def test_get_config_filename_not_set():
    """
    If the envvar is not set, not filename is returned.

    """
    metadata = Metadata("foo-bar")
    config_filename = get_config_filename(metadata)
    assert_that(config_filename, is_(none()))
def test_get_config_filename():
    """
    If the envvar is set, it is used as the filename.

    """
    metadata = Metadata("foo-bar")
    with envvar("FOO_BAR_SETTINGS", "/tmp/foo-bar.conf"):
        config_filename = get_config_filename(metadata)
        assert_that(config_filename, is_(equal_to("/tmp/foo-bar.conf")))