def tuple_for_testing(model, val, replace_i):
    """this function creates a tuple by changing only one parameter from a list
    
    Positionnal arguments :
        model -- a list of valid arguments to pass to the object to test
        val -- the value you want to put in the list
        replace_i -- the index of the value to be replaced
    
    Returns :
        tuple
    """
    m_copy = model.copy()
    m_copy[replace_i]=val
    return tuple(m_copy)