I do some very simple LAPDm test.
Establishing link.
ms_to_bts_l1_cb: MS(us) -> BTS prim message
bts_to_ms_tx_cb: MS->BTS(us) message 25
BTS: Verifying CM request.

Confirming
lapdm_phsap_dequeue_prim(): got rc 0: Success
Took message from DCCH queue: L2 header size 3, L3 size 20, SAP 0x1000000, 0/0, Link 0x00
Message: [L2]> 01 73 41 [L3]> 05 24 31 03 50 18 93 08 29 47 80 00 00 00 00 80 2b 2b 2b 2b 
ms_to_bts_tx_cb: BTS->MS(us) message 6
MS: Verifying incoming primitive.

Sending back to MS
lapdm_phsap_dequeue_prim(): got rc 0: Success
Took message from DCCH queue: L2 header size 3, L3 size 20, SAP 0x1000000, 0/0, Link 0x00
Message: [L2]> 03 00 0d [L3]> 05 04 0d 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 
ms_to_bts_tx_cb: BTS->MS(us) message 12
MS: Verifying incoming MM message: 3
ms_to_bts_l1_cb: MS(us) -> BTS prim message
lapdm_phsap_dequeue_prim(): got rc -19: No such device

Sending back to BTS
ms_to_bts_l1_cb: MS(us) -> BTS prim message
bts_to_ms_tx_cb: MS->BTS(us) message 14
BTS: Verifying dummy message.
lapdm_phsap_dequeue_prim(): got rc 0: Success
MSGB: L3 is undefined
Took message from DCCH queue: L2 header size 23, L3 size 0, SAP 0x1000000, 0/0, Link 0x00
Message: [L2]> 01 21 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 
lapdm_phsap_dequeue_prim(): got rc -19: No such device
lapdm_phsap_dequeue_prim(): got rc -19: No such device
I test RF channel release of an unestablished channel.
I test contention resultion by having two mobiles collide and first mobile repeating SABM.
bts_to_ms_tx_cb: MS->BTS(us) message 25
BTS: Verifying CM request.
lapdm_phsap_dequeue_prim(): got rc 0: Success
Took message from DCCH queue: L2 header size 3, L3 size 20, SAP 0x1000000, 0/0, Link 0x00
Message: [L2]> 01 73 41 [L3]> 05 24 31 03 50 18 93 08 29 47 80 00 00 00 00 80 2b 2b 2b 2b 
lapdm_phsap_dequeue_prim(): got rc -19: No such device
lapdm_phsap_dequeue_prim(): got rc 0: Success
Took message from DCCH queue: L2 header size 3, L3 size 20, SAP 0x1000000, 0/0, Link 0x00
Message: [L2]> 01 73 41 [L3]> 05 24 31 03 50 18 93 08 29 47 80 00 00 00 00 80 2b 2b 2b 2b 
I test RF channel establishment.
Testing SAPI3/SDCCH
lapdm_rslms_recvmsg(): got rc 0: Success
lapdm_phsap_dequeue_prim(): got rc 0: Success
Took message from DCCH queue: L2 header size 3, L3 size 20, SAP 0x1000000, 0/0, Link 0x03
Message: [L2]> 0f 3f 01 [L3]> 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 
lapdm_phsap_dequeue_prim(): got rc -19: No such device
lapdm_phsap_dequeue_prim(): got rc -19: No such device
Testing SAPI3/SACCH
lapdm_rslms_recvmsg(): got rc 0: Success
lapdm_phsap_dequeue_prim(): got rc -19: No such device
lapdm_phsap_dequeue_prim(): got rc 0: Success
Took message from ACCH queue: L2 header size 5, L3 size 18, SAP 0x1000000, 0/0, Link 0x43
Message: [L2]> 00 00 0f 3f 01 [L3]> 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 
lapdm_phsap_dequeue_prim(): got rc -19: No such device
lapdm_phsap_dequeue_prim(): got rc -19: No such device
I test if desync problems exist in LAPDm

Establishing SAPI=0
bts_to_ms_dummy_tx_cb: MS->BTS(us) message 25

Dumping queue:
00 00 17 [L2]> 01 73 41 [L3]> 05 24 31 03 50 18 93 08 29 47 80 00 00 00 00 80 

lapdm_phsap_dequeue_prim(): got rc 0: Success
Took message from DCCH queue: L2 header size 3, L3 size 20, SAP 0x1000000, 0/0, Link 0x00
Message: [L2]> 01 73 41 [L3]> 05 24 31 03 50 18 93 08 29 47 80 00 00 00 00 80 2b 2b 2b 2b 

Sending Classmark Change
bts_to_ms_dummy_tx_cb: MS->BTS(us) message 27

Dumping queue:
00 00 17 [L2]> 01 21 01 

lapdm_phsap_dequeue_prim(): got rc 0: Success
MSGB: L3 is undefined
Took message from DCCH queue: L2 header size 23, L3 size 0, SAP 0x1000000, 0/0, Link 0x00
Message: [L2]> 01 21 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 

Enqueueing Ciphering Mode Command

Dumping queue:
00 00 17 [L2]> 03 20 0d [L3]> 06 35 01 


Sending GPRS Suspend Request
bts_to_ms_dummy_tx_cb: MS->BTS(us) message 22

Dumping queue:
00 00 17 [L2]> 03 40 0d [L3]> 06 35 01 

lapdm_phsap_dequeue_prim(): got rc 0: Success
Took message from DCCH queue: L2 header size 3, L3 size 20, SAP 0x1000000, 0/0, Link 0x00
Message: [L2]> 03 40 0d [L3]> 06 35 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 

Sending Cipher Mode Complete
bts_to_ms_dummy_tx_cb: MS->BTS(us) message 11

Dumping queue:
00 00 17 [L2]> 01 61 01 

lapdm_phsap_dequeue_prim(): got rc 0: Success
MSGB: L3 is undefined
Took message from DCCH queue: L2 header size 23, L3 size 0, SAP 0x1000000, 0/0, Link 0x00
Message: [L2]> 01 61 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 

Establishing SAPI=3
bts_to_ms_dummy_tx_cb: MS->BTS(us) message 6

Dumping queue:

lapdm_phsap_dequeue_prim(): got rc 0: Success
Took message from DCCH queue: L2 header size 3, L3 size 20, SAP 0x1000000, 0/0, Link 0x03
Message: [L2]> 0d 73 01 [L3]> 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 

Sending CP-DATA

Dumping queue:

lapdm_phsap_dequeue_prim(): got rc 0: Success
MSGB: L3 is undefined
Took message from DCCH queue: L2 header size 23, L3 size 0, SAP 0x1000000, 0/0, Link 0x03
Message: [L2]> 0d 21 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 

=== I test SAPI0/SAPI3 prioritization ===

MS is establishing a SAPI=0 link
bts_to_ms_dummy_tx_cb: MS->BTS(us) message 22
BTS is establishing a SAPI=3 link
lapdm_phsap_dequeue_prim(): got rc 0: Success
Took message from DCCH queue: L2 header size 3, L3 size 20, SAP 0x1000000, 0/0, Link 0x00
Message: [L2]> 01 73 35 [L3]> 06 27 07 03 50 58 92 05 f4 44 59 ba 63 2b 2b 2b 2b 2b 2b 2b 
lapdm_phsap_dequeue_prim(): got rc 0: Success
Took message from DCCH queue: L2 header size 3, L3 size 20, SAP 0x1000000, 0/0, Link 0x03
Message: [L2]> 0f 3f 01 [L3]> 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 
Checking the func=UA message: OK
Checking the func=SABM message: OK

Checking whether the DCCH/SACCH queues are empty
lapdm_phsap_dequeue_prim(): got rc -19: No such device
lapdm_phsap_dequeue_prim(): got rc -19: No such device
Success.