1.
Who is Lars Thorup?
● Software developer
● Web: C# and JavaScript
● Embedded C++ for several
devices using agile and
automated testing
● Coach: Teaching agile and
automated testing
● Advisor: Assesses software
projects and companies
● Founder and CEO of
BestBrains and ZeaLake

2.
Agenda
● What is automated testing?
● Unity, test framework for embedded C
● Code example
● Why should we write automated tests?
● Questions

3.
What is automated testing?
● Developers write test ● Automated execution of all
programs test programs

4.
The Unity testing framework
● Small memory footprint ● Many test functions
● ASSERT_TRUE
● Pure C ● FAIL
● ASSERT_EQUAL
● Optional tools to generate ● ASSERT_WITHIN
test runners automatically ● ASSERT_BITS
● ASSERT_NOT_NULL
● Alternatives in C++
● ASSERT_MEMORY
● CppUnit
● Google Test

5.
How do we handle dependencies?
● The flow example
● a flow sensor
● generates pulse counts proportional to actual flow
● calculate average flow rate with regular intervals
● The dependencies in the flow example
● the sensor creating the pulse interrupt
● recurring timer event
● thread safe counting
● Decouple the dependencies
● Pulse: provide a callback to the FlowSensor component
● Timer and Counting: inject components into the Flow component
● flow.c

6.
Dependencies, on device
main.c
Listen
GetRate
flowSensor.c flow.c
Pulse
GetTime
timerImpl.c
Increment
counterImpl.c

7.
Dependencies, in test
flowTest.c
Pulse
GetRate
flow.c SetTime
GetTime
timerStub.c
Increment
counterImpl.c

8.
Strategy for testing embedded software
● Continuous Integration
● Automate build and test execution
● On desktop, simulator and/or the device
● Break dependencies
● Hardware Abstraction Layer
● Simulate time measurements and timer events
● Standardize on frequently used stubs
● Use mock objects for testing protocols
● Dependency injection
● Link time, where possible
● Run time, using function pointers, where necessary

9.
Why should we write unit tests?
● Speed up development
● Because of all the things we no longer have to waste time on
● Test Driven Development vs Debug Later Programming
● Avoid piling up technical dept (manual testing, bug fixing)
● Typing code is not where the bottleneck is
● Find bugs faster
● Trivial bugs found immediately
● QA can do exploratory testing earlier and more extensively
● Prevent bugs from reappearing
● Never fix a bug until we have a failing test
● Improve the software design
● Loose coupling is required to write tests

10.
Links to further resources
● List of testing tools for C and C++
● http://www.opensourcetesting.org/unit_c.php
● Book
● http://pragprog.com/titles/jgade/test-driven-development-for-
embedded-c
● Experiement on the benefits of TDD
● http://www.infoq.com/news/2009/03/TDD-Improves-Quality
● Meetup groups
● http://www.meetup.com/Test-Driven-Developers-Bay-Area/

11.
Questions