Sinon.JS is ubiquitous in Wikimedia's repositories. However, the version used is outdated and now six major versions behind. The consequence is that developers cannot apply best practice and instead proliferates technical debt. Projects such as MobileFrontend have already begun to deviate. This task encompasses the work to revise the version provided in Core, identify common upgrade failure patterns in Core, skins, and extensions, and open tasks or patches for their resolution.
- The latest version of Sinon.JS is usable everywhere.
- Previously passing tests still pass.