jest/prefer-expect-resolves Style
What it does
Prefer await expect(...).resolves over expect(await ...) when testing promises.
Why is this bad?
When working with promises, there are two primary ways you can test the resolved value:
- use the
resolvemodifier onexpect(await expect(...).resolves.<matcher>style) awaitthe promise and assert against its result (expect(await ...).<matcher>style)
While the second style is arguably less dependent on jest, if the promise rejects it will be treated as a general error, resulting in less predictable behaviour and output from jest.
Additionally, favoring the first style ensures consistency with its rejects counterpart, as there is no way of "awaiting" a rejection.
Examples
Examples of incorrect code for this rule:
javascript
it("passes", async () => {
expect(await someValue()).toBe(true);
});
it("is true", async () => {
const myPromise = Promise.resolve(true);
expect(await myPromise).toBe(true);
});Examples of correct code for this rule:
javascript
it("passes", async () => {
await expect(someValue()).resolves.toBe(true);
});
it("is true", async () => {
const myPromise = Promise.resolve(true);
await expect(myPromise).resolves.toBe(true);
});
it("errors", async () => {
await expect(Promise.reject(new Error("oh noes!"))).rejects.toThrowError("oh noes!");
});How to use
To enable this rule using the config file or in the CLI, you can use:
json
{
"plugins": ["jest"],
"rules": {
"jest/prefer-expect-resolves": "error"
}
}ts
import { defineConfig } from "oxlint";
export default defineConfig({
plugins: ["jest"],
rules: {
"jest/prefer-expect-resolves": "error",
},
});bash
oxlint --deny jest/prefer-expect-resolves --jest-pluginVersion
This rule was added in v0.2.14.