Each run step goes through mesh-sdk's buildstep.Isolated: no network, none of the account,
the workspace read-write, the Go caches beneath a throwaway layer unless the build step is
told publish (a trunk build). The integration level runs its store, its bus and its tests in
one shut-off process (this program again, level <spec>), so they reach each other and
nothing else. build_go_test takes a -run pattern (a try's tests). The module declares the
bubblewrap package and refuses a step, unhealthy, while bwrap is missing or older than 0.10.
The proof test runs a probe test through the real unit level.
jschoubben
eed6be0f4a