Testing against outdated vendor libraries

[jgonggrijp]

The project is currently testing against local hardcopies of jQuery, json2, QUnit, require.js and Underscore. These versions are all outdated by at least seven years.

There is a real advantage to this: testing against old versions of dependencies safeguards backwards compatibility.

There is also an obvious disadvantage: the more outdated these dependencies become, the more likely it is that incompatibilities creep into newer versions, without the tests detecting them.

In my own projects, I use Backbone with the latest versions of Underscore and jQuery, and I haven't noticed any problems. So far, we might have gotten away with the outdatedness of the dependencies, thanks to the fact that jQuery and Underscore are both very stable. However, at some point, this streak of luck will likely end.

I am convinced that we need to test against recent versions of jQuery and Underscore. They can simply be sourced from the node_modules instead of test/vendor. I am less sure about the old versions; should we keep also testing against those or not?

Thoughts appreciated. CC @GammaGames

[GammaGames]

Wow, that version of jquery released almost 11 years ago! I've been using recent versions in our projects and haven't come across any issues, underscore at 1.13.2 and jquery at 3.6.3. I don't really see any value in testing against versions that old.