[chef] How to set an attribute inside a cookbook?

[Anthony Kong < >]

Hi,

I want to set an attribute in another cookbook otherwise it will fail during 'kitchen converge'

       Chef::Exceptions::ValidationFailed

       ----------------------------------

       Required argument password is missing!

        23:

        24:  # Set password according to attribute, if set

        25:  mysqld_password 'root' do

        26>>   password node['mysqld']['root_password']

I have tried these 

node['mysqld']['root_password'] = 'password'

and 

node.default['mysqld']['root_password'] = 'password'

before this line

include_recipe "mysqld"

But apparently it has no effect.

What is the proper way to set a variable of a included cookbook?