def METHOD_NAME(self):
    """Sanity checks the strip_prefix feature.
    """
    # Create some sample data.
    url = "http://127.0.0.1/example.zip"
    data, sha256 = self._create_sample_zip()
    self._url_contents[url] = data
    # Call the module under test.
    self._call_main(package_name="some_name", urls=[url], sha256=sha256,
                    strip_prefix="hello")
    # Check that the downloader stripped off "hello".
    output_dir = self._output_parent_dir / sha256
    with open(f"{output_dir}/world", encoding="utf-8") as f:
        hello = f.read()
    self.assertEqual(hello, "Hello, world!")