Add isolated kind dependency testbed

tests/kind/lib-test.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../.." && pwd)"
+source "$ROOT/tests/kind/lib.sh"
+
+if kube get namespaces >/dev/null 2>&1; then
+  printf 'kube helper unexpectedly reached a cluster without fixture setup\n' >&2
+  exit 1
+fi
+
+FIXTURE_LOCK_DIR="$RUNTIME/lock-test"
+FIXTURE_LOCK_PATH="$FIXTURE_LOCK_DIR/nuthatch-testbed-kind.lock"
+acquire_fixture_lock
+if XDG_RUNTIME_DIR="$FIXTURE_LOCK_DIR" bash -c \
+  'source "$1"; acquire_fixture_lock' _ "$ROOT/tests/kind/lib.sh" 9>&-; then
+  printf 'singleton fixture lock admitted a second worktree process\n' >&2
+  exit 1
+fi
+exec 9>&-
+
+printf 'fixture isolation tests passed\n'