import os.path

def test_open_cachefile_creates(monkeypatch, tmp_path):
    monkeypatch.setenv('MOULINETTE_CACHE_DIR', str(tmp_path))

    from moulinette.cache import open_cachefile

    handle = open_cachefile('foo.cache', mode='w')

    assert handle.mode == 'w'
    assert handle.name == os.path.join(str(tmp_path), 'foo.cache')