def METHOD_NAME(rule_runner: PythonRuleRunner) -> None:
    rule_runner.write_files(
        {"good.py": GOOD_FILE, "bad.py": BAD_FILE, "BUILD": "python_sources(name='t')"}
    )
    tgts = [
        rule_runner.get_target(Address("", target_name="t", relative_file_path="good.py")),
        rule_runner.get_target(Address("", target_name="t", relative_file_path="bad.py")),
    ]
    fmt_result = run_add_trailing_comma(rule_runner, tgts)
    assert fmt_result.output == rule_runner.make_snapshot(
        {"good.py": GOOD_FILE, "bad.py": GOOD_FILE}
    )
    assert fmt_result.did_change is True