Linked Moment Tests don't support bugs argument?

[micnguyen]

In the README, there's a line that says It is mutable due to OOP APIs and non-pure functions, which cause bugs: with a link to https://github.com/moment/moment/blob/develop/src/test/moment/add_subtract.js#L244-L286

I'm looking at these tests and I can't seem to pin point why these tests might support the line which cause bugs. Sure, the API is a bit verbose and it is OOP vs pure, but I don't think it's buggy.

[stevemao]

I did a git blame and saw @ddvkid wrote that line.

[andrew-yangy]

Good catch, I will make an update on that, thanks!