This book has been written with the intention of teaching how to use Codeception in conjunction with Yii 2. By using these two great frameworks, I confirmed that testing could finally become something that anyone would appreciate doing, rather than considering it an odd and not particularly clear appendix of development.

For this reason, this first chapter tries to address several aspects that are rarely touched on but hopefully should give you the understanding and required push to learn and adopt testing, and, on a larger scale, promote testing as a way to improve development as a methodology.

In this chapter, you will see the reason for testing and why testing should be planned into a project, and not done as an afterthought.

You will also see what will happen when you start testing: the implicit and explicit benefits for the short and long term, such as a change of mentality toward testing, the ability to improve component specifications, and architectural, design, and implementation choices, as well as refactoring, redistribution, and overall quality of code.

In order to explain why testing is so important, I'll also briefly dive into the organizational part of the process where Test Driven Development (TDD) and Behavior Driven Development (BDD) will be explained in relation to modern project management techniques, such as Agile and XP in a multi-skilled, self-organized team.

You will also see how the whole team environment can be improved and re-organized to help share knowledge and speed up workflow.

This chapter has been divided into the following three sections: