The Devver Blog

A Boulder startup improving the way developers work.

Archive for the ‘Hacking’ Category

Speeding up multi-browser Selenium Testing using concurrency

I haven’t used Selenium for awhile, so I took some time to dig into the options to get some mainline tests running against Caliper in multiple browsers. I wanted to be able to test a variety of browsers against our staging server before pushing new releases. Eventually this could be integrated into Continuous Integration (CI) or Continuous Deployment (CD).

The state of Selenium testing for Rails is currently in flux:

So there are multiple gems / frameworks:

I decided to investigate several options to determine which is the best approach for our tests.


I originally wrote a couple example tests using the selenium-on-rails plugin. This allows you to browse to your local development web server at ‘/selenium’ and run tests in the browser using the Selenium test runner. It is simple and the most basic Selenium mode, but it obviously has limitations. It wasn’t easy to run many different browsers using this plugin, or use with Selenium-RC, and the plugin was fairly dated. This lead me to try simplest next thing, selenium-client

open '/'
assert_title 'Hosted Ruby/Rails metrics - Caliper'
verify_text_present 'Recently Generated Metrics'

click_and_wait "css=#projects a:contains('Projects')"
verify_text_present 'Browse Projects'

click_and_wait "css=#add-project a:contains('Add Project')"
verify_text_present 'Add Project'

type 'repo','git://'
click_and_wait "css=#submit-project"
verify_text_present 'sinatra/sinatra'
wait_for_element_present "css=#hotspots-summary"
verify_text_present 'View full Hot Spots report'

view this gist


I quickly converted my selenium-on-rails tests to selenium-client tests, with some small modifications. To run tests using selenium-client, you need to run a selenium-RC server. I setup Sauce RC on my machine and was ready to go. I configured the tests to run locally on a single browser (Firefox). Once that was working I wanted to run the same tests in multiple browsers. I found that it was easy to dynamically create a test for each browser type and run them using selenium-RC, but that it was increadly slow, since tests run one after another and not concurrently. Also, you need to install each browser (plus multiple versions) on your machine. This led me to use Sauce Labs’ OnDemand. '/'
assert_equal 'Hosted Ruby/Rails metrics - Caliper', browser.title
assert browser.text?('Recently Generated Metrics') "css=#projects a:contains('Projects')", :wait_for => :page
assert browser.text?('Browse Projects') "css=#add-project a:contains('Add Project')", :wait_for => :page
assert browser.text?('Add Project')

browser.type 'repo','git://' "css=#submit-project", :wait_for => :page
assert browser.text?('sinatra/sinatra')
browser.wait_for_element "css=#hotspots-summary"
assert browser.text?('View full Hot Spots report')

view this gist

Using Selenium-RC and Sauce Labs Concurrently

Running on all the browsers Sauce Labs offers (12) took 910 seconds. Which is cool, but way too slow, and since I am just running the same tests over in different browsers, I decided that it should be done concurrently. If you are running your own Selenium-RC server this will slow down a lot as your machine has to start and run all of the various browsers, so this approach isn’t recommended on your own Selenium-RC setup, unless you configure Selenium-Grid. If you are using  Sauce Labs, the tests run concurrently with no slow down. After switching to concurrently running my Selenium tests, run time went down to 70 seconds.

My main goal was to make it easy to write pretty standard tests a single time, but be able to change the number of browsers I ran them on and the server I targeted. One approach that has been offered explains how to setup Cucumber to run Selenium tests against multiple browsers. This basically runs the rake task over and over for each browser environment.

Althought this works, I also wanted to run all my tests concurrently. One option would be to concurrently run all of the Rake tasks and join the results. Joining the results is difficult to do cleanly or you end up outputting the full rake test output once per browser (ugly when running 12 times). I took a slightly different approach which just wraps any Selenium-based test in a run_in_browsers block. Depending on the options set, the code can run a single browser against your locally hosted application, or many browsers against a staging or production server. Then simply create a separate Rake task for each of the configurations you expect to use (against local selenium-RC and Sauce Labs on demand).

I am pretty happy with the solution I have for now. It is simple and fast and gives another layer of assurances that Caliper is running as expected. Adding additional tests is simple, as is integrating the solution into our CI stack. There are likely many ways to solve the concurrent selenium testing problem, but I was able to go from no Selenium tests to a fast multi-browser solution in about a day, which works for me. There are downsides to the approach, the error output isn’t exactly the same when run concurrently, but it is pretty close.  As opposed to seeing multiple errors for each test, you get a single error per test which includes the details about what browsers the error occurred on.

In the future I would recommend closely watching Webrat and Capybara which I would likely use to drive the Selenium tests. I think the eventual merge will lead to the best solution in terms of flexibility. At the moment Capybara doesn’t support selenium-RC, and the tests I originally wrote didn’t convert to the Webrat API as easily as directly to selenium-client (although setting up Webrat to use Selenium looks pretty simple). The example code given could likely be adapted easily to work with existing Webrat tests.

namespace :test do
  namespace :selenium do

    desc "selenium against staging server"
    task :staging do
      exec "bash -c 'SELENIUM_BROWSERS=all SELENIUM_URL=  ruby test/acceptance/walkthrough.rb'"

    desc "selenium against local server"
    task :local do
      exec "bash -c 'SELENIUM_BROWSERS=one SELENIUM_RC_URL=localhost SELENIUM_URL=http://localhost:3000/ ruby test/acceptance/walkthrough.rb'"

view this gist

require "rubygems"
require "test/unit"
gem "selenium-client", ">=1.2.16"
require "selenium/client"
require 'threadify'

class ExampleTest  1
      errors = []
      browsers.threadify(browsers.length) do |browser_spec|
          run_browser(browser_spec, block)
        rescue => error
          type = browser_spec.match(/browser\": \"(.*)\", /)[1]
          version = browser_spec.match(/browser-version\": \"(.*)\",/)[1]
          errors < type, :version => version, :error => error}
      message = ""
      errors.each_with_index do |error, index|
        message +="\t[#{index+1}]: #{error[:error].message} occurred in #{error[:browser]}, version #{error[:version]}\n"
      assert_equal 0, errors.length, "Expected zero failures or errors, but got #{errors.length}\n #{message}"
      run_browser(browsers[0], block)

  def run_browser(browser_spec, block)
    browser =
                                           :host => selenium_rc_url,
                                           :port => 4444,
                                           :browser => browser_spec,
                                           :url => test_url,
                                           :timeout_in_second => 120)

  def test_basic_walkthrough
    run_in_all_browsers do |browser| '/'
      assert_equal 'Hosted Ruby/Rails metrics - Caliper', browser.title
      assert browser.text?('Recently Generated Metrics') "css=#projects a:contains('Projects')", :wait_for => :page
      assert browser.text?('Browse Projects') "css=#add-project a:contains('Add Project')", :wait_for => :page
      assert browser.text?('Add Project')

      browser.type 'repo','git://' "css=#submit-project", :wait_for => :page
      assert browser.text?('sinatra/sinatra')
      browser.wait_for_element "css=#hotspots-summary"
      assert browser.text?('View full Hot Spots report')

  def test_generate_new_metrics
    run_in_all_browsers do |browser| '/' "css=#add-project a:contains('Add Project')", :wait_for => :page
      assert browser.text?('Add Project')

      browser.type 'repo','git://' "css=#submit-project", :wait_for => :page
      assert browser.text?('sinatra/sinatra') "css=#fetch"
      assert browser.text?('sinatra/sinatra')


view this gist

Written by DanM

April 8, 2010 at 10:07 am

Playing with Processing, Making Snow

What is Processing?

“Processing is an open source programming language and environment for people who want to program images, animation, and interactions.”

I wanted to play around with doing some visual programming and had played with Processing in the past. I recently had been reading about Ruby-Processing and wanted to give it a shot. First, I went to look for some Ruby-Processing tutorials, and I had recently heard about the presentation by Jeff Casimir about the ‘Art of Code‘ (slides and code), using Ruby-Processing. I went through those examples and decided I wanted to modify it to display snowflakes in the spirit of winter. After a bit of searching I found a project that generated a Penrose snow flake using Ruby-Processing. I figured I could modify the programs to get a nice snow flake screen saver type app. The result is my app Processing-Snow, and is shown in the screen shot below.


Playing around with Ruby-Processing is a lot of fun, I highly recommend spending a couple hours to make a tiny app. I built my Snow app in about an hour and a half. Then I spent a bit of time using Caliper to improve the metrics. For such a small project there wasn’t a lot to improve, but it still helped me to do some refactoring. To get an idea of the code you can view Processing-Snow’s Metrics.

Feel free to fork Processing-Snow on GitHub and read about how to run it with in the projectss README.

Written by DanM

December 23, 2009 at 8:16 pm

Posted in Hacking, Misc, Ruby

Making Rack::Reloader work with Sinatra

According to the Sinatra FAQ, source reloading was taken out of Sinatra in version 0.9.2 due to “excess complexity” (in my opinion, that’s a great idea, because it’s not a feature that needs to be in minimal a web framework like Sinatra). Also, according to the FAQ, Rack::Reloader (included in Rack) can be added to a Sinatra application to do source reloading, so I decided to try it out.

Setting up Rack::Reloader is easy:

require 'sinatra'
require 'rack'

configure :development do
  use Rack::Reloader

get "/hello" do
$ ruby hello.rb
== Sinatra/0.9.4 has taken the stage on 4567 for development with backup from Thin
>> Thin web server (v1.2.4 codename Flaming Astroboy)
>> Maximum connections set to 1024
>> Listening on, CTRL+C to stop
[on another terminal]
$ curl http://localhost:4567/hello

If you add another route, you can access it without restarting Sinatra:

get "/goodbye" do
$ curl http://localhost:4567/goodbye

But what happens when you change the contents of a route?

get "/hello" do
$ curl http://localhost:4567/hello

You still get the old value! What is going on here?

Rack::Reloader simply looks at all files that have been required and, if they have changed on disk, re-requires them. So each Sinatra route is re-evaluated when a reload happens.

However, identical Sinatra routes do NOT override each other. Rather, the first route that is evaluated is used (more precisely, all routes appended to a list and the first matching one is used, so additional identical routes are never run).

We can see this with a simple example:

require 'sinatra'

get "/foo" do

get "/foo" do
$ curl http://localhost:4567/foo
foo   # The result is 'foo', not 'bar'

Clearly, Rack::Reloader is not very useful if you can’t change the contents of any route. The solution is to throw away the old routes when the file is reloaded using


, like so:

configure :development do
  use Rack::Reloader
$ curl http://localhost:4567/hello


A word of caution: you MUST call


very early in your file – before you add any middleware, do any other configuration, or add any routes.

This method has worked well enough for our Sinatra application. However, code reloading is always tricky and is bound to occasionally produce some weird results. If you want to significantly reduce the chances for strange bugs (at the expense of code loading time), try Shotgun or Rerun. Happy reloading!

Written by Ben

December 21, 2009 at 3:20 pm

Improving Code using Metric_fu

Often, when people see code metrics they think, “that is interesting, I don’t know what to do with it.” I think metrics are great, but when you can really use them to improve your project’s code, that makes them even more valuable. metric_fu provides a bunch of great metric information, which can be very useful. But if you don’t know what parts of it are actionable it’s merely interesting instead of useful.

One thing when looking at code metrics to keep in mind is that a single metric may not be as interesting. If you look at a metric trends over time it might help give you more meaningful information. Showing this trending information is one of our goals with Caliper. Metrics can be your friend watching over the project and like having a second set of eyes on how the code is progressing, alerting you to problem areas before they get out of control. Working with code over time, it can be hard to keep everything in your head (I know I can’t). As the size of the code base increases it can be difficult to keep track of all the places where duplication or complexity is building up in the code. Addressing the problem areas as they are revealed by code metrics can keep them from getting out of hand, making future additions to the code easier.

I want to show how metrics can drive changes and improve the code base by working on a real project. I figured there was no better place to look than pointing metric_fu at our own website source and fixing up some of the most notable problem areas. We have had our backend code under metric_fu for awhile, but hadn’t been following the metrics on our Merb code. This, along with some spiked features that ended up turning into Caliper, led to some areas getting a little out of control.

Flay Score before cleanup

When going through metric_fu the first thing I wanted to start to work on was making the code a bit more DRY. The team and I were starting to notice a bit more duplication in the code than we liked. I brought up the Flay results for code duplication and found that four databases models shared some of the same methods.

Flay highlighted the duplication. Since we are planning on making some changes to how we handle timestamps soon, it seemed like a good place to start cleaning up. Below are the methods that existed in all four models. A third method ‘update_time’ existed in two of the four models.

 def self.pad_num(number, max_digits = 15)
    "%%0%di" % max_digits % number.to_i

  def get_time

Nearly all of our DB tables store time in a way that can be sorted with SimpleDB queries. We wanted to change our time to be stored as UTC in the ISO 8601 format. Before changing to the ISO format, it was easy to pull these methods into a helper module and include it in all the database models.

module TimeHelper

  module ClassMethods
    def pad_num(number, max_digits = 15)
      "%%0%di" % max_digits % number.to_i

  def get_time

  def update_time
    self.time = self.class.pad_num(


Besides reducing the duplication across the DB models, it also made it much easier to include another time method update_time, which was in two of the DB models. This consolidated all the DB time logic into one file, so changing the time format to UTC ISO 8601 will be a snap. While this is a trivial example of a obvious refactoring it is easy to see how helper methods can often end up duplicated across classes. Flay can come in really handy at pointing out duplication that over time that can occur.

Flog gives a score showing how complex the measured code is. The higher the score the greater the complexity. The more complex code is the harder it is to read and it likely contains higher defect density. After removing some duplication from the DB models I found our worst database model based on Flog scores was our MetricsData model. It included an incredibly bad high flog score of 149 for a single method.

File Total score Methods Average score Highest score
/lib/sdb/metrics_data.rb 327 12 27 149

The method in question was extract_data_from_yaml, and after a little refactoring it was easy to make extract_data_from_yaml drop from a score of 149 to a series of smaller methods with the largest score being extract_flog_data! (33.6). The method was doing too much work and was frequently being changed. The method was extracting the data from 6 different metric tools and creating summary of the data.

The method went from a sprawling 42 lines of code to a cleaner and smaller method of 10 lines and a collection of helper methods that look something like the below code:

  def self.extract_data_from_yaml(yml_metrics_data)
    metrics_data = {|hash, key| hash[key] = {}}
    extract_flog_data!(metrics_data, yml_metrics_data)
    extract_flay_data!(metrics_data, yml_metrics_data)
    extract_reek_data!(metrics_data, yml_metrics_data)
    extract_roodi_data!(metrics_data, yml_metrics_data)
    extract_saikuro_data!(metrics_data, yml_metrics_data)
    extract_churn_data!(metrics_data, yml_metrics_data)

  def self.extract_flog_data!(metrics_data, yml_metrics_data)
    metrics_data[:flog][:description] = 'measures code complexity'
    metrics_data[:flog]["average method score"] = Devver::Maybe(yml_metrics_data)[:flog][:average].value(N_A)
    metrics_data[:flog]["total score"]   = Devver::Maybe(yml_metrics_data)[:flog][:total].value(N_A)
    metrics_data[:flog]["worst file"] = Devver::Maybe(yml_metrics_data)[:flog][:pages].first[:path].fmap {|x|}.value(N_A)

Churn gives you an idea of files that might be in need of a refactoring. Often if a file is changing a lot it means that the code is doing too much, and would be more stable and reliable if broken up into smaller components. Looking through our churn results, it looks like we might need another layout to accommodate some of the different styles on the site. Another thing that jumps out is that both the TestStats and Caliper controller have fairly high churn. The Caliper controller has been growing fairly large as it has been doing double duty for user facing features and admin features, which should be split up. TestStats is admin controller code that also has been growing in size and should be split up into more isolated cases.

churn results

Churn gave me an idea of where might be worth focusing my effort. Diving in to the other metrics made it clear that the Caliper controller needed some attention.

The Flog, Reek, and Roodi Scores for Caliper Controller:

File Total score Methods Average score Highest score
/app/controllers/caliper.rb 214 14 15 42

reek before cleanup

Roodi Report
app/controllers/caliper.rb:34 - Method name "index" has a cyclomatic complexity is 14.  It should be 8 or less.
app/controllers/caliper.rb:38 - Rescue block should not be empty.
app/controllers/caliper.rb:51 - Rescue block should not be empty.
app/controllers/caliper.rb:77 - Rescue block should not be empty.
app/controllers/caliper.rb:113 - Rescue block should not be empty.
app/controllers/caliper.rb:149 - Rescue block should not be empty.
app/controllers/caliper.rb:34 - Method name "index" has 36 lines.  It should have 20 or less.

Found 7 errors.

Roodi and Reek both tell you about design and readability problems in your code. The screenshot of our Reek ‘code smells’ in the Caliper controller should show how it had gotten out of hand. The code smells filled an entire browser page! Roodi similarly had many complaints about the Caliper controller. Flog was also showing the file was getting a bit more complex than it should be. After picking off some of the worst Roodi and Reek complaints and splitting up methods with high Flog scores, the code had become easily readable and understandable at a glance. In fact I nearly cut the Reek complaints in half for the controller.

Reek after cleanup

Refactoring one controller, which had been quickly hacked together and growing out of control, brought it from a dizzying 203 LOC to 138 LOC. The metrics drove me to refactor long methods (52 LOC => 3 methods the largest being 23 LOC), rename unclear variable names (s => stat, p => project), move some helpers methods out of the controller into the helper class where they belong. Yes, all these refactorings and good code designs can be done without metrics, but it can be easy to overlook bad code smells when they start small, metrics can give you an early warning that a section of code is becoming unmanageable and likely prone to higher defect rates. The smaller file was a huge improvement in terms of cyclomatic complexity, LOC, code duplication, and more importantly, readability.

Obviously I think code metrics are cool, and that your projects can be improved by paying attention to them as part of the development lifecycle. I wrote about metric_fu so that anyone can try these metrics out on their projects. I think metric_fu is awesome, and my interest in Ruby tools is part of what drove us to build Caliper, which is really the easiest way try out metrics for your project. Currently, you can think of it as hosted metric_fu, but we are hoping to go even further and make the metrics clearly actionable to users.

In the end, yep, this is a bit of a plug for a product I helped build, but it is really because I think code metrics can be a great tool to help anyone with their development. So submit your repo in and give Caliper hosted Ruby metrics a shot. We are trying to make metrics more actionable and useful for all Ruby developers out, so we would love to here from you with any ideas about how to improve Caliper, please contact us.

Written by DanM

October 27, 2009 at 10:30 pm

Lone Star Ruby Conf 2009 Wrapup Review

I recently went to the Lone Star Ruby Conference (LSRC), in Austin TX. It was great to be able to put faces to many people I had interacted with in the Ruby community via blogs and twitter. I also got to meet Matz and briefly talk with him, which was cool. Meeting someone who created a language which is such a large part of your day to day life is just an interesting experience. I enjoyed LSRC, and just wanted to give a quick summary of some of the talks that I saw and enjoyed. This is by no means full coverage of the event, but hopefully sharing my experience with others is worth something. If you are interested in seeing any of the talks keep an eye out for Confreaks, they taped the event and many of the talks should be coming online soon.

Dave Thomas
Dave was the first speaker for LSRC, and it was a great way to kick off the event. Dave gave a talk about Ruby not being perfect and that is why he likes it. I have heard Dave speak before, and I always enjoy his talks. It isn’t like you learn anything specific about Ruby development, but you learn about the Ruby community. Actually, Dave would say we are a collection of Ruby communities, and that having a collection of communities is a good thing. It was also interesting to hear Dave speak about the entire Zed, “Rails is a Ghetto” incident. Sometimes when you are angrily ranting around online, it is easy to forget that there are real people attached to things. Feelings can get hurt, and while Dave agrees there is some valid points in the post, I think it shows that it probably isn’t a good way to go about fixing them. Dave really loves Ruby and the weird things you can do with the language and it shows.

Glenn Vanderburg, Programming Intuition
Glenn talked about phyical emotions tied to code, such as a sense of touch or smell. The talk generally just evoked memories of Paul Graham’s “Hackers and Painters” in my head, in fact Glenn talked about PG during his talk. The best programmers talk about code as if they can see it. The talk explored ways to feel the code and react to it. It tried to promote the idea that it is OK to just have a gut reaction that some code is a bad way to do things, because we should sense the code. Glenn also played a video showing Bobby McFerrin teaching the audience the Pentatonic scale, which I really enjoyed.

James Edward Gray II, Module Magic
James visited Japan recently and went to a Ruby conference, and he really enjoyed it. About half his talk was why Japan is awesome… He then found little ways to tie this back into his talk about Ruby and Modules. It covered some interesting topics like load order that many people just don’t know enough about, but use every day. Examples of the differences between include and extend. Modules are terrific at limiting scope, limit the scope of scary magic and keep it hidden away. I enjoyed talking with James a good amount through out the conference. I had never met him before LSRC, but I used to practice Ruby working on Ruby Quiz which he ran for a long time.

James has his slides are up, Module Magic

Fernand Galiana, R-House
Fernand gave a really cool and demo heavy talk about home automation. He has a web front end that lets him interact with all his technology. His house tweets most of the events that it runs. The web interface has a iPhone front in, so he can, on the go, change the temperature or turn off lights. I have always been a real home automation geek. When I was growing up, my dad loved playing with an X-10 system that we had in the house. I am really interested in playing with some of this stuff when I have my own place, mostly looking at ways I could use it to cut waste on my energy usage.

Mike Subelsky, Ruby for Startups: Battle Scars and Lessons Learned
* You Ain’t Gonna Need It (YAGNI), don’t worry about being super scaling at the beginning…
* Early days focus on learning more data about what your building and what your customers want concentrate on the first 80% solution.
* Don’t over build, over design, or over engineer.
* Eventually plan to move everything out of your web request, build it so that it will be easy to do in the future, but it isn’t worth doing at first. (delayed job, EM, etc)
* Make careful use of concurrency, prefer processes communicating via messages (SQS etc…) If you are doing threading in your software EM is your friend.
* Avoid touching your RDBMS when you are storing not critical data:
– Storing large text blogs in S3, message across SQS, tons of logging SDB
* Don’t test all the time at the beginning, it gets in the way of exploration… Things that is mission critical maybe should be BDD as it will be the most stable and least likely to change part of your code

Mike posted his slides on his blog, Ruby for Startups.

Jeremy Hinegardner, Playing nice with others. — Tools for mixed language environments

Jeremy wanted to show how easy it is to use some code to make it easy to work with a system that uses multiple languages. He brought up that most projects in the room utilize more than one language. That it will be more common as systems grow in complexity. He looked at a lot of queues, key value stores, and cache-like layers that can be talked to by a variety of language. He then showed some code that would quickly demonstrate how easy it was to work with some of these tools. Extra points because he talked about Beanstalkd, which I personally think is really cool. I think nearly everyone is starting to look at work queues, messaging systems, and non standard databases for their project and this was a good overview of options that are out there.

Yukihiro Matsumoto (Matz), Keynote and Q&A
Matz gave a talk about why we, as a community, love Ruby. In this talk there weren’t really any takeaways that were specifically about Ruby code but more about the community and why Ruby is fun. He spent a good amount of time talking about Quality Without A Name, QWAN. More interesting than the talk was the Q&A session. I thought the most interesting question was why Ruby isn’t on Git yet. He said the teams doesn’t have time to convert all the tools they use from SVN to git. He also mentioned that the git project tracking SVN is very close to the SVN master and is a good way to work on the Ruby code.

Evan Light, TDD: More than just “testing”
Evan first covered that the tools we as a community keep getting excited about aren’t really what matters. What matters is TDD technique. After discussing why tools aren’t as important for awhile, Evan began live coding with the audience. Something I thought was pretty impressive as it would be difficult to do. It made for a weird pair programming exercise with the entire audience trying to drive. Which sometimes worked well and sometimes lead to conflicting ideas / discussion (which made for interesting debate). It was over all a really interesting session, but it is hard to pull out specific tidbits of wisdom from the talk.

Jake Scruggs, What’s the Right Level of Testing?
I have known of Jake for awhile from his work on the excellent Metric Fu gem. Jake explored what the right level of testing for a project is, from his experience on his last nine projects over the years. He explored what worked, what didn’t and what sometimes works but only depending on the people and the project. I think it comes to this conclusion: what works for one project won’t work for all projects. Having some testing and getting the team on a similar testing goal will make things much better. He also stressed the importance of metrics along with testing (really? From the metric-fu guy? Haha). If testing is old and broken, causing team backlash, low morale, and gridlock, it might be better to lessen the testing burden or throw away difficult to maintain tests. Getting rid of them and getting them out of the way, might be worth more than the value the tests were providing. In general he isn’t big into view testing, he likes to avoid slow testing. He likes to have a small ‘smoke screen’ of integration tests, to help verify the system is all working together. In the end, what is the right level of testing for a project? The answer: what level of assurance does the given project really need? In a start-up you probably don’t need a huge level of assurance, speed matters and market feedback matter more. If your building parts for a rocket or medical devices it is entirely different.

I enjoyed this talk quite a bit, and it inspired me to fix our broken metric_fu setup and start tracking on projects metrics again. Jake also wrote a good roundup of LSRC

Corey Donohoe @atmos, think simple
Corey gave interesting quick little thoughts and ideas about how to stay productive, happy, learn more, do more, fail less, and keep things simple and interesting… Honestly with something like 120+ slides, I can’t even begin to summarize this talk. I checked around and couldn’t find his slides online, but they couldn’t really do the talk justice anyways. Keep your eyes peeled for the video as it was a fun talk, which I enjoyed. Until then here is a post he made about heading to LSRC.

Joseph Wilk, Outside-in development with Cucumber
Cucumber is something I keep hearing and reading about, but haven’t really gotten a chance to play with it myself. Joseph’s talk was a good split between a quick intro to Cucumber, and diving in deeper to actually show testing examples and how it worked. From the talk it sounded to me like Cucumber was mostly a DSL to talk between the customer and the developer/tester. I don’t know if that is how others would describe it. I thought Cucumber was an odd mix of English and and Ruby, but it helps effectively tell a story. Since returning form LSRC, I have started working on my first Cucumber test.

Yehuda Katz, Bundler
This was just a lightening talk about Bundler, which I had read about briefly online. Seeing the work that was done for this blew me away. I can honestly say I hope this takes over the Ruby world. We have been dealing with so many problems related to gems at Devver, and if Bundler becomes a standard, it would make the Ruby community a better place. I am really excited about this so go check out the Bundler project now.

Rich Kilmer, Encoding Domains
The final keynote of the event was about encoding domains. I didn’t really know what to expect going into this talk, but I was happily surprised. Rich talked about really encapsulating a domain in Ruby and then being able to make the entire programming logic much simpler. He gave compelling examples of working with knowledge workers in the field and just writing code with them to express their domain of knowledge in Ruby code. Live coding with the domain with experts he jokingly called “syntax driven development” – you write code with them until it doesn’t raise syntax errors. Rich spoke energetically and keep a tiring audience paying attention to his stories about projects he has worked on through out the years. Just hearing about people who have created successful projects who have been working with Ruby in the industry this long is interesting. I thought it had great little pieces of knowledge that were shared during the talk, but again this was a talk where it was to hard to pull out tiny bits of information, so I recommend looking for the video when it is released.

Final Thoughts
LSRC was a good time besides hearing all the speakers. In fact like most conferences some of the best knowledge sharing happened during breaks, at dinner, and in the evenings. It also gave me a chance to get to know some of the community better than just faceless Twitter avatars. It was fun to talk with Ruby people about things that had nothing to do with Ruby. I also am interested in possibly living in Austin at some point in my life so it was great to check it out a bit. Friday night after the conference I went out with a large group of Rubyists to Ruby’s BBQ, which was delicious. We ate outside with good food, good conversation, and live music playing next door. As we were leaving someone pointed out that the guitarist playing next door was Jimmy Vaughn, brother of the even more famous Stevie Ray Vaughan. We went over to listen to the show and have a beer, which quickly changed into political speeches and cheers. Suddenly I realized we were at a libertarian political rally. I never expected to end up at a Texan political rally with a bunch of Rubyists, but I had a good time.

Hopefully the next Ruby conference I attend with be as enjoyable as LSRC was, congrats to everyone who helped put the conference together and all those that attended the event and made it worth while.

Written by DanM

September 3, 2009 at 3:58 pm

Unit Testing Filesystem Interaction

Like most Rubyists, I write unit tests to verify the non-trivial parts of my code. I also try to use mocks and stubs to stub out interactions with systems external to my code, like network services.

For the most part, this works fine. But I’ve always struggled to find a good way to test interaction with the filesystem (which can often be non-trivial and therefore should be tested). On the one hand, the filesystem could be considered “external” and mocked out. But on the other hand, the filesystem is accessible when the tests run. In this way, the filesystem is sort of like a local database – it could be mocked out, but it doesn’t have to be, and there are tradeoffs to both approaches.

Over the past year or so, I’ve tried out a few approaches for testing interactions with the filesystem, each of which I’ll explain below. Since none of the approaches met my needs, Avdi and I built a new testing library, which I’ll introduce below.

Mocking the file system.

Sometimes, it is simplest to just mock the interaction with the filesystem. This works well for single calls to methods like




(these examples use Mocha):

File.stubs(:read).returns("file contents")

However, this approach breaks down when you want to test more complex code, which, of course, is the code you’re more likely to want to test thoroughly. For instance, imagine trying to set up mocks/stubs for the following method (which atomically rewrites the contents of a file):

require 'tempfile'

class Rewriter

  def rewrite_file!(target_path)
    backup_path = target_path + '.bak', backup_path) do |outfile| do |infile|
        infile.each_line do |line|
      FileUtils.cp(outfile.path, target_path)
  rescue Exception
    if File.exist?(backup_path), target_path)


Now imagine setting up those same mocks/stubs for each of the five or so tests you’d want to test that method. It gets messy.

Even more importantly, mocking/stubbing out methods ties your tests to a specific implementation. For instance, if you use the above stub (

File.stubs(:read).returns("file contents")

) in your test and then refactor your implementation to use, say,


, you’ll have to update your tests. No good.


MockFS is a library that mocks out the entire filesystem. It allows you write test code like this:

require 'test/unit'
require 'mockfs'

class TestMoveLog < Test::Unit::TestCase

  def test_move_log
    # Set MockFS to use the mock file system
    MockFS.mock = true

    # Fill certain directories
    MockFS.fill_path '/var/log/httpd/'
    MockFS.fill_path '/home/francis/logs/'

    # Create the access log '/var/log/httpd/access_log', File::CREAT ) do |f|
      f.puts "line 1 of the access log"

    # Run the method under test

    # Test that it was moved, along with its contents
    assert( MockFS.file.exist?( '/home/francis/logs/access_log' ) )
    assert( !MockFS.file.exist?( '/var/log/httpd/access_log' ) )
    contents = '/home/francis/logs/access_log' ) do |f|
      f.gets( nil )
    assert_equal( "line 1 of the access log\n", contents )

Although I suspect MockFS would be a great fit for some projects, I ended up running into issues.

First of all, it depends on a library (extensions) that can have strange monkey-patching conflicts with other libraries. For example, compare this:

require 'faker'
puts [].respond_to?(:shuffle) # true

to this:

require 'extensions/all'
require 'faker'
puts [].respond_to?(:shuffle) # false

Secondly, as you’ll notice in the above example, using MockFS requires you to use methods like


instead of just


. This works fine if you’re only testing your own code. However, if your code calls any libraries that use filesystem methods, MockFS won’t work.

(Note: There is a way to mock out the default filesystem methods, but it’s experimental. From the MockFS documentation:

“Reading the testing example above, you may be struck by one thing: Using MockFS requires you to remember to reference it everywhere, making calls such as instead of just As another option, you can use File, FileUtils, and Dir directly, and then in your tests, substitute them by including mockfs/override.rb. I’d recommend using these with caution; substituting these low-level classes can have unpredictable results. “)

All that said, MockFS is probably your best option if you’re only testing your code and you want to mock out files that you can’t actually interact with – for instance, if you need to test that a method reads/writes a file in


(although for the sake of testability, it’s generally good to avoid hardcoding fully-qualified paths in your code).

FakeFS is another library that uses this approach. I haven’t used it personally, but it looks quite nice.

Creating temp files and directories (with Construct)

Besides mocking the filesystem, another option is to have tests interact with actual files and directories on disk. The advantages are that the test code can be simpler to write and you don’t have to use any special filesystem methods.

Of course, as always, you want the test itself to contain all the relevant setup and teardown – you don’t want your tests to depend upon some set of files that have no explicit connection to the test itself (or create files that aren’t cleaned up).

To make this easy, we created a new library called Construct. Construct makes test setup simple by providing helpers to create temporary files and directories. It takes care of the cleanup by automatically deleting the directories and files that are created within the test. And because it creates regular files and directories, you can use plain old Ruby filesystem methods in your code and tests.

To install Construct, simply run:

# gem install devver-construct --source

Using Construct, you can write code like this:

require 'construct'

class ExampleTest < Test::Unit::TestCase
  include Construct::Helpers

  def test_example
    within_construct do |construct| 'alice/rabbithole' do |dir|
        dir.file 'white_rabbit.txt', "I'm late!"
        assert_equal "I'm late!",'white_rabbit.txt')


Let’s look at each line in more detail.

    within_construct do |construct|

When you call


, a temporary directory is created. All files and directories are, by default, created within that temporary directory and the temporary directory is always deleted before



The block argument (


) is a Pathname object with some additional methods (




, which I’ll explain below). You can use this object to get the path to the temporary directory created by Construct and easily create files and directories.

Note that, by default, the working directory is changed to the temp dir within the block provided to


. 'alice/rabbithole' do |dir|

Here we are using the


object to create a new directory within the temp directory. As you can see, you can create nested directories like


in one step. The block argument (


) is again a Pathname object with the same added functionality noted above.

Just like before, the working directory is changed to the newly created directory (in this case,


) within the block.

        dir.file 'white_rabbit.txt', "I'm late!"

Here we use the


object to create a file. In this case, the file will be empty. However, it’s easy to provide file contents using either an optional parameter or the return value of the supplied block:

within_construct do |construct|
  construct.file('foo.txt','Here is some content')
  construct.file('bar.txt') do
  The block will return this string, which will be used as the content.

As a more real-world example, here’s how you could use Construct to start testing the


method we looked at before:

require 'test/unit'
require 'construct'
require 'shoulda'

class RewriterTest < Test::Unit::TestCase
  include Construct::Helpers

  context "#rewrite_file!" do

    should "alter each line in file" do
      within_construct do |c|
        c.file('bar/foo.txt',"a\nb\nc\n")!('bar/foo.txt') do |line|
        assert_equal "A\nB\nC\n",'bar/foo.txt')

    should "not alter file if exception is raised" do
      within_construct do |c|
        c.file('foo.txt', "1\n2\nX\n")
        assert_raises ArgumentError do
!('foo.txt') do |line|
        assert_equal "1\n2\nX\n",'foo.txt')



You can learn more at the project page (both the README and the tests have more examples).

(As an aside, since Construct changes the working directory, it doesn’t play nicely with


. Specifically, if you place a breakpoint within a block, you’ll see the message “No sourcefile available for test/unit/foo_test.rb” and you won’t be able to view the source. If anyone knows an easy way to make


work with


, I’d very much appreciate some help!)


We’ve been moving our filesystem tests over to using Construct and so far have found it to be very useful. How do you test interactions with the filesystem? Do you use one of the above approaches, or something else? Or do you skip testing the filesystem altogether?

Written by Ben

August 25, 2009 at 9:51 am

Posted in Hacking, Testing

Tagged with , ,

Single-file Sinatra apps with specs baked-in

It’s so easy to create little single-file apps in Sinatra that it almost seems a shame to start a second file just for tests.  The other day Dan and I decided to see if we could create a Sinatra app with everything – including the tests – baked right in.  Here’s what we came up with.

#!/usr/bin/env ruby
require 'rubygems'
gem 'rack', '=0.9.1'
gem 'thin', '=1.0.0'
require 'sinatra'

get '/' do
  content_type 'text/plain'
  "Hello, world"

# Run me with 'spec' executable to run my specs!
if $0 =~ /spec$/
  set :environment, :test
  set :run,         false       # Don't autostart server

  require 'spec/interop/test'
  require 'sinatra/test'

  describe "Example App" do
    include Sinatra::Test

    it "should serve a greeting" do
      get '/'
      response.should be_ok
      response.body.should == "Hello, world"

    it "should serve content as text/plain" do
      get '/'
      response.headers['Content-Type'].should == 'text/plain'


view this gist
The code switches modes on the name of the executable used to run the file. If we run it with the


command, we get a test run:

$ spec -fs sinatra-tests-baked-in.rb

Example App
- should serve a greeting
- should serve content as text/plain

Finished in 0.007221 seconds

2 examples, 0 failures

Otherwise, if we call it as a Ruby program, it runs the Sinatra server as we would expect:

$ ruby sinatra-tests-baked-in.rb
== Sinatra/ has taken the stage on 4567 for development with backup from Thin
>> Thin web server (v1.0.0 codename That's What She Said)
>> Maximum connections set to 1024
>> Listening on, CTRL+C to stop

And there you have it: a true single-file application, specs and all.

Written by avdi

May 13, 2009 at 9:00 am

Posted in Development, Hacking, Ruby

Tagged with , ,