---
url: /docs/guide/usage/linter/rules/jest/prefer-jest-mocked.md
---

### What it does

When working with mocks of functions using Jest, it's recommended to use the
`jest.mocked()` helper function to properly type the mocked functions. This rule
enforces the use of `jest.mocked()` for better type safety and readability.

Restricted types:

* `jest.Mock`
* `jest.MockedFunction`
* `jest.MockedClass`
* `jest.MockedObject`

### Why is this bad?

Using type assertions like `fn as jest.Mock` is a less safe approach
than using `jest.mocked()`. The `jest.mocked()` helper provides better
type safety by preserving the original function signature while adding
mock capabilities. It also makes the code more readable and explicit
about mocking intentions.

### Examples

Examples of **incorrect** code for this rule:

```typescript
(foo as jest.Mock).mockReturnValue(1);
const mock = (foo as jest.Mock).mockReturnValue(1);
(foo as unknown as jest.Mock).mockReturnValue(1);
(Obj.foo as jest.Mock).mockReturnValue(1);
([].foo as jest.Mock).mockReturnValue(1);
```

Examples of **correct** code for this rule:

```typescript
jest.mocked(foo).mockReturnValue(1);
const mock = jest.mocked(foo).mockReturnValue(1);
jest.mocked(Obj.foo).mockReturnValue(1);
jest.mocked([].foo).mockReturnValue(1);
```

## How to use

## Version

This rule was added in v0.5.0.

## References