Unit Testing Principles, Practices, and Patterns

Chapter 8. Why integration testing?

This chapter covers

• Understanding the role of integration testing
• Diving deeper into the Test Pyramid concept
• Writing valuable integration tests

You can never be sure your system works as a whole if you rely on unit tests exclusively. Unit tests are great at verifying business logic, but it’s not enough to check that logic in a vacuum. You have to validate how different parts of it integrate with each other and external systems: the database, the message bus, and so on.

In this chapter, you’ll learn the role of integration tests: when you should apply them and when it’s better to rely on plain old unit tests or even other techniques such as the Fail Fast principle. You will see which out-of-process dependencies ...