Port test suite to Jest

[ptomato]

This is something we've been talking about for a while. I started doing it for the upstream reference polyfill, but abandoned it because Jest was too memory-heavy to support the number of snapshot tests I wanted to do. However, that work was mostly reusable for this polyfill.

[ptomato]

Unfortunately I've run out of time for this without getting it to work ☹️

Jest's "resolver" option doesn't seem to work properly on Node 20.x and earlier. Here's the error:

> @js-temporal/polyfill@0.5.1 test /home/runner/work/temporal-polyfill/temporal-polyfill
> npm run build && node --no-warnings --experimental-modules --experimental-vm-modules --experimental-specifier-resolution=node --icu-data-dir node_modules/full-icu node_modules/.bin/jest


> @js-temporal/polyfill@0.5.1 build /home/runner/work/temporal-polyfill/temporal-polyfill
> rm -rf dist/* tsc-out/* && tsc && rollup -c rollup.config.js --bundleConfigAsCjs


tsc-out/index.js → ./dist/index.esm.js, ./dist/index.cjs...
created ./dist/index.esm.js, ./dist/index.cjs in 1s

tsc-out/index.js → ./dist/index.umd.js...
created ./dist/index.umd.js in 3.4s
● Validation Error:

  Module <rootDir>/jest.resolve.cjs in the resolver option was not found.
         <rootDir> is: /home/runner/work/temporal-polyfill/temporal-polyfill

  Configuration Documentation:
  https://jestjs.io/docs/configuration

npm ERR! Test failed.  See above for more details.
Error: Process completed with exit code 1.

The file that it claims not to find is right there, so I'm not sure what's going on. It also works on my machine, even with a copy of Node 18. Hopefully someone else can take this and run with it!

[fabon-f]

I can reproduce the issue when running npm ci --no-optional && npm test in Node.js v20.19.5 and npm v10.8.2. Without --no-optional option, it works fine.

npm ci --no-optional seems to skip all "optional" packages including platform-specific binary package needed by Jest (in this case @unrs/resolver-binding-linux-x64-gnu for Linux) in older npm.

[ptomato]

Thanks, that fixed Node 18.x and 20.x, but there is still the same error on 16.x, and a different error on 14.x.

[fabon-f]

Jest v30 supports only Node.js v18 and later, so I think there are two options: use older Jest v29 which supports Node.js v14 and v16, or stop testing for EOL versions (v14, v16).

[ptomato]

That did it, thank you @fabon-f!

This is ready for merging now, I think.

[justingrant]

Amazing! Nice work making this happen.

[ptomato]

Thanks for the review.