Posts Tagged ‘tdd’

being too rapid on the things that matter

Thursday, May 7th, 2009

it took me a while to come up with the title for this post. and it’s and Opinion Piece, not Techincal … so you’ll see why …

i’m working for a new company now, and they’re rocking it for RoR apps on the iPhone. sounds like a good place to be. one of the many reasons why this position works for me is because these guys are all about GTD and getting it out there. lean ‘n’ mean

whereas i’ve become very used to a holistic detail-orented, wisened test-backed process. great for Enterprise, but not so much for the reckless streets of Startup 3.0 . so i’m in a learning process. i’ve turned around some good stuff quickly, and it’s very satisfying

but i’ve screwed the pooch twice since i’ve been there. it’s totally a judgement call thing — i’m shooting too fast from the hip, and don’t feel like i really grasp the balance here …

first project i worked on was related to account management. they wanted a quick turn-around, i gave it a shot, had the whole thing backed with solid testing, and ready for on-time deployment with a smile. and in trying to keep track of all the new system permutations — i’d been there 2 weeks or so — i forgot one basic thing, and forgot to test for another. a nice little Perfect Storm. one emergency 1am database rollback later, we had a load of pissed customers and a helluva lot of explaining to do

so, then this past week, i went in to fix a minor rounding issue bug. those can be touchy. the right way to do it is with BigDecimal. yep, i’ve done that in Java too with BigDecimal. overall, it’s somewhat ponderous, detail-oriented, and can easily be polluted with Floats and the like. so i’d taken a shortcut, realizing that the low-level C impl was doing String conversion without the rounding issue. so i took the low-hanging fruit:

total.to_s.to_i

awesome !!1!. well, that is until you get into the 100-of-trillions area, otherwise shown as 1.0e+14. guess what happens when you parse that into a Fixnum? no database rollback this time, but Da Boss had to spend days sorting out the visceral impact of ridiculous sums of bogus exploit money pouring into our RPG

security, privacy and account management. payment calculations. not the sort of things to take shortcuts on. yet, if you’re embracing a culture that wants it done quickly and with minimum impact, it’s a risk you might be willing to take. it’s not like i didn’t have test scripts … i just forgot to head into scientific notation territory. just like i forgot to check for the implication of null password acceptance ( long story there, special account cases, etc. )

i’m putting these things up here for my fellow developers to laugh at.   “I mean, c’mon. All that’s totally obvious stuff.”   “I’d never miss that, that’s sophmore shit.”   good, get it out of your system, laughing boy

but believe me, when you’re on the other end of it, and had been in the middle of it and all full of all the other things that you needed to keep track of at that time, heh, well, that’s when you’ll really need to keep yerself laughing :)

Twitter4R shifts RSpec onto my Front Burner

Thursday, February 5th, 2009

As usual, my day did not pan out as expected. But, also as usual, I learned a lot!

Coming Up To Speed on Rspec

So, learning rspec has been on my list for a while. I finally got around to it. Nice framework. I am familiar with EasyMock, and am aware of JMock. I never had an opportunity to get into Mockito, but I’d give it a glance next time I put on my Java hat.

There is some decent documentation on it out there. I found these links particularly helpful:

During my ramping-up, I took the usual meta-approach of creating a test suite — and yaaay, that’s what rspec is meant for! — which I then used to test out its own range of capabilities. The Modules in the rdoc which I’ve found to provide the most value are:

  • Spec::Expectations::ObjectExpectations for conditionals (eg. should & should_not)
  • Spec::Matchers for expectations (eg. equal(value), be_a(class), respond_to(method_sym), raise_error)
  • Spec::Mocks::Methods for mock method definition (eg. should_receive(method_sym))
  • Spec::Mocks::MessageExpectation for mock behaviour (eg. with(*args), once, exactly(n).times, any_number_of_times)
  • Spec::Mocks::ArgumentConstraints for mock arguments (eg. an_instance_of(class), anything)
  • Spec::Mocks::BaseExpectation for mock responses (eg. and_return(value), and_yield(&block))

I won’t got into the deep details, but here are some examples of conditionals and expectations that I paraphrased into my meta-test:

And here’s a little bit of silly mocking:

These are just ways I thought of to exercise the width and breadth of the library. Very nice. I hope that these are useful examples for people new to this gem.

I recommend the other references from above for filling in the missing details. Once you have a context / specify or a describe / it specification set up, you’ll be good to go. There’s much more to the library — Stories, for instance — but that’s for another day.

An Informative Walk through Twitter4R

No, I didn’t really want to spend time learning rspec — I mean heck, I’m busy — but I had a personal need to expand the Twitter4R gem. Specifically, I wanted to add on some Twitter search features, and I was very impressed with how this library has been built. Contribution-wise, the final step that Susan Potter recommends is to craft up some rspec tests.

Of course, mock testing is only as good as the framework you’re built upon. The assumption is that Net::HTTP is going to do it’s job, so mock it up and you can even test your Twitter features offline. When I built Bitly4R (given that name, my thinking has clearly been influenced), I did everything as full-on functional tests. It was easy; bit.ly has both shorten and expand commands, so I could reverse-test real values without having any fixed expectations.

However, Twitter is live and user-generated, so who knows what you’ll find. Mocking covers that for you. And of course not having to hit the service itself shortest testing time dramatically.

Here’s one of my tests, again foreshortened:

Plus a little mocking of Net::HTTPResponse:

Nothing like having some good inspiration to get you thinking about maintainability. I’m a not a strong adherent to any of the TDD or BDD denominations, but testability itself is close to my heart. Just ask the folks who’ll be looking at the micro-assertion Module that I wrote for my Facebook Puzzle submissions (which work locally under test conditions but fail miserably once thrown over their wall). Then again, I won’t need to write that (and test that) from scratch again.

So, back to talking glowingly about the Twitter4R architecture. Yes, I used that word. Yet regardless of that term’s heavyweightedness, it’s simply the result of carefully thinking out the formalization of a complex design. And once a non-author delves into extending an existing implementation, that impl’s demeanor becomes readily clear :)

Some of the interesting things I saw:

  • An inner bless-ish strategy, to inject the Twitter::Client into instanciated result classes. I’ve seen blessing as an OO-Perl-ism, for self-ication, and that metaphor carries over very nicely to this context.
  • Generous use of blocks / lambdas / closures in methods, for contextual iteration (eg. iterate through each Twitter::Message in a timeline response). Unnecessary, but an excellent convenience for a language that offers that optional capability in a very disposable fashion (from the caller’s perspective).
  • Retroactive sub-object population after construction. Twitter4R relies upon the json gem, which deals primarily in Hashes. Post-injection, the library itereates through Arrays of Hashes and transforms them into suitable Twiltter::User containers, etc. A great place to put such logic in the construction chain, and it doesn’t take long to get really tired of Hash hierarchies.

Good stuff, and learning with in a Ruby-centric mindset was invaluable for me. We all have to start somewhere, eh.

The Acute Long-Term Pain of Staticness

There was one issue that I ran into; static configuration. During my years of using the Spring Framework, my IOC-addled brain started thinking of everything in terms of instances — Factory Beans, POJOs, Observers & Listeners, Chain-of-Responsibility wrappers. Static configuration is a common metaphor, and in this case, there’s a static Twitter::Config instance. Convenient and centralized. Makes perfect sense.

I mean, the fact that it was a configurable library at all was awesome. I was able to easily set up a Twitter::Client to reference search.twitter.com. However, of course as soon as I did that, I whacked the ability for clients to talk to twitter.com in the process. Oops!

On GPs, I refused to modify the original code. And I wanted to make sure that my superficial tweaks to the library would be thread-safe — temporarily swaping out the global Twitter::Config in mid-operation would be an issue. Using Mutex.synchronize seemed like the perfect choice. After finding that the same thread can’t lock a Mutex instance twice — grr!, that’s a great trick if you can work it — I overrode the one method that cared the most about @@config:

It works like a charm. Please, everyone just line up to tell me how I could have done it better. And I don’t mean quicker or cheaper, I mean better. Believe me, I would not have sunk the time into this end-around approach, if not for the fact that:

  1. I don’t want to maintain a local gem code modification (even though my impl is closely coupled to the gem impl already)
  2. I intend to follow that practice, so every opportunity to pull and end-around is a Valuable Learning Experience.

So, now my local Twitter4R has search capability gracefully latched onto it (and implemented much in the flavor of the library itself). I have a mass of rspec examples to work off in the future.

Now, I haven’t spent a great amount of time testing the thread-safeness — no one in their right mind wants to do that — but my sundry Twitter::Client instances play nicely together in between searches and normal status operations.

And I had something useful to blog about!