Software Testing

In this project, the software of the LÜTZE DIOLINE20 products was tested to obtain a certification according to DIN EN 50128 for SSAS 2. This testing was done using TESSY, a tool to automate module and integration testing of embedded software.

DIOLINE20 is an I/O system for use on rail vehicles. The DIOLINE20 system is equipped with a netX 100 microcontroller, a derivative of the ARM microcontroller family. The software was written in C and was compiled using the GNU compiler for ARM (gcc) in a configuration provided by Hitex. The code was debugged on the actual hardware, using the JTAG debugger TantinoARM and HiTOP IDE software from Hitex. The software comprised of 24 C source modules, each incorporating about 10 C code functions.

The actual module testing was not done by LÜTZE but was outsourced to Hitex, a service which they are able to provide as part of their module testing services. Such an approach does not only  relieve the manufacturer from the testing effort, but also makes for independent testing by a third party. This also provided a review of the software specifications by Hitex, for ambiguities or omissions etc. The processes for distributed development and the testing were jointly developed by LÜTZE and Hitex. These processes were then subsequently integrated in the existing LÜTZE development process.

The testing took place at Hitex in Karlsruhe. More than 1500 test cases were specified, implemented and executed. The test case specifications were designed using the Classification Tree Method. This method is fully supported by TESSY, as TESSY has an integrated Classification Tree Editor (CTE) built into it.

Another requirement of DIN EN 50128 is to determine the test coverage for each tested module. The used test coverage measure was branch coverage. TESSY is able to measure branch coverage without additional effort. An overall branch coverage of 98.8% was reached eventually, with the remaining 1.2% being checked manually. LÜTZE also possesses a TESSY license. With this license, LÜTZE was able to reproduce the testing results at their facility. LÜTZE is now also able to do regression testing and to develop the test further on. The test cases were delivered from Hitex to LÜTZE after finalisation of the test service.

The module tests conducted by Hitex form an important part to obtain the required certification from the train manufacturer for which LÜTZE provided DIOLINE20.

Due to the good results and the excellent cooperation between LÜTZE and Hitex during the test service, Hitex is already working on the next LÜTZE project.