A little more RSpec

I've been using RSpec more thoroughly recently, so I figured it's time produce a post covering some of the things I've learned.

Particularly, thanks to much forcing by Rick, I have now come to realize that RSpec involves writing two very coupled and very important documents: The spec, which describes how your code should behave, and the tests, which are attached to the spec and theoretically prove that your code does behave this way.

This was a big step in realization for me, because I had always thought of my tests as just that: tests. That is, their job was to make sure my code was behaving as I thought it should be behaving. When working with Rick the other day, though, he kept saying my spec was bad and I kept wanting to shout that I understood my tests were bad, let's just fix them.

After enough prodding, though, and some judicous using of RSpec's formatting, I came to see that he views them as separate things, and that I should too.

With RSpec, you can obviously run your tests:

luke@phage(0) $ bin/spec unit/indirector/indirector.rb
.........

Finished in 0.010605 seconds

9 examples, 0 failures
luke@phage(0) $

But you can also run them and produce a document that looks suspiciously like a spec:

luke@phage(0) $ bin/spec unit/indirector/indirector.rb  --format s

Puppet::Indirector when available to a model
- should provide a way for the model to register an indirection under a name

Puppet::Indirector when registering an indirection
- should require a name when registering a model
- should create an indirection instance to manage each indirecting model
- should not allow a model to register under multiple names
- should make the indirection available via an accessor

Puppet::Indirector when redirecting a model
- should give model the ability to lookup a model instance by letting the indirection perform the lookup
- should give model the ability to remove model instances from a terminus by letting the indirection remove the instance
- should give model the ability to search for model instances by letting the indirection find the matching instances
- should give model the ability to store a model instance by letting the indirection store the instance

Finished in 0.014107 seconds

9 examples, 0 failures
luke@phage(0) $

Note that it's still running the tests here (as shown by the lack of failures at the bottom), it's just producing output differently.

I was surprised to find Rick wanting to read this output again and again, completely ignoring any associated test code. It finally hit me, of course, that if we aren't doing a good job of describing the expected behaviour, then how can we do a good job of testing it?

When we first started working through some code recently, he kept niggling about some code that wasn't in the spec, which kinda miffed me because it was clearly being tested. When I finally realized what he meant about the difference between the spec and the tests, no matter how tightly coupled they are, I realized why it mattered so much to him: There was behaviour in my code that I essentially hadn't documented, even if I was confident I was testing that it was working.

Certainly an interesting realization.

Sun, 23 Sep 2007 | Tags: ruby, rspec, puppet, development, programming, testing, bdd