close $f1
    after 500
    set f [open $path(test1)]
    lappend result [read $f]
    close $f
    set result
} "ready line1 line2 {done\n}"
test io-53.4 {CopyData: background write overflow} {stdio unix openpipe fileevent fcopy} {
    set big bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n
    variable x
    for {set x 0} {$x < 12} {incr x} {
	append big $big
    }
    file delete $path(pipe)
    set f1 [open $path(pipe) w]