Function rejectionOf

rejectionOf<TErrorType = any>(promise: Promise<any>): Promise<TErrorType>
Test function. Checks that an async function throws an error on execution. It returns the thrown error. Allows easier inspection of the thrown error.
Type Parameters
- TErrorType = any
Parameters
- promise: Promise<any>
Returns Promise<TErrorType>
Example
```
 const error = await rejectionOf<MosaicError>(handler.onMessage(body, message));

 expect(error.message).toBe('Some error message');
 expect(error.code).toBe('SOME_CODE');
```
For synchronous functions use expectFailure