window.alert = jest.fn();
expect(window.alert).toHaveBeenCalledTimes(1);

async handleSubmit(event: React.FormEvent<HTMLFormElement>) {
   // check for errors
    if (errors) {
        window.alert('Some Error occurred');
        return;
    }
}

it('alerts on submit click', async () => {
  const alertMock = jest.spyOn(window,'alert');
  const { getByText, getByTestId } = render(<Form />)
  fireEvent.click(getByText('Submit'))
  expect(alertMock).toHaveBeenCalledTimes(1)
})