Test Driven Development of

Embedded SystemsMarcin CzenkoMartijn Gelens

Wim van de Goor

Agile Testing Days, 14 october 2009, Berlin

• 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

• 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.

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.

Contents• Agile Testing

What Do we want to do?• Constraints

What can we do?• Agile Embedded Testing

How do we test?• Conclusions

What do we want ?

• Prerequisites • Test Strategy • Acceptance Criteria • Continuous Integration • Testing

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).

Test Strategy

• Product risks and mitigation.

• Tester-role.

• Definition of Done.

• Quality gates.

• Testing is structured (specify, verify, report).

Test Strategy (cont.)

• Deliverables from outside (also HW).

• Issue procedure and attendees.

• Reporting (test reports, PMI, ...).

• Emergency scenarios.

Test Strategy (cont.)

The test strategy is build around the iterations and hardware deliveries.

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, ...

Continuous Integration

Automate your:

• Build procedure.

• Release package creation.

• Deployment to simulator.

• Deployment to Board Support Package.

Continuous Integration

Continuous Integration

Test Driven Development

• Means: “Write unit tests before code”.

• Integrate with your Continuous Integration environment.

• Automate the Acceptance Tests.

This is your framework

Constraints

Light to HeavyLight Heavy

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).

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).

Hardware design challenges

Using Evaluation Boards

Getting There (1)

Getting There (2)

Getting There (3)

Getting There (4)

Getting There (5)

Getting There (6)

Getting There (7)

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.

Is there a more lean solution ?

Are we lean ?

Queue 1

Queue 2

Queue 3

The effect on Agile Principles

• Longer ramp-up time.

• Resistance to modify hardware (introduces up-front design).

• Limited response to changes.

• Higher risk.

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 ?

Getting There (7)

Fix in between...

Fix in between...

How do we test ?

Our experiences

What do we need

• Testing Strategy.

• Hardware to work with.

• Tool chain (compiler).

• Testing Framework.

• Mocking Framework.

Compiler

ISO C++

ANSI C

Testing Framework

Keep it simple !

Do-It-Yourself !

Testing Framework (C)

• Many frameworks are simple ports of the frameworks for PC-based development.

• Increased stack consumption.

• Dynamic memory allocation.

CMock

• Easy to understand. Easy to customise. Lightweight.

• Comes with Supporting Ruby-based Mocking Framework.

• Ready For “Heavy Embedded” - tests executed in batches.

Testing Frameworks (C++)• Run-Time Type

Information (RTTI).

• Exceptions.

• ISO C++ compiler needed.

• Gnu or Microsoft are preferred.

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.

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.

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.

Mocking - way to go

• Think of your own framework.

• We needed three “evenings” to create our own mocking framework.

Educate your customer

Educate your customer

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.

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.

Questions