The TTCN is part of the ISO/IEC 9646 conformance-testing framework and is specially designed for the specification of tests of communication systems. The standard introduces the concept of abstract test suites (consisting of abstract test cases), a description of a set of test cases that should be executed for a system. The abstract tests are to be described using a formal language rather than informal language. TTCN is defined in order to describe the abstract test cases.
The reference of Abstract Syntax Notation (ASN.1) definitions from protocol specifications into TTCN ensures consistency between the information transferred in the system specification and test specification.
Abstract test suite consists of four parts,
Ø Suite Overview part
Ø Declarations part
Ø Constraints part
Ø Dynamic part
(a) Suites Overview part
The suite overview part is documentary feature comprised of indexes and page references. It contains table of contents and a description of the test suite, and its purpose is mainly to document the test suite to increase clarity and readability. The quick overview of the entire test suite is possible. The test suite overview consists of four tables:
· Test Suite Structure
· Test Case Index
· Test Step Index
· Default Index
(b) Declarations part
The declaration part is used for declaring types, variables, timers, PCO’s and test components. All the data types used in the test suite are declared in this section. The types can be TTCN or ASN.1 types. Declaring types in TTCN or ASN.1 is similar to type declarations in other programming language except that in TTCN or ASN.1 tables are used instead of files. The declarations part is concerned both with the definition of new (i.e. not predefined) data types and operations and the declaration of all the test suite components.
(c) Constraints Part
The constraints part is used for describing the values sent or received. The structured types PDUs and ASPs defined in the declarations part are used as models to describe the messages sent on PCO. The instances used for sending must be complete, but for receiving there is the possibility to define incomplete values using wildcards, ranges and lists. The constraint part contains the tables for all the ASP, PDU, structure and CM constraints both in the tabular form and the ASN.1.
(d) Dynamic Part
The actual tests are described in dynamic part. It contains all test cases, test steps, and default tables with test events and verdicts. The building blocks are test groups, test cases, test steps and test events. The dynamic part contains all the test cases, all the test steps in the test step library and the all the defaults in the default library.
Test Component
The test component comprises of the test group, test case, test events and test step.
Test event – is the smallest unit of test suite. It corresponds to sending and receiving of the messages and operations for manipulating timers.
Test step – grouping of test events, which is similar to subroutines and procedures in other programming languages.
Test case - fundamental building block in test suite. A test case tests particular feature or function in the implementation under test (IUT). Test case assigns a verdict depends on outcome of the test case.
Test group – grouping of test cases. The grouping can be done based on functionality or features. Test suite – highest level encompassing all the test components and serving as root of the tree.
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