def is_valid_passphrase_part1(passphrase):
    """
    Tests that the given passphrase is valid by making sure it has no duplicate words.

    Parameters
    ----------
    passphrase : str
        The passphrase to be checked.

    Returns
    -------
    bool
        True if the passphrase has no duplicate words, otherwise False.
    """
    words = passphrase.split()
    unique_words = set(words)
    return len(words) == len(unique_words)