Table Of ContentTest-Driven Development with C++
A simple guide to writing bug-free Agile code
Abdul Wahid Tanner
BIRMINGHAM—MUMBAI
Test-Driven Development with C++
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Focus on constant improvement
– Abdul Wahid Tanner
Contributors
About the author
I'm Abdul Wahid Tanner and have been programming C++ since 1992 and teaching others how to
code for almost as long. I first became interested in TDD around 2005 and decided to implement
a board game that I liked playing using strict TDD. At the time, I was using C# and a test framework
that was able to find and run the tests. It wasn't until about 2014 that I decided to see whether I could
use C++ and TDD together. There were many choices for tools that helped run C++ tests, but they
were big and full of features. I wanted something small and simple, so I wrote a unit test library in
about 650 lines of code. The code in this book is a complete and better rewrite of that early code.
I hope you find the code in this book useful and decide to use it in your projects. However, even if
you decide to use one of the commercial tools, you should still benefit from the understanding that
this book provides about how the tools work and how to follow the TDD process.
About the reviewer
Serban Stoenescu is a software developer specializing in C++. He is currently working for Everseen
on some projects that require OpenCV and some machine learning. In the past he has worked for
SkAD Labs on a CAD project with OpenCASCADE, Atigeo on Big Data projects in Java, and Alcatel-
Lucent (now part of Nokia). At Alcatel-Lucent, he was also a trainer, teaching Rational ROSE. He
is the co-author of “Towards the Impact of Design Flaws on the Resources Used by an Application”,
a paper at ARMS-CC 2014. Currently, he is also a Udemy instructor, his most popular course being
“C++ Unit Testing: Google Test and Google Mock”. His other courses are “CMake from Zero to Hero”
and “C++ Machine Learning Algorithms Inspired by Nature”.
Table of Contents
Preface xiii
Part 1: Testing MVP
1
Desired Test Declaration 3
Technical requirements 3 How can we use C++ to write tests? 11
What do we want tests to do for us? 4 How will the first test be used? 15
What should a test look like? 5 Summary 18
What information does a test need? 6
2
Test Results 19
Technical requirements 19 Summarizing the results 28
Reporting a single test result 20 Redirecting the output results 31
Enhancing the test declaration to Summary 33
support multiple tests 25
3
The TDD Process 35
Technical requirements 35 Enhancing a test and getting
Build failures come first 36 another pass 43
Do only what is needed to pass 38 Summary 57
viii Table of Contents
4
Adding Tests to a Project 59
Technical requirements 60 Enhancing the testing library
How to detect whether a test to support assertions 67
passes or fails 60 Should error cases be tested, too? 72
Summary 74
5
Adding More Confirm Types 75
Technical requirements 75 Adding more confirm types 87
Fixing the bool confirms 76 Confirming string literals 94
Confirming equality 76 Confirming floating point values 96
Decoupling test failures from How to write confirms 101
line numbers 82 Summary 103
6
Explore Improvements Early 105
Technical requirements 105 Exploring lambdas for tests 108
Getting line numbers without macros 106 Summary 113
7
Test Setup and Teardown 115
Technical requirements 116 teardown 145
Supporting test setup and teardown 116 Summary 150
Enhancing test setup and teardown
for multiple tests 123
Handling errors in setup and
Table of Contents ix
8
What Makes a Good Test? 151
Technical requirements 151 Only test your project 159
Making tests easy to understand 152 Test what should happen
Keeping tests focused on instead of how 159
specific scenarios 154 Summary 160
Use random behavior only in this way 157
Part 2: Using TDD to Create a Logging Library
9
Using Tests 163
Technical requirements 163 Logging and confirming
Why build a logging library? 164 the first message 172
How will TDD help build Adding timestamps 179
a logging library? 165 Constructing log messages
What would the ideal logging with streams 181
library look like? 166 Summary 185
Starting a project using TDD 169
10
The TDD Process in Depth 187
Technical requirements 188 Controlling what gets logged 235
Finding gaps in the testing 188 Enhancing filtering for
Adding log levels 190 relative matches 245
Adding default tag values 199 When is testing too much? 261
Exploring filtering options 212 How intrusive should tests be? 263
Adding new tag types 216 Where do integration or system
tests go in TDD? 264
Refactoring the tag design with TDD 221
What about other types of tests? 265
Designing tests to filter log messages 226
Summary 266
