1. TTCN Overview
Ishwar

2. Overview of the Presentation
General wireless test systems
Why TTCN ??
Introduction to TTCN
Deeper into TTCN
How TTCN fits in our system
Versions of TTCN
Advantages and Disadvantages of TTCN
Questions ??

3. Expect to Learn What is TTCN and Why it is needed .. Brief about TTCN
Protocol system simulated using TTCN
How our test bench looks for DP and CP
Typical TTCN test case
Adv n disadv of TTCN

4. General Wireless system
CHAPTER I
General Wireless system

5. Typical Test system system
System Under Test (SUT)
Test System (TS)
Implementation Under Test (IUT)
tester

6. Typical wireless system
Layer S
Layer S SP
Service provided
SAP SP
Layer T
PDU
Layer T
Service used
Layer N
Layer N
SP : Service Primitive
SAP : Service Access Point
PDU : Protocol Data Unit

7. Some Acronyms Used often
Upper Tester
ASP: Abstract Service Primitive
PCO: Point of Control and Observation
IUT: Implementation Under Test
PDU: Protocol Data Unit
Tester: Test script written in TTCN
TTCN: Tree and Tabular Combined Notation
(TTCN-2)
ASP
ASP
PDU
IUT
ASP
ASP
Lower Tester

8. Typical Test system System Under Test (SUT) Test System (TS)
Test Co-ordination
Procedures (TCP)
Upper Tester
Lower Tester
ASPs
PCO
IUT
PDU
ASPs
PCO
Lower level service provider

9. Testing Process … Standard protocol specification test generation
Abstract test suite
TTCN
Test selection and
test implementation
Protocol implementation
Executable test suite
System
Under
Test
IUT
Tester

10. CHAPTER II
Why TTCN ??

11. Ideal Test Language Features
Implementation Independent:
Test case writer should not bother about implementation details. Assuming black box system tester should able to write the test cases.
Off-the-shelf test suites:
Because of above property so many ready made test suites will be available which could be readily usable (Anite)
Test case reusability:
Test case should be reusable. By this we can build complex test cases and from simples cases.
Dynamic configuration :
Tester should be able to decide test cases to be run and configurations dynamically.

12. Cont
SDL and ASN.1:
should supports SDL and ASN.1 representations as most of wireless systems use this representation.
Formalized description:
Formalized notation for description of test cases.
AND TTCN has all these qualities …

13. CHAPTER III
Introduction to TTCN

14. TTCN History
TTCN: Tree and Tabular Combined Notation
Versions 1 and 2 developed by ISO SC21 WG3 ( ) as part 3 of the ISO/IEC 9646 (ITU-T X.292) conformance testing methodology and framework
Latest update by ETSI in TR (TTCN-2++)
Version 3 (TTCN-3) developed by ETSI TC MTS ( )
Specialist Task Forces STF 133, 156 and 187

15. TTCN Language Syntax
The TTCN language syntax is very much similar to C++/Java.
- Provides all normal programming language constructs like
functions, if-else statements, for statement, while statement, dowhile
statement, goto statement.
TTCN has constructs specifically for test case specification and
evaluating the result of the execution of test cases on the SUT.
alt: allows alternates for the execution of test case.
template: allows defining of template to verify the contents of the data of the messages receive
ports: to specify the communication points between components as well as the SUT.
send and receive: send and receive operations on ports to send and
receive messages on the port
setverdict: setverdict sets the verdict for the scope in which it is

16. Priority of alternative
Tree notation .. A
Priority of alternative or A B E B C or or D C D F E or F G H G
Time H

17. Test Case Dynamic Behaviour
Tabular Notation
Test Case Dynamic Behaviour
Test Case Name: Basic_Connect
Group: Basic Telephone Calls
Purpose: Check that a normal Basic Call Connection can be established
Configuration:
Default:
Comments: Simple case Nr
1 Line ! OffHook
2 Line ? DialTone
Line ! Digits Call Subscr2
Line ? CallTone
Line ? LineConnect ConnSubscr2
Line ! OnHook Pass
Line ? BusyTone Busy B
Line ! DropHook Inconclusive
9 Line ? NoTone Fail
Label Dynamic Behaviour Constraints ref Verdict Comments

18. Forms of TTCN Suitable for Human Readability. For electronic exchange
Graphical Form (.GR)
Suitable for Human Readability.
Easily Understandable
Machine Process able form (.MP)
For electronic exchange
Suitable for automatic processing
Useful for export and imports

19. CHAPTER IV
Deeper into TTCN

20. On TTCN
Statements: A sequence of one or more statements, together with the indentation information, in a single behavior line is called a statement line. And they can be split into 3 types:
EVENTS
ACTIONS
QUALIFIERS

21. Cont … Actions: Always happens successfully .. (!)
SEND
ASSIGNMENT_LIST
TIMER_OPERATION
GO TO
Events: Waiting for response (Success/Fail/Inc).. (?)
RECIEVE
OTHERWISE
TIMEOUT
Qualifiers: No event can match, nor can any action be executed unless the qualifier included in the statement line evaluates to TRUE
BOOLEAN_EXPRESSION

23. TTCN Terminology Following are the words that are frequently used.
PCO, CP, CM, ASP, PDU, Constraints, Test Step, Test Case, Test Suite,Default,Otherwise etc..
Test Suite can be divided into
Static Part: Valued are filled Statically. Consists of Test case overview, Declaration and Constraint Parts.
Dynamic Part: Value and order is decided at the run time.
It consists of Test step, test case and default library.
- Test Suite Overview
- Declaration Part
- Constraint Part
- Dynamic Part

24. How TTCN fits in our system
CHAPTER V
How TTCN fits in our system

25. Test bench
Module in UMTS AS (like PDCP,RLC,RRCDC) implemented with SDL and C.
Routines implemented in C
Decision making and Signal handling implemented in SDL.
All C routines are called from SDL
TTCN interacts with SDL Test System.
User interacts with TTCN

26. Broad view of Test bench
System Under Test (SUT)
SDL TS
SDL+C
TTCN
IUT
(SDL+C)
tester

27. Typical Example … RABM/PDCP
Test
Cases
(TTCN) SM
RABMPDCP
(SDL+C)
GMM
TESTER
RRC
IPR
RLC
(SDL+C)

28. RABM/PDCP SDL Process

29. RABM/PDCP TTCN SDL Stub processes

30. High level view – PDCP test bench

31. Cont… Consider Example of PDCP
PDCP interacts with SM,GMM and RRCDC in control plane.
PDCP interacts with IPR and RLC in data plane.
To Test PDCP, we simulate all these modules in SDL
SDL systems for PDCP has BLOCKS RABMPDCP and RABMPDCP_TTCN
Since PDCP is implemented as one process it has one process.
Block RABMPDCP is module implementation which goes into product.
RABMPDCP_TTCN is Test Bench to test PDCP module.
It has 5 processes for 5 modules to which it interacts with namely SM,GMM,RRC,IPR and RLC

32. Test Benches of DP and CP
For Data Plane Modules: Its very difficult decode the data sent by the DP modules. To avoid decoding of the data by the test system loop back mechanism is used. Data in UL is looped back as Data in the DL. Then the validation of data is done.
For Control Plane Modules: For CP modules loop back mechanism is not used as its only controlling signals that are exchanged.

33. Data movement in Test Bench-DP
Test System
System Under Test (SUT)
PDCP UL
IPR IN
Validate
data
OUT
RLC
TTCN DL
SDL

34. Signal movement in Test Bench-CP
Test System
System Under Test (SUT)
GMM IN
Send
Stimulus
RRCDC
Check
response SM
OUT
SDL
TTCN

35. Use case for NSAPI Activation

36. TTCN Test case for above Use Case

37. Port.send(Stimulus) Port SUT Port.receive(Response) Stimulate SUT
Channel_rabmpdcp ? Deactivate_Cnf
Channel_rabmpdcp !Deactivate_Req
SUT
Port
SUT: System Under Test
Port: Formally specified system interface
Stimulate SUT
Compare observed response with expected response
Assign verdict
Channel_rabmpdcp
PDCP

38. Design of Good Test case
Following are few tips to write sound test case
Structures,ASPs,PDUs and Test steps should be readily reusable which is possible by parameterization.
Constraints name should reflect the its derivatives and direction etc.
Default Clause should be designed such a way it should capture all the errors and proper action for the error.
Test case should contain Preamble and Postamble to bring system from Idle and take it to Idle.

39. CHAPTER VI
Adv and Disadv of TTCN

40. Advantages of TTCN Signals used to exchange data and PID info
Tests written in TTCN are independent of:
Test Methods
Layers
Protocols
Test Tools
TTCN provides powerful means for modularising and parameterisation of test cases
TTCN-3 core is a textual format (like .mp in TCN-2) that allows for:
Electronic storage
Exchange between different tools
Conversion from/to other formats (.ps, .xml, .html)
Translation into executable code

41. Disadvantages of TTCN Data Writing a compiler for TTCN is difficult
TTCN tools are expensive
Templates to define each bit -> many test cases!
Cannot express hard real-time constraints
A lot of code needs to be written before you can actually do something useful

42. Questions ??