You can take the backup of

Master key as well as the Certificate with the below mentioned scripts:

From the Instance which you've restored from your backup

backup master key to file = 'c:\mk.dat'

encryption by password = 'Pass@12'

backup certificate mycert to file = 'c:\cert21.dat'

with private key(

encryption by password = 'sarab',

file = 'c:\cert21_key.dat')

To Restore the same on your test server Use these Scripts

restore master key from file = 'Z:\mk.dat'

decryption by password = 'Pass@12'

encryption by password = 'Pass@12'

create certificate mycert from file = 'Z:\cert21.dat'

with private key(file = 'Z:\cert21_key.dat',

decryption by password = 'sarab')

NOTE: Use Encryption by option while creating\Restoring Certificate\Master Key only if you specified the password while creating Master Key or Certificate on your server & use the same password in the ENCRYPTION BY option.

Test this if u face any problem, let me know.