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node_modules/eslint-plugin-jest/docs/rules/prefer-to-be-undefined.md

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