def test_apt_preferences_docker_compose_file(host):
    f = host.file("/etc/apt/preferences.d/docker-compose")
    assert f.exists
    assert f.is_file


def test_apt_preferences_docker_file(host):
    f = host.file("/etc/apt/preferences.d/docker")
    assert f.exists
    assert f.is_file

def test_apt_preferences_docker_compose_file(host):
    f = host.file("/etc/apt/preferences.d/docker-compose")
    assert f.exists
    assert f.is_file


def test_apt_preferences_docker_file(host):
    f = host.file("/etc/apt/preferences.d/docker")
    assert f.exists
    assert f.is_file


def test_systemd_overlay_file(host):
    f = host.file("/etc/systemd/system/docker.service.d/overlay.conf")
    assert f.exists
    assert f.is_file


def test_limits_file(host):
    f = host.file("/etc/security/limits.d/docker.conf")
    assert f.exists
    assert f.is_file

Add further testinfra tests