chore: migrate from Jest to Vitest

[wojtekmaj]

Requires #2409.

Requires #2494.

Migrates the entire monorepo from Jest to Vitest.

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[diegomura]

@wojtekmaj Just to understand this better (not familiarized with vitest), the benefit of this is better support for ESM and more performant? About the latter I'm not so concern as the entire testsuite runs in like 6sec. Also curious how tight this lib is to vite, considering we don't use it here

[diegomura]

Actually, about performance, I tested this branch and tests take 50% more to run (9s). It's not bad either s not concerned, but still curious :)

[wojtekmaj]

There are multiple reasons to go with Vitest. It's quickly raising popularity for good reasons.

Better ESM support and better (and ever-improving) performance are some of them. The importance of the former is only going to get bigger, as more and more modules go ESM-only.

Other benefits:

• Fewer dependencies, faster installs
• Easier, less error prone configuration
• No globals clashes when working with another test runner (e.g. Playwright)

[wojtekmaj]

Hmmm, interesting. You're right that the overall run time has increased a bit, and this is while the individual tests run faster:

Before:
PASS packages/renderer/tests/resume.test.js (6.884 s)

After:
✓ |renderer| tests/resume.test.jsx (3 tests) 3767ms

Before:
PASS packages/renderer/tests/pageWrap.test.js (7.924 s)

After:
✓ |renderer| tests/pageWrap.test.jsx (1 test) 3553ms

This makes me convinced that while there is probably something I could still tweak, the more tests and the more complex they are, the faster Vitest will be in relation to Jest.

[wojtekmaj]

Now it's 35% faster than Jest on CI! ;)