38 lines
781 B
Markdown
38 lines
781 B
Markdown
# Suggest using `toBeUndefined()` (`prefer-to-be-undefined`)
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## Deprecated
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This rule has been deprecated in favor of [`prefer-to-be`](prefer-to-be.md).
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In order to have a better failure message, `toBeUndefined()` should be used upon
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asserting expectations on undefined value.
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## Rule details
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This rule triggers a warning if `toBe()`, `toEqual()` or `toStrictEqual()` is
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used to assert an undefined value.
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```js
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expect(undefined).toBe(undefined);
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```
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This rule is enabled by default.
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### Default configuration
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The following patterns are considered warnings:
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```js
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expect(undefined).toBe(undefined);
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expect(undefined).toEqual(undefined);
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expect(undefined).toStrictEqual(undefined);
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```
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The following pattern is not warning:
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```js
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expect(undefined).toBeUndefined();
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```
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