A. Mednonogov / Helsinki University of Technology / Conformance Testing of CORBA Services Using TTCN...

A. Mednonogov / Helsinki University of Technology / Conformance Testing of CORBA Services Using TTCN

/ 6.3.2000 /

Conformance Testing of CORBA Services Conformance Testing of CORBA Services using Tree and Tabular Combined Notationusing Tree and Tabular Combined Notation

Alexey MednonogovAlexey Mednonogov

Helsinki University of TechnologyHelsinki University of TechnologyTelecommunications Software and Multimedia Laboratory

March 2000, Espoo FINLAND

[email protected]


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Applications and TechniquesApplications and Techniques

Common Object Request Broker Architecture Middleware architecture for transparent communication in

heterogeneous environment (platform, language, location) Interoperable, robust, high-performance solutions Seamless interconnection of multi-vendor services

Conformance testing of CORBA using TTCN TTCN is a mature standardized framework for reusable

and automated testing of telecommunication systems Key success factor for ensuring reliability of distributed

Internet-based CORBA services and applications


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Object Management ArchitectureObject Management Architecture

CORBA is the communications heart of OMA Reference Model

ORB is a low-level subsystem responsible for transparent communication of objects

CORBAservices define system interfaces complementing the basic functionality of ORB

CORBAfacilities provide standard frameworks for defining universal rules of engagement for CORBA-based collaborating objects

Object Management ArchitectureReference Model


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CORBA Middleware ArchitectureCORBA Middleware Architecture Interface Definition Language

(IDL) acts as a primary contract between servers and clients, abstracting from the details of implementation, location in the network and the platform used

A client can introspect contents of Interface Repository (IFR) to find out which requests can be processed by a specific server and what data types are used

A server advertises its presence to clients by its Interoperable Object Reference (IOR)

OMG Common Object RequestBroker Architecture


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Conformance Testing ArchitectureConformance Testing Architecture


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CORBA Services Testing MethodologyCORBA Services Testing Methodology

Application-level CORBA clients and servers are being tested using remote test method in a single-party testing context (SPyT)

Low-level ORB protocols (GIOP/IIOP) and all other ORB components are assumed to be functioning properly

CORBA/TTCN gateway exploits DII, DSI & IFR to convert TTCN ASP to dynamic request / response and vice versa

As SUT cannot distinguish whether static or dynamic invocation scheme has been used, the implementation details of test environment are completely transparent from SUT perspective


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IDL/TTCN Mapping: OverviewIDL/TTCN Mapping: Overview

IDL-to-TTCN Mapping Rules in a Nutshell

CORBA IDL entity TTCN entity

Instance of IDL interface(client or server object)

PCO declaration

IDL operation declarationA pair of ASPs(pCALL_… and

pREPLY_…)

Actual operation call A pair of TTCN constraints

IDL data types ASN.1 data types

IDL attribute declaration [The same as for operations]

IDL exception declaration Exception ASP (pRAISE)

IDL name resolution andinheritance mechanism

[Additional arrangementsare unnecessary]

Related work of GMD FOKUS & JIDM (NMF and X/Open) shall be acknowledged (basic concepts for mapping IDL operations, type definitions etc. to TTCN language)


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IDL/TTCN Mapping: DetailsIDL/TTCN Mapping: Details

“Bit stuffing” concept is used for mapping IDL compound identifiers to a single TTCN identifier (symbolic chain “_i” acts as a separator and all “_” characters are duplicated, e.g. IDL “ModA_::_ModB::IntC” TTCN “PCO1_iModA___i__ModB_iIntC”)

CALL_ID field is introduced into every Exception, Call & Reply ASP to uniquely identify operation calls

Several forms of Registration ASP are defined for binding a specific TTCN PCO with CORBA client or server object

Our mapping allows catching group of exceptions defined within one IDL module/interface in one TTCN constraint


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IDL/TTCN Mapping: Data TypesIDL/TTCN Mapping: Data Types

In most cases, IDL data types are naturally mapped to ASN.1 types without complications

Mapping for IDL “union” shall include information about exact value of discriminator

IDL “any” type is a real challenge!


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CORBA/TTCN Gateway: OverviewCORBA/TTCN Gateway: Overview

Acts as an intermediary between Test System and SUT

The gateway itself is a CORBA-based Java application (ORBacus from OOC Inc. + OpenTTCN from OES Oy)

Distributed and interpreted nature of the test environment speeds up design of Abstract Test Suite (ATS), as well as facilitates testing in multi-party context (concurrent TTCN)

Relatively low performance of Java language is not of crucial importance, as performance measurements in conformance testing are not usually involved


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CORBA/TTCN Gateway: ArchitectureCORBA/TTCN Gateway: Architecture

Builder, Visitor & Adapter design patterns are used

Visitor introspects ASP coming from the test environment

Builder constructs ASP either from server response or from client operation call

Adapter performs a technical conversion of information from IFR into internal format

Asynchronous mode of DII is used, what allows design of concurrent test suites or even simultaneous execution of several test suites served by one gateway component


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Testing Gateway FunctionalityTesting Gateway Functionality

Two groups of test cases, 9 test cases in each group

One group for testing CORBA servers, another one for testing CORBA clients

A minimum set of tests of gateway states

Test Case ID Gateway Functionality Under Test

PrototypeInvocation of server operations,accepting client requests

Primitive IDL primitive data types

Oneway IDL oneway operations

Struct IDL structured data types

Choice IDL "union" data type

Context Operation "context" clause

Concurrent Concurrent operation calls

ExceptionHandling of user-defined &system exceptions

Abnormal Invalid and inopportune ASPs


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Test Session ExampleTest Session ExampleTest Case

Test Case ID: tcINVOKE_COUNT

Test Group Reference: Operations/

Test Case Purpose:To test that after CORBA server object is registeredby its IOR and "increment" operation is invoked, itreturns the argument of the operation incrementedby one.

N L Behaviour Description Constraint Ref V C

1 PCO1_iArithmetic_iCount !pSREG_IOR START tSREG

cSREG_IOR(xIOR1_iArithmetic_iCount)

2 PCO1_iArithmetic_iCount ?pRAISE

c1RAISE_iGatewayException_iRecoverable_iGeneral

3 PCO1_iArithmetic_iCount !pCALL_iArithmetic_iCount_iincrement START tREPLY

c1CALL1_iArithmetic_iCount_iincrement

4 PCO1_iArithmetic_iCount ?pREPLY_iArithmetic_iCount_iincrement

c1REPLY1_iArithmetic_iCount_iincrement

P

5 ? TIMEOUT tREPLY F

6 PCO1_iArithmetic_iCount ?OTHERWISE

F

7 ? TIMEOUT tSREG F

8 PCO1_iArithmetic_iCount ?OTHERWISE

F

Two typical stages of testing CORBA service:

registering a CORBA object (pCREG_IOR)

issuing (or accepting) actual operation calls

IOR used for binding a PCO with CORBA server is supplied to ATS in form of PIXIT parameter


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ConclusionsConclusions

TTCN framework facilitates practical testing of active service components (servers), as it provides formal and standardized means for reusable & automated testing of telecom systems

Yet, TTCN does not show up enough flexibility in emulating a full-scale functionality of a typical CORBA servant, making TTCN-oriented processing of requests coming from reactive components (clients) look relatively awkward

If SUT mostly contains active parts (which is normally the case in testing CORBA services), then TTCN framework shall undoubtedly be preferred

A. Mednonogov / Helsinki University of Technology / Conformance Testing of CORBA Services Using TTCN...

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