PHP Objects, Patterns, and Practice, Third Edition

CHAPTER 18 ■ TESTING WITH PHPUNIT

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Another approach is to fake the context of the class you are testing. This involves creating objects

that pretend to be the objects that do real stuff. For example, you might pass a fake database mapper to

your test object’s constructor. Because this fake object shares a type with the real mapper class (extends

from a common abstract base or even overrides the genuine class itself), your subject is none the wiser.

You can prime the fake object with valid data. Objects that provide a sandbox of this sort for unit tests

are known as stubs. They can be useful because they allow you to focus in on the class you want to test

without inadvertently testing the entire edifice of your system at the same time. ...