nunit3 from home:Simmphonie:mono project
Select Your Operating System
Add repository and install manually
For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Simmphonie:mono/openSUSE_Tumbleweed/home:Simmphonie:mono.repo zypper refresh zypper install nunit3