When rendering full pages in unit tests, we were triggering Pipeline's

media compilation. This wasn't a problem before, because we had overridden

the list of Pipeline compilers, but we now hard-code Rollup if we opt in.

Rollup ends up triggering some long compilations in this environment, and

potentially was triggering some bad behavior somewhere, as it was resulting

in some stalled tests that had to be force-killed.
We now skip Pipeline entirely when running unit tests.

All unit tests pass.