how to login other user account with shell script

hi to all
i want the shell script that automatically login to other user account


suppose i login as a username:yoga
password:abcdef

at prompt i make one test.sh script

test.sh  //data in this file
su root                 //want to login as a root user name
xyzabc              //password


so when i run this shell script the o/p like this

yoga# ./test.sh
password:


but i want to directly login .i want to password in shell script

so the o/p will come like below

yoga# ./test.sh
root#

can it possible if yes than how

thanks in advance