def METHOD_NAME(testdata_dir: pathlib.Path) -> None:
    """Test jinja datestamp generation, with format string."""
    jinja_md_dir = testdata_dir / JINJA_MD
    jinja_env = Environment(loader=FileSystemLoader(jinja_md_dir), extensions=[tres_jinja.MDDatestamp])
    with pytest.raises(Exception):
        _ = jinja_env.get_template('MDDatestamp_invalid.jinja.md')