chore(engine-server): run test fixtures concurrently

[cardoso]

Details

Small but easy improvement observed locally ~1.65s to ~1.25s.

This is still the longest-running test file (in subsequent runs), so this might help uncover other ways to improve.

Does this pull request introduce a breaking change?

• 😮‍💨 No, it does not introduce a breaking change.

Does this pull request introduce an observable change?

• 🤞 No, it does not introduce an observable change.

GUS work item

[wjhsf]

Pretty cool! Is there any perf gain if we do this for fixtures in other packages as well?

[cardoso]

@wjhsf yes, I have another PR coming up which refactors the test-fixture-dir.ts file and removes the custom toMatchFile sync matcher in favor of vitest's async toMatchFileSnapshot. I saw bigger improvements (~1s for this test), but wanted to push this simple one first to see the difference. It also improves the UX when using vitest through VSCode:

With the custom matcher it won't show the diff and file locations as nicely:

[nolanlawson]

/nucleus test

[nolanlawson]

Awesome!