Currently tests are running outside of Bazel's sandbox. Enabling sandboxing would allow us to enable test caching and to generally improve consistency of test results of unit tests. There are currently a few tests that are non-hermetic that need to be made hermetic (unaffected by anything outside of the sandbox) before we can enable sandboxing.

By enabling test caching we would likely save hundreds of thousands of dollars a year in compute spend and also dramatically speed up cycle times waiting for CI results.