Toggle filesystem test mode. Filesystem test mode, when turned on, prints out data corresponding to all the device reads and what values are being sent to the low-level routines. The format is `<partition-offset-sector, byte-offset, byte-length>' for high-level reads inside a partition, and `[disk-offset-sector]' for low-level sector requests from the disk. Filesystem test mode is turned off by any use of the install (see install) or testload (see testload) commands.