Five fixtures forced a failure with chmod 500 on a parent directory. That
is silently useless for root: uid 0 bypasses the mode bits, the operation
succeeds, and a test asserting a failure path then reports the tool as
broken rather than the injection as ineffective.
CI runs the suite as root inside a container, so 21 checks failed there
while passing for every developer and every reviewer -- the same shape as
the git-identity gap in the previous commit. A fixture that quietly stops
injecting is worse than one that never existed: it reads as coverage.
Shim the single command each failure hinges on, matched by a path fragment
so nothing else in the run is disturbed. A command that exits 1 on purpose
does so for every uid. Which command matters: ensure_symlink removes an
existing link before it creates the new one, so the two adopt fixtures
have to fail at that rm to leave the live link in place, and shimming ln
would be too late. The restore fixture deletes the link first and so does
hinge on ln, and the failing --remote fixture hinges on git set-url.
The one remaining chmod 500 asserts a success, not a failure, and its real
proof is the direct assertions on where the stash landed.
Reproduce the root case locally without a container:
unshare -r fish tests/test-agents-vault.fish
Verified: 296/317 as root before, 317/317 after; 317/317 unchanged as an
ordinary user; and neutering the shims reproduces exactly 296/317, the
count CI reported.
The suite was hermetic against $HOME and ~/.claude but not against git
config. new_repo set an identity on the repos the tests create; nothing
set one on the repos the tool creates -- the scaffolded vault and the
AGENTS/ sub-repo. Those inherited a global user.name/user.email on a
developer machine and committed fine, so the gap was invisible to every
local run and every review; on a runner with no gitconfig they died with
"Author identity unknown", and the suite reported the tool own correct
"nothing recorded" handling as 71 failures.
Supply the identity through the environment, which reaches the git calls
inside agents-vault and agents-init as well as the ones the tests make.
Pin commit.gpgsign off for the mirror-image reason: a developer with
signing enabled would otherwise have tool-created repos reach for a key,
and a hardware token would prompt for a touch partway through the run.
Pin init.defaultBranch because the rebase fixtures build an upstream and a
clone and need the two to agree on a branch name. A global saying main and
a bare default of master disagree, and the fixture then fails to create the
rebase the test is about, reporting a tool failure that never happened.
Verified with GIT_CONFIG_GLOBAL=/dev/null GIT_CONFIG_SYSTEM=/dev/null:
267/317 before, 317/317 after; unchanged at 317/317 with a normal config.
rootiest