Simulated Time for Testing Railway Interlockings with TTCN-3

Abstract

In this report, we first give an overview of software systems based on Vital Processor Interlocking (VPI). Interlockings guarantee safety of railway control systems, so testing these software systems is a key issue. We show why testing such systems with real time and scaled time is inefficient. We also provide a time semantics for simulated time that is more suitable for testing VPI's software. We provide a solution that allows simulated time for TTCN-3 test systems. TTCN-3 is a standard language for specifying and executing test suites. In the context of the TT-MEDAL project, TTCN-3 is applied to various domains, in particular to testing railway and automotive systems. TTCN-3 supports real-time and scaled-time testing but not simulatedtime testing. The solution is based on a distributed termination detection algorithm that we extend to provide the main ingredients of simulated time: idleness detection and correct time progress. We implemented our solution as a TTCN-3 module and several Java classes that can be reused for testing other systems that have characteristics similar to those of VPIs.

TTCN-3 for Distributed Testing Embedded Software

“…In [1] we proposed host-based testing with simulated time for non-distributed applications. The solution provided in this paper is suitable for distributed testing.…”

“…That also makes TTCN-3 particularly beneficial for testing modern embedded systems. TTCN-3 has already been successfully applied to test embedded systems not only in telecommunication but also in automotive and railway domains [8,1].…”

“…In [1] we proposed host-based testing with simulated time for non-distributed applications. Implementing simulated time on the level of TTCN-3 specifications, this solution was not scalable for distributed testing and led to developing test suites only suitable for testing with "simulated time".…”

Simulated time for host‐based testing with TTCN‐3

“…Receiving an IDLE message from the PA i (l. 7) results in changing the status-variable IDLEPA to true and updating the local counters TRISENTSAPA and TRIENQDSAPA by the number of messages sent, TRISENT, and the number of messages enqueued, TRIENQD, by the PA i , respectively (l. [8][9][10].…”

“…TTCN-3 interfaces provide support for distributed testing, which makes TTCN-3 particularly beneficial for testing embedded systems. TTCN-3 has already been successfully applied to the testing of embedded systems not only in telecommunication but also in automotive and railway domains [7,8] TTCN-3 with different time semantics [3]. Implementing simulated time using existing TTCN-3 interfaces is, however, not straightforward.…”