One of the core Agile Practices is Test-Driven Development (TDD). For most software engineers TDD challenges the traditional approach to software development and testing (test-after-construction). TDD changes this model by using a Test-First approach.
However, almost all current books and training on TDD ignore the challenges of applying it in an embedded systems environment. Aspects such as testing on the target, hardware dependency and managing both host and cross-compiler toolchains are generally ignored or over-simplified. In addition almost all are based on an object-oriented language, such as Java or C++ rather than C.
The course covers testing embedded C software across host, emulated and target environments.
Attendees perform practical TDD exercises using both host (Linux / gcc) and cross-development (Cortex-M / arm-none-eabi-gcc) toolchains supported by a modern build system (SCons) and configuration management (Git) tools.
The course utilises the C based test framework Unity and CMock for test doubles.
- To understand the principles of Test-Driven Development
- How to select a suitable test framework for C development
- To identify the required toolset to support TDD beyond the test framework
- The boundary between host-based testing and target-based testing
- The challenges and pitfalls of applying TDD to an embedded system
Delegates will learn:
- How to practice Test-Driven Development
- The use of C based test harnesses for embedded systems
- API and Integration testing using test doubles (CMock)
- The importance of architectural design to practical TDD
- What TDD doesn't address
- Attendees should have a good working knowledge of the C language.
- Understand the build process (preprocessor-compiler-linker-executable)
Who should attend:
The course is designed for software engineers working on an embedded C project.
The target audience is engineers working in, or looking to move to, an Agile project environment (e.g. Scrum) and who want practical experience of using TDD for a real embedded system.
- Delegate manual
- Delegate workbook
- Delegate bootable Linux datakey with all tools installed
Attendees perform a mixture of hands-on programming for both host and embedded targets.
The initial exercises show how to test embedded code on a host system (Linux), then move to emulator based testing (QEMU) and the final exercises include integration testing so as to apply TDD to a target hardware.
Approximately 50% of the course is given over to practical work.
The host code is developed on Linux using GCC and Scons supported by Git versioning. The embedded code is targeted at an ARM Cortex-M based MCU using arm-none-eabi-gcc. This combination gives attendees a real sense of the challenges of applying TDD to embedded application development.
Agile Techniques and TDD
- Where does TDD fit in?
- Agile onion
- Embedded TDD Strategy
- Unit tests
- Red-Green-Refactor (RGR)
- 3 rules of TDD
- Failing tests
- Tests are FIRST
- File organisation
- Failure based tests
- Breaking encapsulation (Inspecting privates)
- Running a subset of tests
- Testing vs. Test Driving
- Abstraction and encapsulation
- What can we learn from OO's SOLID Principles
- Simple test doubles
- Dependency Challenges
- UML Sequence Diagrams
Advanced Test Doubles
- Getting Mocks in place
- Design and change
- Walking skeleton
- Importance of architecture
- Version control and branching (git-workflow)
- Building for the target
- Testing using emulation (QEMU)
- Testing on the target
- Containers and Docker
- Continuous Integration (CI) (Jenkins / Bamboo)
- Cloud-based CI builds (Codeship, Travis-CI, Bitbucket)
- non-functional tests
- test anti-patterns
- Legacy Code Change Policy
TDD and Threading
- GPOS threading vs. RTOS tasking
- Separate threading logic from application logic