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54 lines
1.4 KiB
54 lines
1.4 KiB
2 years ago
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# Prefer `await expect(...).resolves` over `expect(await ...)` syntax (`prefer-expect-resolves`)
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When working with promises, there are two primary ways you can test the resolved
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value:
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1. use the `resolve` modifier on `expect`
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(`await expect(...).resolves.<matcher>` style)
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2. `await` the promise and assert against its result
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(`expect(await ...).<matcher>` style)
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While the second style is arguably less dependent on `jest`, if the promise
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rejects it will be treated as a general error, resulting in less predictable
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behaviour and output from `jest`.
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Additionally, favoring the first style ensures consistency with its `rejects`
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counterpart, as there is no way of "awaiting" a rejection.
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## Rule details
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This rule triggers a warning if an `await` is done within an `expect`, and
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recommends using `resolves` instead.
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Examples of **incorrect** code for this rule
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```js
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it('passes', async () => {
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expect(await someValue()).toBe(true);
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});
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it('is true', async () => {
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const myPromise = Promise.resolve(true);
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expect(await myPromise).toBe(true);
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});
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```
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Examples of **correct** code for this rule
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```js
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it('passes', async () => {
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await expect(someValue()).resolves.toBe(true);
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});
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it('is true', async () => {
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const myPromise = Promise.resolve(true);
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await expect(myPromise).resolves.toBe(true);
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});
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it('errors', async () => {
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await expect(Promise.rejects('oh noes!')).rejects.toThrow('oh noes!');
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});
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```
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