1. Software Testing and Reliability Testing Real-Time Systems Aditya P. Mathur Purdue University May 19-23, 2003 @Guidant Corporation Minneapolis/St Paul, MN Graduate Assistants : Ramkumar Natarajan Baskar Sridharan Last update: April 17, 2003

2. Software Testing and Reliability  Aditya P. Mathur 2002 2 Learning objectives Issues in testing real-time systems Tools for testing real-time systems Methodology for testing real-time systems

3. Software Testing and Reliability  Aditya P. Mathur 2002 3 References Testing Embedded Systems, Do You have the GuTs for it?, Vincent Encontre, Rational June 2001, http://www.rational.com/products/whitepapers/final_encontre_testing.jsp CodeTest Vision for Embedded Software, Applied Microsystems Corporation, http://www.amc.com/products/codetest/. G-Cover Object Code Analyzer, Green Hills Software Inc., http://www.ghs.com/products/safety_critical/gcover.html DO-178B, http://www.rtca.org and http://www.windriver.com/products/html/do178b.html

4. Software Testing and Reliability  Aditya P. Mathur 2002 4 The RTCA DO-178B Guidelines The guidelines in DO-178B impose constraints on the software development process so that the resulting system is safe. The FAA’s DO-178B offers guidelines for the development of airborne systems equipment software. Most RTOS tool vendors have accepted the guidelines in DO- 178B and begun to offer tool support.

5. Software Testing and Reliability  Aditya P. Mathur 2002 5 Levels of Criticality-A, B Level A: Software with anomalous behavior, as shown by the system safety assessment process, would cause or contribute to a failure of system function resulting in a catastrophic failure condition for the aircraft. Level B: Software with anomalous behavior, as shown by the system safety assessment process, would cause or contribute to a failure of system function resulting in a hazardous/severe- major failure condition for the aircraft. Guidant products: Level A or B?

6. Software Testing and Reliability  Aditya P. Mathur 2002 6 Levels of Criticality-C, D, E Level C: Software with anomalous behavior, as shown by the system safety assessment process, would cause or contribute to a failure of system function resulting in a major failure condition for the aircraft. Level D: Software with anomalous behavior, as shown by the system safety assessment process, would cause or contribute to a failure of system function resulting in a minor failure condition for the aircraft. Level E: Software with anomalous behavior, as shown by the system safety assessment process, would cause or contribute to a failure of system function with no effect on aircraft operational capability or pilot workload.

7. Software Testing and Reliability  Aditya P. Mathur 2002 7 Guidelines Related to Testing Test Procedures are correct Compliance with Software Verification Plan Results are correct Test coverage of High-Level requirements Test coverage of Low-Level requirements Test coverage of object code Test coverage - Statement, Decision, and Modified condition/decision Test coverage - Data coupling and control coupling

8. Software Testing and Reliability  Aditya P. Mathur 2002 8 Issues in Testing Real-Time Systems Separation of development and execution platforms Variety of execution platforms (combinations of hardware and OS, e.g. Z80/QNX, Tornado/PowerPC) Tight resources and timing constraints Emerging quality and certification standards

9. Software Testing and Reliability  Aditya P. Mathur 2002 9 Test Methodology: Unit Testing Identify the module to be tested. This module becomes MuT. Prepare MuT for testing. Isolate the MuT from its environment. Make MuT an independently executable module by adding a stub and a test driver. stubMuT Test Driver Replaces the rest of the application Module under test Generate tests Test harness

10. Software Testing and Reliability  Aditya P. Mathur 2002 10 Issues in Unit Testing How to generate tests? What to observe inside MuT? Returned parameters Internal state such as values of global variables, coverage, control flow for verification against a UML sequence diagram, etc. How to observe? Use coverage tools or debuggers Insert probes When to stop testing?

11. Software Testing and Reliability  Aditya P. Mathur 2002 11 Test Methodology: Integration Testing Combine multiple MuT into a larger software component. Build a test harness. Look for the correctness of interactions amongst the various MuTs in the component. Again, UML sequence diagrams can be useful in validating the interactions against design.

12. Software Testing and Reliability  Aditya P. Mathur 2002 12 Test Methodology: System (Unit) Testing The MuT is now a complete software application. Test is executed under the RTOS. Communication amongst individual modules might be via the RTOS. The test driver could now be a simulator. The system needs to be brought to a desired initial state and then generate and send to the system a sequence of test messages. Observation is done using probes. The data so collected is analyzed on the host platform. Usually one does grey-box testing at this stage but more could be done.

13. Software Testing and Reliability  Aditya P. Mathur 2002 13 Test Methodology: System Integration Testing Integrate other software components of the end-application. These might be off-the-shelf components. Test is integrated system

14. Software Testing and Reliability  Aditya P. Mathur 2002 14 Test Methodology: System Validation Testing For overall embedded system, perform the following: Check if the system meets the end-user functional requirements. Perform non-functional testing. This includes load testing, robustness testing, and performance testing. Check for conformance with any inter-operability requirements.

15. Software Testing and Reliability  Aditya P. Mathur 2002 15 Run-time Analysis Source CompilerAssembler/LinkerExecutable Target platform RTA server GUI Analysis tools WindRiver and Agilent offer real-time trace tools that work with Agilent’s logic analyzers.

16. Software Testing and Reliability  Aditya P. Mathur 2002 16 Applicability of Test Techniques to Real-Time Systems All techniques for test data generation and coverage analysis covered in this course are applicable when testing real-time applications. Due to the embedded nature of such applications, one generally needs to use special tools that operate in a client- server mode; the server running on the host machine and the client on the target environment. The client provides data gathered during the execution of the embedded application and the server analyses and presents it to the tester.

17. Software Testing and Reliability  Aditya P. Mathur 2002 17 Tools for Testing Real Time Systems Rational: Test RealTime: code coverage; execution sequence, unit testing; integration testing, checking assertions for C++ classes; testing C threads, tasks, processes; evaluatin the UML model; requirement to test traceability; plug-in for mathworks Simulink. Applied Microsystems: CodeTest: A suite of several tools; performance measurement; tracing of execution history; finds memory leaks; code coverage measurement; supports QNX. Green Hills Software: G-Cover: Coverage analysis at the object code level; indirect source code coverage information. WindRiver: RTA: Detects memory leaks; identifies hot spots; per task profiling.

18. Software Testing and Reliability  Aditya P. Mathur 2002 18 Summary Issues in testing real-time systems Test tool architecture Test methodology