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TTCN


TTCN (Tree and Tabular Combined Notation) is a special purpose notation to describe test suites [34]. TTCN is a language standardized by ISO for the specification of tests for communicating systems. TTCN has been developed within the framework of standardized conformance testing (ISO/IEC 9646).

With TTCN a test suite is specified. This is a collection of various test cases together with all the declarations and components it needs.

Each test case is described as an event tree. The tree is represented as an indented list in a table. The indentation represents progression with respect to time. See Example 644.

Example 644 : A TTCN test case

    Behavior Description               Constraint        Verdict

1   DuToEnv? Display                   Enter_Card

2    EnvToDu! Card                     Card1

3     DuToEnv? Display                 Enter_Code

4      EnvToDu! Digit                  digit1

5       EnvToDu! Digit                 digit3

6        EnvToDu! Digit                digit5

7         EnvToDu! Digit               digit7

8          DuToEnv? Unlock             nopar

9           EnvToDu! Open              nopar

10           DuToEnv? Display          Please_Enter

11            EnvToDu! Close           nopar

12             DuToEnv? Lock           nopar

13              DuToEnv? Display       Enter_Card        PASS

14        EnvToDu! Digit               digit1

15         DuToEnv? Display            WrongCode

16          DuToEnv? Display           Enter_Card        PASS


Each line consists of a line number, a statement, a constraint reference and a mandatory verdict. A statement can be:

The event statements are statements that can be successful dependent on the occurrence of a certain event, either:

The action statements will always execute and will therefore always be successful:

A qualifier is simply an expression that must be true if an event should match or an action should be performed.

In TTCN, the communication is asynchronous. The implementation under test, IUT, communicates with the environment via points of control and observation, PCOs. The interaction occurs at PCOs and are described by protocol data units, PDUs, embedded in abstract service primitives, ASPs.

At line 1 in s above, the ASP Display occurs at the PCO DuToEnv. The constraint Enter_Card determines exactly which ASP value is to be received.

The leaves in the tree are usually assigned a verdict.


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