The document discusses test-driven development (TDD) for embedded systems, highlighting the challenges of integrating agile practices due to hardware constraints. It emphasizes the need for a structured testing strategy, continuous integration, and effective acceptance criteria to enhance the quality of software in an embedded context. Key insights include the necessity for experienced testers and the limitations posed by hardware development, which often hinders the adoption of lean methodologies.

1. Test Driven
Development of
Embedded Systems
Marcin Czenko
Martijn Gelens
Wim van de Goor
Agile Testing Days, 14 october 2009, Berlin

2. • Test Consultancy at VIIQ.
• Agile Test Team leader at Philips CareServant.
• 10 years of experience in the Testing Field (7 years
V-Model, 3 years Agile).
• Some experience with coding.
• Bachelor degree in Information Technics.
• Married to Jeanne, has a dog (Sasha) and 2 cats.
Martijn Gelens

3. • Currently, Philips Software Engineering Services,
MiPlaza, Software Designer.
• Ph.D. in Computer Security from University of
Twente, Enschede, The Netherlands.
• M.Sc. in Software Engineering at Warsaw University
of Technology.
• 7 years of experience as an embedded software
developer (SterKom (Poland) and freelancer).
• Modelling Languages: my master thesis + one year
internship at Institute National des
Télécomunications (INT), Evry, Cedex, France.
• Agile, test-invected since one year.
• Married to Beata and also has two cats (Mufasa and
Ursus).
Marcin Czenko, Ph.D.

4. Wim van de Goor
• Agile Software Team Leader at Philips Software
Engineering Services, Philips MiPlaza.
• 8 years experience with eXtreme Programming.
• Agile mentor and Coach.
• Advised us on Agile Principles.

5. Contents
• Agile Testing
What Do we want to do?
• Constraints
What can we do?
• Agile Embedded Testing
How do we test?
• Conclusions

6. What do we want ?
• Prerequisites
• Test Strategy
• Acceptance Criteria
• Continuous Integration
• Testing

7. Prerequisites
• Testing is integrated in the team's Way of
Working.
• Acceptance Criteria are defined, discussed and
explored beforehand.
• Test Driven Development.
• Continuous Build and Integration.
• Testing is structured (specify, verify, report).

8. Test Strategy
• Product risks and mitigation.
• Tester-role.
• Definition of Done.
• Quality gates.
• Testing is structured (specify,
verify, report).

9. Test Strategy (cont.)
• Deliverables from outside (also HW).
• Issue procedure and attendees.
• Reporting (test reports, PMI, ...).
• Emergency scenarios.

10. Test Strategy (cont.)
The test strategy is build around the iterations and
hardware deliveries.

11. Acceptance Criteria
• Defined upfront
• Based upon Quality Attributes; functionality,
usability, efficiency, maintainability, reliability,
portability, etc...
• Definition of Done:
Tested and accepted, Code reviewed, documents
written, yellow sticker on the note, ...
• Quality Gate:
Acceptance tests passed, smoke test passed, ...

12. Continuous Integration
Automate your:
• Build procedure.
• Release package creation.
• Deployment to simulator.
• Deployment to Board Support Package.

13. Continuous Integration

14. Continuous Integration

15. Test Driven Development
• Means: “Write unit tests
before code”.
• Integrate with your
Continuous Integration
environment.
• Automate the Acceptance
Tests.

16. This is your framework

17. Constraints

18. Light to Heavy
Light Heavy

19. Light
• No cross-compilation required.
• Usually mainstream OS (Windows/Linux).
• Wide range of testing/mocking
frameworks available.
• Standard hardware - no or very limited
hardware level programming required.
• No dependence on a particular vendor
(supplier).

20. Heavy
• Small memory (no OS), limited performance,
limited debugging possibilities.
• Limited cross–compilers: often only C, and
Embedded (Extended) C++ available.
• Vendor specific.
• Difficult to find a testing/mocking framework.
• Custom hardware (ramp-up).

21. Hardware design
challenges

22. Using Evaluation Boards

23. Getting There (1)

24. Getting There (2)

25. Getting There (3)

26. Getting
There (4)

27. Getting There (5)

28. Getting There (6)

29. Getting There (7)

30. Development Board
• Selecting the right board can be
challenging (expensive ?).
• Chip selection driven by the availability
of the right board.
• The board selection driven by the
availability of the BSP and OS.

31. Is there a more lean
solution ?

32. Are we lean ?

33. Queue 1

34. Queue 2

35. Queue 3

36. The effect on Agile
Principles
• Longer ramp-up time.
• Resistance to modify hardware
(introduces up-front design).
• Limited response to changes.
• Higher risk.

37. How to proceed ?
• Often we cannot remove queues &
batches in HW development (are we
going to be able doing so in any
predictable future ?).
• Reducing the queue size is also often not
an option.
• Is there a lean solution ?

38. Getting There (7)

39. Fix in between...

40. Fix in between...

41. How do we test ?
Our experiences

42. What do we need
• Testing Strategy.
• Hardware to work with.
• Tool chain (compiler).
• Testing Framework.
• Mocking Framework.

43. Compiler
ISO C++
ANSI C

44. Testing Framework
Keep it simple !
Do-It-Yourself !

45. Testing Framework (C)
• Many frameworks are simple ports of
the frameworks for PC-based
development.
• Increased stack consumption.
• Dynamic memory allocation.

46. CMock
• Easy to understand. Easy to customise.
Lightweight.
• Comes with Supporting Ruby-based
Mocking Framework.
• Ready For “Heavy Embedded” - tests
executed in batches.

47. Testing Frameworks (C++)
• Run-Time Type
Information
(RTTI).
• Exceptions.
• ISO C++ compiler
needed.
• Gnu or Microsoft
are preferred.

48. Testing Frameworks (C++)
• We could not find a framework that
compiles on GreenHills and WindRiver
C++ compilers (forget IAR Extended
Embedded C++).
• It was cheaper and more effective to
come with your own simple testing
frameworks.

49. yaffut
• Our choice for unit testing in C++.
• Just one header file.
• Not meant for embedded: needs RTTI,
and C++ exceptions.
• Easy to understand and customise. We
made an RTTI and Exception-free
version.

50. Mocking
• We did not succeed in using existing
frameworks. Our best candidate
GoogleMock does not even compile and
it is quite complex.
• Does it mean that no one is doing TDD
on embedded ? Probably not.

51. Mocking - way to go
• Think of your own framework.
• We needed three “evenings” to create
our own mocking framework.

52. Educate your customer

53. Educate your customer

54. Conclusions
• Agile in Heavy Embedded is a challenge: we cannot change it, but
we can understand it and try to reduce its impact on agile software
development.
• The tester should be experienced in working with hardware,
perhaps even more than a developer.
• There is no one way: what you can do depends on the constraints
you have (e.g. light to heavy).
• Hardware development is far from being lean - and there is not
that much we can change.
• Development and support tools are far behind the needs of the
agile teams.
• Let your agile testing framework grow with your code.

55. Conclusions
• Agile in Heavy Embedded is a challenge: we cannot change it, but
we can understand it and try to reduce its impact on agile software
development.
• The tester should be experienced in working with hardware,
perhaps even more than a developer.
• There is no one way: what you can do depends on the constraints
you have (e.g. light to heavy).
• Hardware development is far from being lean - and there is not
that much we can change.
• Development and support tools are far behind the needs of the
agile teams.
• Let your agile testing framework grow with your code.
Be agile.

56. Questions