1.4 KiB
1.4 KiB
Prefer await expect(...).resolves
over expect(await ...)
syntax (prefer-expect-resolves
)
When working with promises, there are two primary ways you can test the resolved value:
- use the
resolve
modifier onexpect
(await expect(...).resolves.<matcher>
style) await
the 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.
Rule details
This rule triggers a warning if an await
is done within an expect
, and
recommends using resolves
instead.
Examples of incorrect code for this rule
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
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.rejects('oh noes!')).rejects.toThrow('oh noes!');
});