Testing objects with dependencies in PHPUnit

Question

For objects which compose another object as part of their implementation, what\'s the best way to write the unit test so only the principle object gets tested? Trivial example:

Answer 1

As you seem to be aware already, Concrete Class Dependencies makes testing hard (or outright impossible). You need to decouple that dependency. A simple change, that doesn't break the existing API, is to default to the current behaviour, but provide a hook to override it. There are a number of ways that this could be implemented.

Some languages have tools that can inject mock classes into code, but I don't know of anything like this for PHP. In most cases, you would probably be better off refactoring your code anyway.