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docs(migration): prefer for naming and use realistic inference break example
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docs/guide/migration.md
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docs/guide/migration.md
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test('example', { concurrent: false }, async () => { /* ... */ }) // [!code ++]
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```
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### Narrower Inference for `test.each` and `describe.each`
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### Narrower Inference for `test.for` and `describe.for`
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`test.each` and `describe.each` now preserve literal types by default for array cases.
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`test.for` and `describe.for` now preserve literal types by default for array cases.
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This means callback parameters can be inferred as literal unions (for example `1 | 2`) instead of widened types (for example `number`) without needing `as const`.
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If your callback annotations intentionally reject literal values and relied on wider inference, update those annotations to accept the inferred literal unions.
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`test.each` and `describe.each` are compatibility aliases and follow the same typing behavior.
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If your tests rely on wide callback inference, either widen the value before passing it to broader helpers or specify the case type explicitly.
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```ts
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// Vitest 5 infers `value` as `1 | 2`, so this callback is now too narrow:
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test.each([1, 2])('value %s', (value: Exclude<number, 1 | 2>) => {}) // [!code --]
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function runWithRuntimeRetry(fn: (retry: number) => void) {
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fn(Math.trunc(Math.random() * 10))
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}
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// If you need the previous wide inference, specify the case type explicitly:
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test.each<number>([1, 2])('value %s', (value: Exclude<number, 1 | 2>) => {}) // [!code ++]
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test.for([1, 2])('retry %s', (retry) => { // [!code --]
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runWithRuntimeRetry((runtimeRetry) => {
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const sameType: typeof retry = runtimeRetry
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// ^ Type 'number' is not assignable to type '1 | 2'
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})
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})
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test.for<number>([1, 2])('retry %s', (retry) => { // [!code ++]
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runWithRuntimeRetry((runtimeRetry) => {
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const sameType: typeof retry = runtimeRetry
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})
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})
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```
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### Locators in Commands are Serialized as Objects