[API reference](https://evolu.dev/docs/api-reference) › [@evolu/common](https://evolu.dev/docs/api-reference/common) › [Assert](https://evolu.dev/docs/api-reference/common/Assert) › assertRejectsInstanceOf

```ts
function assertRejectsInstanceOf<T>(
  promise: PromiseLike<unknown>,
  constructor: T,
): Promise<InstanceType<T>>;
```

Defined in: [packages/common/src/Assert.ts:629](https://github.com/evoluhq/evolu/blob/ecbac001e0c18bbc45b44715f49ecc3a768c5ec9/packages/common/src/Assert.ts#L629)

Asserts that a promise rejects with an instance of a constructor.

Returns the narrowed instance so additional properties can be asserted.

### Example

```ts

const error = await assertRejectsInstanceOf(
  Promise.reject(new TypeError("Unavailable.")),
  TypeError,
);
assertEqual(error.message, "Unavailable.");
```