Talk given at HPSF 2026 as part of the Spack Project Meeting.
We've significantly optimized our development workflow by experimentally integrating Spack in our nightly testsuite. In the process, we encountered unique challenges adapting a package manager primarily intended for end-users on our existing CI runners and developed custom tools to port our existing jobs to utilize Spack. The outcome is that our testsuite builds are now aggressively cached and minimize internal dependency rebuilds. Additionally, our job environments can now be declaratively reproduced without recompilation by any member of our team. We hope that our results inspire others to consider attempting a similar endeavor and reap the benefits of functional package management within their own projects.