For openSUSE 42.3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/OBS:Server:2.8:Staging/openSUSE_42.3/OBS:Server:2.8:Staging.repo
zypper refresh
zypper install rubygem-mocha
For openSUSE 42.2 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/OBS:Server:2.8:Staging/openSUSE_42.2/OBS:Server:2.8:Staging.repo
zypper refresh
zypper install rubygem-mocha
For openSUSE 42.1 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/OBS:Server:2.8:Staging/openSUSE_42.1/OBS:Server:2.8:Staging.repo
zypper refresh
zypper install rubygem-mocha