🛠️ Repo: Change assertion syntax from string to chain

[mark-wiemer]

Tooling Suggestion Checklist

• I have tried restarting my IDE and the issue persists.
• I have pulled the latest main branch of the repository.
• I have read and agree to Mocha's Code of Conduct and Contributing Guidelines
• I have searched for related issues and issues with the faq label, but none matched my issue.
• I want to provide a PR to resolve this

Overview

Mocha's internal tests are currently using a customized fork of unexpected with assertions like expect(x, 'not to equal', y), but popular assertion libraries often use expect(x).not.toEqual(y) for easier chaining and IntelliSense suggestions. We should update our internal assertion syntax to be more consistent with these popular libraries for improved developer experience.

Additional Info

This probably won't improve consistency of our tests, but it'll be easier for others to contribute!

[mark-wiemer]

Unexpected is still relatively well-maintained, I think I had it confused for a different library. That said, our use of assertions like "not to equal" instead of .not.toEqual really throws me off and is something I'd still like to change. Renaming the issue accordingly

Edit: Ugh, I am always premature with this stuff. Unexpected was last updated in July 2023, I'm happy to move to Chai for this work. Going to keep the new issue title as the main focus is the assertion syntax and not the tool underlying the assertions.

[JoshuaKGoldberg]

My vote is to move to Chai. It's a great common standard(-ish) and has an API that we generally have aimed for in the past.