Test passed but the error message "Error: connect ECONNREFUSED 127.0.0.1:80" shows up

I'm writing test code with Jest and React Testing Library.

The code passes but it shows the error "Error: connect ECONNREFUSED 127.0.0.1:80".

This is the code.

describe('Purchase button', () => {
  test('It should be working and move to complete page', async () => {

:

    // Push 'Submit' button
    act(() => {
      fireEvent.click(getByText(/Submit/));
    })
    expect(spyAPI).toBeCalledWith(`${id}`);
    // Check moving to complete page.
    await waitFor(() => {
      expect(getByText(/Thank you, you have purchased/)).toBeInTheDocument();
    })
:

If the last line is commented out like the following, the error message is not there.

/*
await waitFor(() => {
  expect(getByText(/Thank you, you have purchased/)).toBeInTheDocument();
})
*/