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54 lines
1.6 KiB
54 lines
1.6 KiB
2 years ago
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# Suggest using `toBe()` for primitive literals (`prefer-to-be`)
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When asserting against primitive literals such as numbers and strings, the
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equality matchers all operate the same, but read slightly differently in code.
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This rule recommends using the `toBe` matcher in these situations, as it forms
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the most grammatically natural sentence. For `null`, `undefined`, and `NaN` this
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rule recommends using their specific `toBe` matchers, as they give better error
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messages as well.
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## Rule details
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This rule triggers a warning if `toEqual()` or `toStrictEqual()` are used to
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assert a primitive literal value such as numbers, strings, and booleans.
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The following patterns are considered warnings:
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```js
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expect(value).not.toEqual(5);
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expect(getMessage()).toStrictEqual('hello world');
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expect(loadMessage()).resolves.toEqual('hello world');
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```
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The following pattern is not warning:
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```js
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expect(value).not.toBe(5);
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expect(getMessage()).toBe('hello world');
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expect(loadMessage()).resolves.toBe('hello world');
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expect(didError).not.toBe(true);
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expect(catchError()).toStrictEqual({ message: 'oh noes!' });
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```
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For `null`, `undefined`, and `NaN`, this rule triggers a warning if `toBe` is
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used to assert against those literal values instead of their more specific
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`toBe` counterparts:
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```js
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expect(value).not.toBe(undefined);
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expect(getMessage()).toBe(null);
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expect(countMessages()).resolves.not.toBe(NaN);
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```
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The following pattern is not warning:
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```js
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expect(value).toBeDefined();
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expect(getMessage()).toBeNull();
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expect(countMessages()).resolves.not.toBeNaN();
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expect(catchError()).toStrictEqual({ message: undefined });
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```
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