diff --git a/test/debug-bind-mount.t b/test/debug-bind-mount.t
new file mode 100755
index 0000000..c0be787
--- /dev/null
+++ b/test/debug-bind-mount.t
@@ -0,0 +1,20 @@
+#!/usr/bin/env cram.sh
+
+[DO-NOT-MERGE] Debug bind mount environment
+
+Host /dev/shm state
+
+	$ findmnt /dev/shm 2>&1 || true
+	$ grep '/dev/shm\|/mnt' /proc/self/mountinfo || echo "no /dev/shm or /mnt in host mountinfo"
+
+Inside bst with bind mount: mountinfo lines for /dev/shm and /mnt
+
+	$ bst --mount /dev/shm,/mnt,none,bind sh -c 'grep "/dev/shm\|/mnt" /proc/self/mountinfo'
+
+Inside bst with bind mount: /proc/mounts lines for /dev/shm and /mnt
+
+	$ bst --mount /dev/shm,/mnt,none,bind sh -c 'grep "/dev/shm\|/mnt" /proc/mounts'
+
+The actual test assertion (should print OK if device IDs match)
+
+	$ bst --mount /dev/shm,/mnt,none,bind awk '/\/dev\/shm/ { shm=$3 } /\/mnt/ { mnt=$3 } END { printf "shm=%s mnt=%s => ", shm, mnt; if (shm == mnt) { print "OK" } else { print "KO" } }' /proc/self/mountinfo