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53 lines
1.4 KiB
53 lines
1.4 KiB
# 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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