Looking at the script you wanted to run, it looks like this is in a unix/linux environment. You can modify test.sh as a launcher instead of the actual process. test.sh can be used to spawn off a "detached" background process (not just a background process, but a detached process).

A simple way is to use the unix 'at' command:

test.sh
-------------
#!/bin/sh
at now << EOF > /dev/null 2>&1
#!/bin/sh
# Put your commands here
ls > /tmp/output.txt
EOF
-------------

Note that if your commands generate output and if the output is not redirected to a file, the 'at' command will send you an email with the output. That can get annoying.