def is_triple_double(word):
    """Tests if a word contains three consecutive double letters.
    
    word: string

    returns: bool
    """
    i = 0
    count = 0
    while i < len(word)-1:
        if word[i] == word[i+1]:
            count = count + 1
            if count == 3:
                return True
            i = i + 2
        else:
            count = 0
            i = i + 1
    return False