improvise/scripts/checkers-test.sh

#!/usr/bin/env bash
# check_the_checker for scripts/checkers.sh. Every case injects a fault that
# a bare `./scripts/X-test.sh` cannot see, and asserts the runner does.
# See context/test-evidence/tooling.md.
set -uo pipefail

here="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
RUNNER="$here/checkers.sh"
work="$(mktemp -d)"
trap 'rm -rf "$work"' EXIT

pass=0; fail=0
ok()  { printf '  ok   %s\n' "$1"; pass=$((pass+1)); }
bad() { printf '  FAIL %s (%s)\n' "$1" "$2"; fail=$((fail+1)); }

# A sandbox is a copy of the runner beside fixture suites, so `$HERE` inside it
# is the sandbox: the shebang scan and the suite list are both the fixtures'.
sandbox() {
  local d="$work/$1"
  mkdir -p "$d"
  cp "$RUNNER" "$d/checkers.sh"
  chmod +x "$d/checkers.sh"
  printf '%s' "$d"
}

# A suite is only discovered when the thing it checks is present, so every
# fixture gets a stub subject beside it.
suite() {
  local d="$1" name="$2"
  cat > "$d/$name-test.sh"
  chmod +x "$d/$name-test.sh"
  printf '#!/usr/bin/env bash\nexit 0\n' > "$d/$name.sh"
  chmod +x "$d/$name.sh"
}

# $1 name, $2 expected exit, rest: the command. Nothing follows the runner in
# its own pipeline, which is the rule its own header states.
expect() {
  local what="$1" want="$2"; shift 2
  "$@" > "$work/out" 2>&1
  local got=$?
  [ "$got" = "$want" ] && ok "$what" || bad "$what" "exit $got, wanted $want"
}

# ---------------------------------------------------------------------------
# 1. The fault this runner exists for. `nix develop` exports `name`; a suite
# that reads an unset variable under `set -u` is therefore SILENT in the dev
# shell and fatal in CI. That is improvise-f9qf, reproduced exactly.
d="$(sandbox setu)"
suite "$d" masked <<'EOF'
#!/usr/bin/env bash
set -euo pipefail
echo "read: $name"
EOF
export name=nix-shell-env
expect "a suite reading an inherited dev-shell variable fails under the runner" \
  1 "$d/checkers.sh" masked

# The same suite run the way the old gate ran it PASSES, which is what makes
# the case above discriminating rather than a test of `set -u`.
"$d/masked-test.sh" > "$work/out" 2>&1
direct=$?
[ "$direct" = 0 ] \
  && ok "and passes when run directly with that variable exported" \
  || bad "and passes when run directly with that variable exported" \
         "exit $direct, wanted 0"
unset name

# ---------------------------------------------------------------------------
# 2. The bash-5 `local` semantics. A multi-assignment `local` does not read
# left to right on bash 5, so this suite passes on macOS bash 3.2 and dies
# under `set -u` on bash 5 -- PR #133's 19/19 local against 2/19 in CI.
d="$(sandbox bash5)"
suite "$d" vers <<'EOF'
#!/usr/bin/env bash
set -euo pipefail
f() { local a="$1" b="$a/x"; echo "$b"; }
f one
EOF
expect "a bash-3.2-only construct fails under the runner's pinned bash" \
  1 "$d/checkers.sh" vers

# ---------------------------------------------------------------------------
# 3. The shebang rule. `#!/bin/sh` is dash in CI and bash-in-sh-mode on macOS.
d="$(sandbox shebang)"
suite "$d" fine <<'EOF'
#!/usr/bin/env bash
exit 0
EOF
printf '#!/bin/sh\nexit 0\n' > "$d/legacy.sh"
chmod +x "$d/legacy.sh"
expect "a #!/bin/sh script in the scripts directory is refused" 1 \
  "$d/checkers.sh" fine
grep -q 'wanted #!/usr/bin/env bash' "$work/out" \
  && ok "and the refusal names the shebang it wanted" \
  || bad "and the refusal names the shebang it wanted" "no such message"

# Without the injected file the same sandbox passes, so the case above is not
# passing on some other complaint.
rm -f "$d/legacy.sh"
expect "and the same sandbox passes once it is removed" 0 "$d/checkers.sh" fine

# ---------------------------------------------------------------------------
# 4. A failing suite is reported, and a passing one is not.
d="$(sandbox rc)"
suite "$d" red <<'EOF'
#!/usr/bin/env bash
exit 1
EOF
expect "a failing suite fails the runner" 1 "$d/checkers.sh" red

d="$(sandbox green)"
suite "$d" blue <<'EOF'
#!/usr/bin/env bash
exit 0
EOF
expect "a passing suite passes the runner" 0 "$d/checkers.sh" blue

# ---------------------------------------------------------------------------
# 5. No bash >= 5 and no nix is exit 3, not a silent run under whatever is
# there. This is the arm that would have refused the macOS system bash.
d="$(sandbox oldbash)"
suite "$d" any <<'EOF'
#!/usr/bin/env bash
exit 0
EOF
mkdir -p "$work/fakebin"
cat > "$work/fakebin/bash" <<'EOF'
#!/bin/sh
case "$*" in *BASH_VERSINFO*) echo 3; exit 0 ;; esac
exit 0
EOF
chmod +x "$work/fakebin/bash"
# The runner is invoked through a REAL bash, so the fake one below is only
# what its own `command -v bash` probe finds -- not its interpreter.
# /usr/bin:/bin carries the utilities the runner itself needs and carries no
# nix, so the fake bash is the only candidate and the nix fallback is absent.
env PATH="$work/fakebin:/usr/bin:/bin" HOME="$HOME" \
  "${BASH:-bash}" "$d/checkers.sh" any > "$work/out" 2>&1
got=$?
[ "$got" = 3 ] && ok "an old bash with no nix is exit 3" \
               || bad "an old bash with no nix is exit 3" "exit $got, wanted 3"

# ---------------------------------------------------------------------------
# 6. A named suite that does not exist is a usage error, not a silent no-op.
d="$(sandbox missing)"
suite "$d" present <<'EOF'
#!/usr/bin/env bash
exit 0
EOF
expect "an unknown suite name is exit 4" 4 "$d/checkers.sh" absent

# ---------------------------------------------------------------------------
# 7. --list names every suite in the directory and nothing else.
d="$(sandbox listing)"
suite "$d" alpha <<'EOF'
#!/usr/bin/env bash
exit 0
EOF
suite "$d" beta <<'EOF'
#!/usr/bin/env bash
exit 0
EOF
"$d/checkers.sh" --list > "$work/out" 2>&1
listed="$(tr '\n' ' ' < "$work/out")"
[ "$listed" = "alpha beta " ] && ok "--list names exactly the suites present" \
  || bad "--list names exactly the suites present" "got [$listed]"

# A test RUNNER also ends in -test.sh. It is not a suite, and running it as
# one is how `scripts/node-test.sh` printed its usage inside a green gate.
printf '#!/usr/bin/env bash\nexit 4\n' > "$d/gamma-test.sh"
chmod +x "$d/gamma-test.sh"
"$d/checkers.sh" --list > "$work/out" 2>&1
listed="$(tr '\n' ' ' < "$work/out")"
[ "$listed" = "alpha beta " ] \
  && ok "an X-test.sh with no X beside it is not a suite" \
  || bad "an X-test.sh with no X beside it is not a suite" "got [$listed]"

printf '\ncheckers-test: %d passed, %d failed\n' "$pass" "$fail"
[ "$fail" -eq 0 ]