The new tester allows to play with the AT-capable TTY using the same code as
ModemManager itself.
$ sudo ./test/mmtty -d /dev/ttyHS0 --verbose
opening serial port '/dev/ttyHS0'...
(ttyHS0) opening serial port...
(ttyHS0): port attributes not fully set
(ttyHS0) device open count is 1 (open)
flashing serial port '/dev/ttyHS0'...
ready
> AT+GCAP
(ttyHS0): --> 'AT+GCAP<LF><CR>'
(ttyHS0): <-- '<CR><LF>+GCAP: +CGSM,+DS,+ES<CR><LF><CR><LF>OK<CR><LF>'
+GCAP: +CGSM,+DS,+ES
> AT+GMI
(ttyHS0): --> 'AT+GMI<LF><CR>'
(ttyHS0): <-- '<CR><LF>Option N.V.<CR><LF><CR><LF>OK<CR><LF>'
Option N.V.
> ^C
cancelling the main loop...
(ttyHS0) device open count is 0 (close)
(ttyHS0) closing serial port...
(ttyHS0) serial port closed
(ttyHS0) forced to close port
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