it.each/describe.each break when single-dimensional array contains 0 (numeric zero)

[mgdodge]

Describe the bug

Migrating tests from jest to Vitest, the way describe.each and it.each function is buggy. According to the jest docs, using describe.each or it.each should internally convert a single-dimensional array to a multidimensional array. For example, [1, 2, 0] would be converted to [[1], [2], [0]]. This is a very common scenario for simple tests.

Unfortunately, using the single-dimensional array syntax with Vitest v0.4.1, testing with [1, 2, 0] fails when running the test for 0 (numeric zero). It seems that the value gets converted to undefined!

I did find the comment in #640 indicating that template literal usage is intentionally left out, but it makes no mention of single-dimensional arrays, which I see as being far more common. If single-dimensional arrays are also being omitted, then I think the docs need to be updated to call out these differences.

Reproduction

[1, 2, 0].forEach((num) => {
	it(`${num} is a number (foreach)`, () => {
		expect(typeof num).toEqual('number');
	});
});

it.each([1, 2, 0])('%s is a number (it.each 1d)', (num) => {
	expect(typeof num).toEqual('number');
});

it.each([
	[1],
	[2],
	[0],
])('%s is a number (it.each 2d)', (num) => {
	expect(typeof num).toEqual('number');
});

describe.each([1, 2, 0])('%s (describe.each 1d)', (num) => {
	it(`${num} is a number (describe.each 1d)`, () => {
		expect(typeof num).toEqual('number');
	});
});

describe.each([
	[1],
	[2],
	[0],
])('%s (describe.each 2d)', (num) => {
	it(`${num} is a number (describe.each 2d)`, () => {
		expect(typeof num).toEqual('number');
	});
});

     √ 1 is a number (foreach)
     √ 2 is a number (foreach)
     √ 0 is a number (foreach)
     √ 1 is a number (it.each 1d)
     √ 2 is a number (it.each 1d)
     × %s is a number (it.each 1d)
     √ 1 is a number (it.each 2d)
     √ 2 is a number (it.each 2d)
     √ 0 is a number (it.each 2d)
     √ 1 (describe.each 1d) (1)
     √ 2 (describe.each 1d) (1)
     ❯ %s (describe.each 1d) (1)
       × undefined is a number (describe.each 1d)
     √ 1 (describe.each 2d) (1)
     √ 2 (describe.each 2d) (1)
     √ 0 (describe.each 2d) (1)

Failing tests result in AssertionError: expected 'undefined' to deeply equal 'number'

System Info

  System:
    OS: Linux 5.10 Ubuntu 20.04.3 LTS (Focal Fossa)
    CPU: (8) x64 11th Gen Intel(R) Core(TM) i9-11950H @ 2.60GHz
    Memory: 25.69 GB / 31.36 GB
    Container: Yes
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 16.13.1 - ~/.nvm/versions/node/v16.13.1/bin/node
    npm: 8.1.2 - ~/.nvm/versions/node/v16.13.1/bin/npm
  npmPackages:
    @vitejs/plugin-vue: ^2.2.2 => 2.2.2
    vite: ^2.8.4 => 2.8.4
    vitest: ^0.4.1 => 0.4.1

Used Package Manager

npm

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