import pytest
from mifarepy import Handle, GNetPlusError

def test_handle_initialization():
    """Test that Handle raises an error with an invalid port."""
    with pytest.raises(RuntimeError):
        Handle('/dev/fakeport')

def test_get_sn_format():
    """Test that get_sn returns a string when as_string=True."""
    handle = Handle('/dev/ttyUSB0')  # Assuming mock or test environment
    assert isinstance(handle.get_sn(as_string=True), str)

def test_get_sn_integer():
    """Test that get_sn returns an integer when as_string=False."""
    handle = Handle('/dev/ttyUSB0')  # Assuming mock or test environment
    assert isinstance(handle.get_sn(as_string=False), int)

def test_auto_mode():
    """Ensure auto mode can be toggled without errors."""
    handle = Handle('/dev/ttyUSB0')  # Assuming mock or test environment
    response = handle.set_auto_mode(enabled=True)
    assert response in [b'\x00', b'\x01']  # Expecting response from device
