feat(config): allow percentage value for workers option

[syi0808]

Description

I can't use maxWorkers option that jest supported after migrating to vitest.
So I modified it so that the percentage value can be used in maxworkers and minworkers.

jestjs/jest#9012 (comment)
Although it is a feature request in jest, I would like to get the same feature in viteest.

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[syi0808]

I want to add test for worker option but I found two problems.

1. Can't mock node:os inside bundled vitest/node
2. If i import resolveConfig function from package/vitest/node/config.ts to test, throw type error from runtime.

I don't think I can test the code properly if I can't mock node:os. Is it okay to test with cpus count without mocking?
Or is it okay to test only exception handling other than calculate logic?

[sheremet-va]

I want to add test for worker option but I found two problems.

1. Can't mock node:os inside bundled vitest/node
2. If i import resolveConfig function from package/vitest/node/config.ts to test, throw type error from runtime.

I don't think I can test the code properly if I can't mock node:os. Is it okay to test with cpus count without mocking? Or is it okay to test only exception handling other than calculate logic?

You can create a separate utility that accepts the workers number and the amount of CPU and test that function.

[syi0808]

I want to add test for worker option but I found two problems.

1. Can't mock node:os inside bundled vitest/node
2. If i import resolveConfig function from package/vitest/node/config.ts to test, throw type error from runtime.

I don't think I can test the code properly if I can't mock node:os. Is it okay to test with cpus count without mocking? Or is it okay to test only exception handling other than calculate logic?

You can create a separate utility that accepts the workers number and the amount of CPU and test that function.

Thanks for nice idea! I separate getWorkers function to utility and node:os mock is works. I added test now.

[sheremet-va]

vi.mock is always hoisted to the top of the file so it doesn't make a sense to have it inside describe function, let's put it at the top to make it less confusing. You can also use import syntac so you don't need to case the Record type:

Suggested change

	vi.mock('node:os', async importOriginal => ({
	vi.mock(import('node:os'), async importOriginal => ({

[syi0808]

Now that I look at it, I wonder how vi.mock worked. It's all reflected. thank you!

[syi0808]

test failed.. because maybe i changed node:os import method. I fix test in a minutes.