You need to add some repositories.
From looking at the OpenSUSE listing for stress, I think you can get it from the server:monitoring repository.
With SUSE 11, I _think_ this command should add the repository.
cd /tmp
wget "
zypper addrepo "server:monitoring.repo"
With CentOS 7, maybe the CentOS 6 repository from the same site will work? Try:
yum-config-manager --add-repo "
Then try the `zypper install` or `yum install` again, e.g.
zypper refresh
zypper install stress
or
yum install stress