56 lines
1.7 KiB
Markdown
56 lines
1.7 KiB
Markdown
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# Suggest using the built-in comparison matchers (`prefer-comparison-matcher`)
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Jest has a number of built-in matchers for comparing numbers which allow for
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more readable tests and error messages if an expectation fails.
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## Rule details
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This rule checks for comparisons in tests that could be replaced with one of the
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following built-in comparison matchers:
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- `toBeGreaterThan`
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- `toBeGreaterThanOrEqual`
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- `toBeLessThan`
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- `toBeLessThanOrEqual`
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Examples of **incorrect** code for this rule:
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```js
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expect(x > 5).toBe(true);
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expect(x < 7).not.toEqual(true);
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expect(x <= y).toStrictEqual(true);
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```
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Examples of **correct** code for this rule:
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```js
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expect(x).toBeGreaterThan(5);
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expect(x).not.toBeLessThanOrEqual(7);
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expect(x).toBeLessThanOrEqual(y);
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// special case - see below
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expect(x < 'Carl').toBe(true);
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```
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Note that these matchers only work with numbers and bigints, and that the rule
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assumes that any variables on either side of the comparison operator are of one
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of those types - this means if you're using the comparison operator with
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strings, the fix applied by this rule will result in an error.
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```js
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expect(myName).toBeGreaterThanOrEqual(theirName); // Matcher error: received value must be a number or bigint
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```
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The reason for this is that comparing strings with these operators is expected
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to be very rare and would mean not being able to have an automatic fixer for
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this rule.
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If for some reason you are using these operators to compare strings, you can
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disable this rule using an inline
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[configuration comment](https://eslint.org/docs/user-guide/configuring/rules#disabling-rules):
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```js
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// eslint-disable-next-line jest/prefer-comparison-matcher
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expect(myName > theirName).toBe(true);
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```
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