1. Improving the
Embedded
Development
Process
Matt Fletcher, Developer
William Bereza, Co-founder
Atomic Object, LLC
{fletcher, bereza}@atomicobject.com
OSCON 2007 Room D137-138

2. About this presentation
- Test-driven development of embedded systems
- Target audience is developers
- Audience is familiar with test-driven
development (TDD)
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3. Atomic and Savant Automation
- Atomic Object develops custom software
- Savant Automation produces automated-guided vehicles
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4. Battery monitor board
- Monitors the onboard battery’s overall state of
charge
- Vehicle’s main computer decides when to charge or
get back to work
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5. Feature development
Choose a new feature
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6. Feature development
Develop a system test for it
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7. Feature development
See the system test fail
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8. Feature development
Create unit tests for a module
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9. Feature development
See the unit tests fail
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10. Feature development
Make the tests pass
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11. Feature development
Develop modules as needed
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12. Feature development
See system test pass
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13. Feature development
Choose the next feature...
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14. Example system tests
- Battery level output based on input voltages
- Battery level mode vs. diagnostic data mode
- Calibration commands adjust battery level values
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15. Matt Fletcher and William Bereza OSCON 2007 15

16. Battery voltage test
proves quot;the battery voltage reported via
CAN is correct.quot;
set_battery_voltage 51.0
verify_can_reports_battery_voltage 51.0
set_battery_voltage 2.0
verify_can_reports_battery_voltage 2.0
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17. Under the covers
set_battery_voltage 51.0
verify_can_reports_battery_voltage 51.0
def set_battery_voltage(voltage)
@minilab.write_analog(VOLTAGE_OUTPUT_PIN,
voltage / BATTERY_VOLTAGE_DIVIDER)
sleep 0.1
end
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18. Under the covers
set_battery_voltage 51.0
verify_can_reports_battery_voltage 51.0
def verify_can_reports_battery_voltage(voltage)
last_message = @pcan.receive_message
assert_in_delta(voltage / CAN_VOLTAGE_BIT_WEIGHT,
last_message.BatteryVoltage,
CAN_VOLTAGE_DELTA)
end
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19. Keys to system testing
- Test automation
- Choosing support hardware with command line
and programmatic interfaces
- Diligence. System test-first!
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20. Develop code unit test-first
- Interaction-based testing
- Modules are composed with delegates
- Tests compose the target module with mocks
- Composition is done at link time
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21. Rake
- Ruby make
- Automates building units and executables
- Easy injection of Ruby scripts into the build
system
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22. Argent
- Ruby inline code generation
- Finds and sets up tests
- Invoked against files by the build system
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23. Generated mocks
- Mocks created automatically
- Ruby script scans header file
- Creates mock header and source
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24. Generated mocks
- Regular expression used to parse functions
FUNC_MAGIC =/(w*s+)*(w+)s+(w+)s*(([^)]*))/
- Naming conventions dictate how to declare
functions and how to call mock functions
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25. Code to be mocked
MessageCreator.h
CANMessage MessageCreator_GetNextMessage(void)
MessageSender.h
void MessageSender_SendMessage(CANMessage message)
StatusOutputter.c
Needs to send the latest messages!
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26. Mock with return
MessageCreator.h
CANMessage MessageCreator_GetNextMessage(void)
MockMessageCreator.h
CANMessage MessageCreator_GetNextMessage(void)
void MessageCreator_GetNextMessage_Return(CANMessage toReturn)
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27. Mock expecting a value
MessageSender.h
void MessageSender_SendMessage(CANMessage message)
MockMessageSender.h
void MessageSender_SendMessage(CANMessage message)
void MessageSender_SendMessage_Expect(CANMessage message)
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28. The test!
static void testShouldSendTheNewestMessage(void)
{
CANMessage someMessage = {0x0b, 0x0e, 0x0e, 0x0f};
MessageCreator_GetNextMessage_Return(someMessage);
MessageSender_SendMessage_Expect(someMessage);
StatusOutputter_SendNewestMessage();
}
Mocks are automatically verified during tearDown
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29. The code!
void StatusOutputter_SendNewestMessage(void)
{
CANMessage newestMessage;
newestMessage = MessageCreator_GetNextMessage();
MessageSender_SendMessage(newestMessage);
}
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30. Continuous integration
- Automatically builds the system and runs tests on
check-in
- Build status is published to monitors throughout
the office
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31. Summary
- Automated system testing
- Automated unit testing
- Automated build system
- Continuous integration
- Ruby scripts and extensions played a key role!
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32. Embedded development - fun
Imagine frustated engineer vs. a productive pair
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33. Build your own tools
- Solve specific problems with custom tools
- Automate tedious processes
- Generate repetitive code
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34. Resources
- Rake
- rake.rubyforge.org
- Argent
- rubyforge.org/project/argent
- Minilab Ruby gem
- minilab.rubyforge.org
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35. Resources
- Atomic Object embedded
- www.atomicobject.com/pages/Embedded+Software
- papers
- Embedded System Conference 2007 demo project
- Agile Embedded Yahoo! group:
- tech.groups.yahoo.com/group/AgileEmbedded
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36. Questions?
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