions as a way of almost augmenting the language syntax with additional operators.

The complete rewrite, as done by yours truly and team, deprecated these in QUnit 1.16, in favour of a more lexically bound API (QUnit 2.0).

Given this state of affairs, it is perhaps not so surprising that issue joyent/node#7161 prompted the suggestion to add deepStrictEqual […]

One gets the impression the CommonJS folks who wrote the unit testing specs must have started out, like, "wah equality, that's JS ==", and then at some point realized "cool, there's JS ===, let's add it, too".

A little later […] those folks went, like, "oh noes, we need deepEqual, let's add it already". Of course, since they started out with the broken JS == operator, they recycled that experience when implementing deepEqual, so now their deepEqual is as broken as their equal.

For what it's worth, the CommonJS spec actually describes === strict equality in its definition of deepEqual, and QUnit has always implemented it that way. Hence neither the spec nor QUnit has any deepStrictEqual method. The choice of using loose == equality (arguably a mistake) appears to have been specific to Node.js.