By changing the modified line below

Defaults env_reset, runas_default=rony

to

Defaults:test runas_default=rony

Now the user 'test' can run a command as user 'rony' and user 'rony' continues to use sudo like before. I think what happened was that since Defaults:......... was blank, it assumed runas 'rony' for all users. By specifying Defaults:test, the rule applied only to the user 'test'.

I have not tried it but does it mean that the line Defaults:..... can be set one below the other for different users and different respective rules?