def mktestFfile(tmpdir_factory):
    """Creates test file for unit testing in tempFdir.

    :param tmpdir_factory:
    :returns: path of file for pin 435 test
    """
    tempFdir = tmpdir_factory.mktemp('tempF')
    testFile = tempFdir.join('L435L0.BIN')
    test435Path = testFile.strpath
    with open('./testing/435L0.BIN', 'rb') as binaryFile:
        hold = binaryFile.read()
    with open(test435Path, 'wb') as binaryFile:
        binaryFile.write(hold)
    return test435Path