# bun:test/prefer-mock-promise-shorthand

> Require `mockResolvedValue()` and `mockRejectedValue()` for mocks that return a promise

`mockReturnValue(Promise.resolve(user))` and `mockImplementation(() => Promise.resolve(user))` do the same thing as `mockResolvedValue(user)` with more code. The same goes for `Promise.reject()` and `mockRejectedValue()`, and for the `Once` version of each method.

`--fix` rewrites the call.

## Configure

Off by default. To turn it on:

```toml bunfig.toml
[lint.rules]
"bun:test/prefer-mock-promise-shorthand" = "error" # or "warn"
```

## Examples

Reported:

```ts
import { mock } from "bun:test";

const fetchUser = mock().mockReturnValue(Promise.resolve({ name: "Ada" }));
const saveUser = mock().mockImplementationOnce(() => Promise.reject(new Error("offline")));
```

Not reported:

```ts
import { mock } from "bun:test";

const fetchUser = mock().mockResolvedValue({ name: "Ada" });
const saveUser = mock().mockRejectedValueOnce(new Error("offline"));
```

An implementation that takes parameters is allowed, because its result can depend on them:

```ts
import { mock } from "bun:test";

const fetchUser = mock().mockImplementation((id: number) => Promise.resolve({ id }));
```