test iocmd.tf-24.16 {chan write, note the background flush setup by close due to the EAGAIN leaving data in buffers.} -match glob -setup {
    set res {}
    proc foo {args} {
	oninit; onfinal; track
	# Note: The EAGAIN signals that the channel cannot accept
	# write requests right now, this in turn causes the IO core to
	# request the generation of writable events (see expected
	# result below, and compare to case 24.14 above).
	error EAGAIN
    }
    set c [chan create {r w} foo]
} -body {
    notes [inthread $c {
	note [puts -nonewline $c ABC ; flush $c]
	close $c
	notes
    } c]
    # Replace handler with all-tracking one which doesn't error.
    # This will tell us if a write-due-flush is there.
    proc foo {args} { note BG ; track }
    # Flush (sic!) the event-queue to capture the write from a
    # BG-flush.
    update
    set res
} -cleanup {
    rename foo {}
    unset res
} -result {{write rc* ABC} {watch rc* write} {} BG {write rc* ABC}} \
    -constraints {testchannel testthread}