It’s a persistent statement: controllers should have as little code as possible because they’re difficult, nay impossible, to test. Developers should force most of their code into the models instead, where business, validation and other logic can take place. [...] But this is not true. Controllers are no more or less testable than any other kind of code. What’s more, the fact that people believe controllers are largely untestable is an excuse for writing untestable code, not a valid design decision.
He talks briefly about where the myth might have come from (Zend Framework v1, with it's difficult to test controllers) and a note that, really, controllers are as testable as you want them to be. He give three things that could help make them easier to test:
- Using dependency injection/inversion methods
- Refactoring to use the Abstract Factory design pattern
- Using anonymous functions/closures over plain configuration settings