Stable Branch Testing Policy
Tempest and its plugins need to support the stable branches as per Stable Branch Support Policy </stable_branch_support_policy>.
Because of branchless model of Tempest and plugins, all the supported stable branches use the Tempest and plugins master version for their testing. That is done in devstack by using the master branch for the Tempest installation. To make sure the master version of Tempest or plugins (for any changes or adding new tests) is compatible for all the supported stable branches testing, Tempest and its plugins need to add the stable branches job on the master gate. That way can test the stable branches against master code and can avoid breaking supported branches accidentally.
Once any stable branch is moved to the Extended Maintenance Phases and devstack start using the Tempest older version for that stable branch testing then we can remove that stable branch job from master gate.