Working Effectively with Legacy Rails Code

Location: Pavilion 2 - 3 Level:
Average rating: ***..
(3.89, 18 ratings)

Rails has powered, a site generating tens of millions of
dollars in revenue for the past two years. It has 80 models, an equal
number of controllers, 75k lines of code…and no tests. I will talk
about how we’ve been chipping away at growing an effective, valuable
test suite since I’ve come on with Oakley.

Likewise, Rails has powered for over a year and now handles every request to the site (around 10 million unique visits a month). It has 60 controllers, 250 models, and a test suite that takes 6-8 minutes to run every time. On top of this, the Rails app still uses MediaWiki as a webservice, so it depends on an unknown number of lines of PHP which is not covered by any tests in the PHP code base. We will talk about how we are switching to Rspec and Cucumber, brought online a CI process, and how we manage code that may not be “The Rails Way”.

“Where the hell do I start?” That’s the question people ask when they
first toy with the idea of adding tests to an existing application.
We certainly can’t stop development and spend weeks just writing
tests. How do we maximize the value we get from time spent adding
tests? Writing high-level acceptance tests that step through complete
usage scenarios, are perfect for casting a big net and getting a lot
of regression coverage.

We write tests to cover existing code so that we can add new features
and fix bugs. When working on a piece of untested code, we must spend
time analyzing the possible consequences of our changes. From there,
we can write an acceptance test to cover the broad area, and then
write unit tests for various objects and methods that we touch. Then
we can test-drive the new feature or bug fix.

Maddox’s Law: 99% of untested code is untestable code. I’ll talk
about mindful refactorings that you can perform without the safety net
of tests, in order to get the code to a point where you can test it.

To keep the scope of our testing and changes small, we need to be able
to isolate dependencies in code. There are many techniques for
identifying and introduces seams into your code, which allows you to
isolate or break dependencies. I will also discuss how Ruby’s dynamic
nature enables powerful techniques that aren’t available to
programmers in other languages.

Continuous integration is extremely valuable when you’re building a
test suite. It allows you to run the slower acceptance tests
asynchrously rather than slowing down your development workflow.
Setting up CI might be a challenge in its own right, given that
testability was not built into the system. At Oakley, simply checking
out the source code and setting up an app is an ordeal, with lots of
migration scripts in different locations, external dependencies, and
hidden knowledge such as storing default values in the db at a certain
ID. I’ll talk about some of the challenges we’ve faced and how we’ve
been able to make gradual improvements.

In addition to the technical challenges, politics are another common
roadblock to introducing automated testing. How do you sell your boss
on taking some extra time to test? How can you get the other
developers in your organization on board with a testing strategy?
How do you responsibly begin testing when you don’t have much
experience with it?

Most people have a superficial understanding of how valuable testing
can be, but many people are facing too much pressure at work to feel
confident in getting started. There’s a lot of discussion about TDD
and how great it is, but in the real world we frequently have to deal
with lots of code that has not been tested at all. How can we take a
mass of untested code that runs our businesses, and start working to
the ideal of high-quality, malleable, tested code, while still meeting
the demands of high productivity in our daily work? My talk will get
people thinking and talking about that process, and give them
practical techniques for making it reality.

Photo of Pat Maddox

Pat Maddox

Goldstar Events

Pat Maddox is a freelance hacker who is particularly enamored with testing. He loves open source and is very good looking

BJ Clark

BJ has been developing websites as a freelancer and for numerous startups since 1997. He started using rails in Feb ’05 and fell in love with the framework the first time he saw hit. His skills are a unique blend of pragmatic agile development and user experience design. He currently lives in Portland, OR and works for

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Picture of Brian Hughes
Brian Hughes
05/06/2009 8:28am PDT

Really fast-paced session, but lots of good information. Pat and BJ work pretty well together. Would be great if these sessions could be 15-20 minutes longer. At the very least it could make the pacing less frenetic.

-Brian (aka. @Mac_Zealot)

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