Feb 6, 2012

The book club of "Test Driven Development for Embedded C" started in Tokyo, Japan

The book club started today : )

Core members of the book club met at "TDD Boot Camp Tokyo for C++" in 2011. This was the event that embedded or game engineers got together and had a TDD practice.

At that time, I wrote my position paper like this: "I want to learn TDD for embedded software, so I want to hold a book club of Test Driven Development for Embedded C. Why don't you join? " To my delight, two engineers said to me that they would join. After I called for participants of this book club on Twitter, 10 engineers joined! That was how we started.

What is motivation of participants?

Participants are embedded software engineers of MFP, medical devices, communication devices, home electronics and etc. We have common point. We have legacy code, code without tests, in our projects and have a hard time of debugging. This is unpredictable activity.

To reduce time of debugging, to discovery bugs rapidly, we are paying attention to TDD.

What we read today

Today we read the first three chapters.

The first chapter "Test Driven Development" introduces what is TDD, purpose of TDD and benefits of TDD.

TDD is one of design techniques, so I can say that I do TDD to improve software design. But the biggest purpose of TDD is to prevent from bugs by getting quick feedback of test results and find mistake rapidly.

The second chapter "Test Driving Tools and Conventions" introduces Unity for C and CppUTest for C/C++ as testing frameworks that were introduced in this book.

CppUTest has a function to add tests into test suite automatically. This is very good for TDD. And it was developed with old function of C++ so that old compiles can compile it.

Unity doesn't have a function to add tests automatically but there is ruby script to do it. It is very convenient.

The third chapter "Starting a C Module " introduces the steps of TDD. We try practical example, LED driver. In this chapter, we can learn embedded software version of Dependency Injection. That is to put physical address of LED driver at runtime. With this way, we can separate software from hardware and we can get benefit to test without hardware.

What we didn't understand

We didn't understand following two points.

The first point. Can we design like this LED Driver example in real project? This example is OK because it is so simple. But in real project, dependency of hardware is so complicated. Changing physical address affects other hardware in some way. So we don't design like this.

Maybe, we can test only where we want to test without representing complicated hardware interaction. (I don't know how to do it)

Or, we don't test bottom of embedded software but focus on upper layer, which is hardware abstraction layer. That is easier to test than bottom layer. In this way, we can't test everything but we can reduce debugging time.

The second point is how we test mass of legacy code. If we need too much time before starting TDD, we lose motivation. To do TDD for real project, we need way to reduce initial cost and introduce TDD incrementally. The 13th chapter may introduce how to fight against legacy code. In near future, we can learn how to do it : )

How I felt after first time

We found that we have so many unknowns this time but we felt joyful that we got together at this book club. I want to say thank you to organizer of "TDD Boot Camp Tokyo for C++" and Mr. James W. Grenning. the author of Test Driven Development for Embedded C.

My job is to make the place that participants can learn a lot and enjoy : )

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