For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/isv:SUSEInfra:ITPE:Tools/openSUSE_Tumbleweed/isv:SUSEInfra:ITPE:Tools.repo
zypper refresh
zypper install gotestsum
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/isv:SUSEInfra:ITPE:Tools/15.6/isv:SUSEInfra:ITPE:Tools.repo
zypper refresh
zypper install gotestsum
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/isv:SUSEInfra:ITPE:Tools/15.5/isv:SUSEInfra:ITPE:Tools.repo
zypper refresh
zypper install gotestsum