Ruby Best Practices

Advanced Testing Techniques

The most basic testing techniques will get you far, but when things get complicated, you need to break out the big guns. What follows are a few tricks to try out when you run into a roadblock.

Using Mocks and Stubs

In a perfect world, all the resources that we needed would be self-contained in our application, and all interactions would take place in constant time. In our real work, life is nothing like this. We’ve got to deal with user input, database interaction, web service calls, file I/O, and countless other moving parts that live outside of our application. Testing these things can be painful.

Sure, we could set up a development database that gets blown out and reloaded every time our tests run—that’s what Rails does. We could read and write from temporary files, clearing out our leftovers after each example runs. For things like web services, we could build a fake service that acts the way we expect our live service to act and run it on a staging server. The question here is not whether it is possible to do this, but whether it is necessary.

Sometimes, you really do need to deal with real-world data. This is especially true when you want to tune and optimize performance or test resource-dependent interactions. However, in most cases, our code is mainly interested only in the behavior of the things we interact with, not what they really are. This is where either a mock or a stub could come in handy.

There are additional benefits to removing dependencies ...