Blog Posts tagged with: ruby

Oct 16 2012


Introducing Word Magic

You might have noticed that we have a number of authors at Relevance. Some of us studied literature and linguistics. We are a wordy bunch. We're also kind of obsessed with time, so it's shouldn't be a surprise that we would be interested in how language evolves over time. Lucky for us, then, that Google has digitized every book they can get their scanners on and made that data available to the world.

Read More »

Sep 21 2012


Using Datomic from Ruby

We are all very jazzed at Relevance about Datomic. But so far, the people working on JVM projects have had all the fun, as Datomic's peer capabilities are exposed as a JVM library.

That changed a few weeks ago when the REST API for Datomic was announced. Suddenly, we have client access to Datomic from any language we choose. We quickly came up with a Ruby client for Datomic and an edn data reader and writer for Ruby. (edn is the data format Datomic uses for input and output, and by implementing edn in Ruby, we get to use native Ruby data to talk with Datomic.

Over the last two days, I've created a sample application using Ruby and Datomic. It is a wiki which saves all its data in Datomic and can read the history of pages from there, using only a few simple queries. The really interesting part is how easily we were able to use Ruby data structures in the place of edn to make easy-to-manipulate and easy-to-read schemas and queries. Here's the DB schema in Ruby:

[{:"db/id" => id(:"db.part/db"),
  :"db/ident" => :"page/name",
  :"db/valueType" => :"db.type/string",
  :"db/cardinality" => :"db.cardinality/one",
  :"db/fulltext" => true,
  :"db/doc" => "The name of a page.",
  :"db/unique" => :"db.unique/value",
  :"db/index" => true,
  :"db.install/_attribute" => ":db.part/db"
{:"db/id" => id(:"db.part/db"),
 :"db/ident" => :"page/text",
 :"db/valueType" => :"db.type/string",
 :"db/cardinality" => :"db.cardinality/one",
 :"db/fulltext" => true,
 :"db/doc" => "The text of a page.",
 :"db.install/_attribute" => ":db.part/db"

There are only a few differences between edn and this: mainly, edn keywords allow more characters than Ruby symbol literals, so we have to quote the symbols in Ruby.

Queries are even more fun:

datomic.query(dbname, [:find, ~"?id", ~"?name", ~"?text",
                       :in, ~"$db", ~"?name",
                         [~"$db", ~"?id", :"page/name", ~"?name"],
                         [~"$db", ~"?id", :"page/text", ~"?text"]],
                      :args => [{:"db/alias" => "example/wiki"}, name])

Given a variable name, this will pull back the DB id, name, and text for the page named that in Datomic. In this data structure, you'll notice one thing that probably isn't familiar to most Rubyists. The tilde (~) is used as a unary operator on strings to create edn symbols, which don't have an analog in Ruby. This capability is added by edn-ruby, our edn reader and writer.

To see the entire history of a page, we can write this query:

datomic.query(dbname, [:find, ~"?v", ~"?time", ~"?tx",
                       :in, ~"$cur", ~"$hist", ~"?uniq-attr", ~"?uniq-val", ~"?hist-attr",
                         [~"$cur",  ~"?e",  ~"?uniq-attr", ~"?uniq-val"],
                         [~"$cur",  ~"?tx", ~":db/txInstant", ~"?time"],
                         [~"$hist", ~"?e",  ~"?hist-attr", ~"?v", ~"?tx", true]],
                      :args => [
                        {:"db/alias" => dbalias},
                        {:"db/alias" => dbalias, :history => true},

Is this particularly Ruby-ish right now? No, not yet. Is it very cool? Yes, definitely. Datomic queries are built out of data structures: arrays, hashes, and other primitive data types, which allows us to easily use map, inject, and other Enumerable methods with them. A significant source of power and concision in queries comes from the use of not one, but two distinct data types for identifiers: symbols and keywords. Most languages cannot come close to this expressiveness, but Ruby handles it with ease. Ruby symbols can act as both identifier types, with the sly introduction of a unary operator "~" to distinguish them.

We have just begun to see what kind of amazing applications we can build with Datomic. Follow the Ruby Datomic client and the sample Ruby/Datomic wiki on Github to see what we come up with next.

Jun 15 2010


Rethinking PDF Creation in Ruby

Every now and then, a requirement will come up in a project, that will make me second guess my career choice as a programmer. It usually involves making me go through tedious exercises, never knowing if I'll end up where I want to be along the way.

This happened a couple of weeks ago when one of our projects called for generating PDF reports. The reports needed many stylized elements, layouts, and dynamic graphs. If you've ever generated PDFs in Ruby before, you know that it can be both tedious and difficult using the standard go-to PDF libraries out there. Let's face it, we're web developers. Coming from HTML+CSS-based layouts, writing Ruby code for that stuff is a major pain.

To give you an idea of how heavy it can get, here's an example taken from Prawn. The example was ironically called simple_table.rb.

  Prawn::Document.generate("simple_table.pdf") do 

  table([["foo", "bar " * 15, "baz"], 
         ["baz", "bar", "foo " * 15]], :cell_style => {:padding => 12}) do
    cells.borders = []

    # Use the row() and style() methods to select and style a row.
    style row(0), :border_width => 2, :borders => [:bottom]

    # The style method can take a block, allowing you to customize 
    # properties per-cell.
    style(columns(0..1)) { |cell| cell.borders |= [:right] }

  move_down 12

  table([%w[foo bar bazbaz], %w[baz bar foofoo]], 
        :cell_style => { :padding => 12 }, :width => bounds.width)


If you're scratching your head at this point, the code above generates a PDF with two simply styled tables. That's it. If you asked me to implement this in an app, I might have something half-way presentable in an hour. But, I could get a monkey, who just drank a whole bottle of scotch—don't ask about his drinking problem—to write two tables using HTML in less than 5 minutes.

A New Hope

Now some of you may be familiar with PrinceXML, which is a command line utility that will take HTML+CSS and give you back a beautiful PDF. It's even CSS2 compatible and passes the ACID2 test. Awesome. The only problem is that a single server license will set you back $3,800—which is prohibitively not awesome.

Being the open source zealots we are here at Relevance, we set out to find another solution. Tucked away in the internets, we stumbled across wkhtmltopdf. I know what you're thinking; awesome name, huh? wkhtmltopdf uses a WebKit rendering engine to make pretty PDFs out of HTML+CSS. Since it's leveraging WebKit, you get all the tasty CSS3 properties it supports. Ugly PDFs are suddenly a thing of the past.

Goodbye Prawn, Hello PDFKit

We were surprised that none of us had ever heard of wkhtmltopdf, considering how useful it is. When we looked for a Ruby library that leveraged it, we realized it didn't exist. Apparently not a whole lot of other people had heard of it either. That couldn't stand. A couple of open-source Fridays and several gallons of Mountain Dew later, we're excited to announce PDFKit, an open source library that makes working with wkhtmltopdf a snap.


Inline HTML+CSS => PDF

  kit ="<h1>Oh Hai!</h1>")
  kit.stylesheets << '/path/to/pdf.css'
  kit.to_pdf # inline PDF

HTML file => PDF

  html_file ='/path/to/html')
  kit =
  kit.to_pdf # inline PDF

Remote HTML => PDF

  kit ="")
  kit.to_pdf # inline PDF

What's the big deal?

If this hasn't sunk in yet, let's go over a quick list of wins this buys us:

  1. HTML+CSS - Assuming you're a web developer, there's a good chance that you already know HTML and can work with it efficiently.
  2. CSS3 - We get WebKit's CSS3 support for free. This means effects like drop shadows, rounded borders, transformations and others are super-easy. (Note: effects requiring blur radius do not work.)
  3. Testing - We have tools built into our normal workflow for testing HTML. You can even use Cucumber to drive the development of a PDF with PDFKit.

To give you an idea of how well this fits into our normal workflow here at Relevance, this is how we built out our PDF reports:

  1. Our designer mocked up a sample PDF and converted it to HTML+CSS.
  2. Using Cucumber to drive development, we created a controller action to generate this HTML view of the PDF. (It was just another URL in our app.)
  3. We added a screen-only stylesheet to the HTML that mimics the look of a PDF reader. This allowed us to get a feel of how it would look as a PDF.
  4. Using a bit of Rack Middleware that ships with PDFKit, we can get the PDF version of that web page by simply appending '.pdf' to the url.
  5. We're done. No crazy extra class to handle PDF rendering. No need to spend all day reading through docs to learn the obscure code and magic incantations required to generate your PDF.


  • PDF of - PDF rendered from
  • CSS3 Examples - Sample rendering of common CSS3 effects including border-radius, text-shadow, box-shadow, and border-image. Notice the lack of a blur radius on text-shadow and box-shadow.
  • Sample HTML page with PDF viewer CSS - Example of using a single HTML source to render both a screen version and a PDF version. Uses a media="screen" and media="all" to mark relevant CSS.
  • PDF generated from PDF viewer HTML - PDF generated from sample HTML above. You must tell PDFKit to only use print stylesheets in order to achieve this effect (, :print_media_type => true)).

Go Forth and PDF

I encourage you to take PDFKit for a spin, let us know what you think, and even submit some patches.

If you are pumped about the possibility of using PDFKit on a future project, then I've achieved my goal. If not, I'd ask you to think about what is missing, find out if it's already out there, and let us know how to make PDFKit even better.

Sep 30 2009


10 Must-Have Rails Plugins and Gems (2009 Edition)

When Paul Graham wrote that the "list of n things" is a degenerate case of the essay, our first thought was "Wow! That's for us!" And we're going one step farther: we're recycling an old "list of n things" essay from last year.

Seriously, we've been thinking of revisiting 10 must-have Rails plugins for a while now. There is a place for lists like that, and the Rails plugin and add-on space has been moving quickly. We are always looking for better ways to do things, so we try out a lot of the plugins that come along. Our list of favorites---the ones that we use on almost every project---is almost completely different than last year's model.

There's one important change in focus: the plugins and gems that are solely related to testing are gone from this list. Of course, that doesn't mean we're down on testing. On the contrary, we built RunCodeRun because we think testing is so vital. We're saving the testing tools for the RunCodeRun blog; we'll be writing another degenerate essay there as a counterpart to this one.

There are numerous other plugins we use for special needs, such as PDF generation or attachment handling. But our favorites are the ones that we use on almost every project. So here they are, along with brief comments explaining why you want to check them out:

  • Inherited Resources: eliminates most of the boilerplate code from our controllers. (The new controller responder feature in Rails 3 is similar in intent.)
  • Formtastic: takes most of the pain out of writing the markup for HTML forms. (Together, Inherited Resources and Formtastic make a nice alternative to scaffolding frameworks like Streamlined and ActiveScaffold.)
  • CapGun: provides easy build notifications (see this previous post for more info).
  • Faker: helps us generate fake data. We use it for testing, but mostly for providing demo data for development and staging environments.
  • Clearance: feature-rich authentication and signup.
  • Safe ERB: helps ensure that our apps are not vulnerable to cross-site scripting attacks. (We look forward to similar functionality being baked into Rails 3.)
  • RedHill on Rails Core: we use this primarily to declare foreign key references in our database schemas. Telling the database about table relationships adds a small cost to our projects, but we've found that the benefits outweigh that cost. (It's unclear where this plugin lives at the moment, but there are numerous forks of it on GitHub.)
  • RPM: Rails Performance Management from New Relic; wonderful for discovering and diagnosing performance problems.
  • will_paginate: the nicest, easiest pagination plugin we've seen.
  • hoptoad: great, customer-friendly notifications about exceptions that happen in the app.

Don't reinvent the wheel! Use these plugins (or others like them), and definitely consider contributing to them if they fall short of what you need!

Sep 23 2009


Quick and Easy Logging with LogBuddy

Good logging is crucial for effective problem diagnosis in production. Plus, easy logging remains a terrific debugging technique during development. As helpful as "real debuggers" are, sometimes a debugging log statement is exactly what you need to find a problem quickly.

LogBuddy is a little gem that makes good logging easier. It helps even in Rails, which already has good logging support, and it's a bigger help when building gems and standalone Ruby apps, where you have to start from scratch with logging.

What does LogBuddy do for you that Rails doesn't already? There are numerous small features, but here are the big ones:

  1. It ensures that logger is available everywhere, not just in classes that extend parts of the framework.
  2. It makes it extremely easy to add informative debugging messages with annotated output and full exception info.

Installing and Adding LogBuddy to Your Project

To install the latest release of LogBuddy, just install the gem:

$ gem install relevance-log_buddy --source

Then add a require 'log_buddy' statement to your app. If it's a Rails app, it's best to add this to environment.rb:

  config.gem 'relevance-log_buddy',
             :source => "", 
             :lib => "log_buddy"

Finally, initialize LogBuddy. In Rails apps, we usually put this in config/initializers/logging.rb:


(You can pass some options to LogBuddy.init; we'll get back to that in a bit.)

LogBuddy creates and initializes a logger for the app to use. In Rails apps, it simply uses RAILS_DEFAULT_LOGGER unless you tell it differently.

Using LogBuddy

LogBuddy mixes a couple of methods into every object in the system: logger and d. Here's how they work.

The logger method is no surprise at all. It simply returns the Logger instance, and you can log by calling debug, info, warn, error, or log methods on it. LogBuddy's logger doesn't usually do anything special; the benefit is that, since it's mixed into Object, it's available everywhere, automatically. (In a typical Rails app, there are numerous contexts where logger doesn't work, and you have to explicitly use RAILS_DEFAULT_LOGGER.)

My personal favorite LogBuddy feature is the d method. Like logger, it's available everywhere. But the d method is designed just for debugging messages. You can call it with an explicit string, or with some object you want to see the value of:

  d some_exception
  d result

Strings are logged the same way logger.debug would do it. Exceptions are logged with all of the information you might want: the message, exception class name, and backtrace. Finally, if you pass any other object, d calls that object's inspect method and logs the resulting string.

Where d really shines is when you want to log several values at once, with annotations to distinguish them. Just pass a single-line block to d, like this:

  d { first; current; last}

That produces these three log lines:

  first = "foo"
  current = "bar"
  last = "baz"

The values you log can be any Ruby expression:

  d { 3; name; @model; RAILS_ENV; options[:limit] }

and you'll get just what you want out of that:

  3 = "3"
  name = "primary"
  @model = #<Contact id: 14, name: "Joe">
  RAILS_ENV = "development"
  options[:limit] = 5

There are some restrictions if you use this feature. The entire call to d must fit on one line, and you must use the curly-brace style of block, rather than the do/end style. Finally, if you want to log multiple values, separate them with semicolons, not commas.

(You may be wondering how LogBuddy accomplishes that trick. The answer is left as an exercise for the reader ... especially since there are some hints in the restrictions just mentioned. Of course, you can always read the source.)

LogBuddy Initialization Options

The LogBuddy.init method takes an options hash. Here are the permissible options:

  • :logger -- you can supply a logger instance for LogBuddy to use. If you don't supply one, LogBuddy uses RAILS_DEFAULT_LOGGER if it's defined; otherwise, it creates a new logger that writes to standard output.
  • :log_to_stdout -- by default, messages from the d method are logged (using logger.debug) and also written to standard output. Set this option to false to only use the logger.
  • :disabled -- set this option to true to turn off the output from the d method. It's common to set it this way:
    LogBuddy.init :disabled => Rails.env.production?
  • :log_gems -- if you set this option to true, LogBuddy watches gem activation and logs information about each gem. This can be useful for tracking down gem activation errors

Try It Out!

LogBuddy is really easy to set up, and then it's there when you need it most: when you're focused on a problem and just need to get the details quickly. Please try it and let us know what you think!

Sep 16 2009


Easy Build Notifications with CapGun

Most of us get notified about lots of little events on our projects: Commits, build failures (and fixed builds), and runtime exceptions, for example. But deployment is where the rubber meets the road on web development projects. Deployment to staging means new functionality to try out and test, and of course deployment to production is even more important.

CapGun is a gem we use to send email notifications whenever we deploy one of our projects. It works with Capistrano and uses ActionMailer to let every interested party know when a deployment happens.

Here's how to work with CapGun in a Rails project. Add this to config/environment.rb:

  config.gem 'relevance-cap_gun', 
             :source => "", 
             :lib => "cap_gun"

Then install and unpack the gem:

  $ rake gems:install
  $ rake gems:unpack

Finally, edit your deployment script (usually config/deploy.rb) and add this:

  require File.join(RAILS_ROOT,

  set :cap_gun_action_mailer_config, {
    :address => "",
    :port => 587,
    :user_name => "", # deploy bot email address
    :password => "outtacontrol",  # deploy bot email password
    :authentication => :plain 

  set :cap_gun_email_envelope, {
    :recipients => %w[], 
    :from => "Foo Project Deployment Bot <>"

  after "deploy:restart", "cap_gun:email"

We usually use GMail as our MTA for this purpose, and CapGun includes support for secure, authenticated email connections so that you can do the same. It's best to create a special-purpose, throwaway email account just for things like this; that way there's little risk in putting the email password in the project deployment script. (But there's also nothing stopping you from reading it from another file that's not checked into source control, just like you would do with your production database passwords. The deploy.rb file is just Ruby code, after all. And if the source is going to be in a public repository, you should definitely do that.)

The deployment email has a brief summary at the top (in fact, the subject often tells you all you need to know). But there are useful details in the body. Here's an example of what you might see from the configuration above:

From: Foo Project Deployment Bot <>
Date: Tue, 15 Sep 2009 17:27:57 -0400
Subject: [DEPLOY] fooproj deployed to production

fooproj was deployed to production by george at September 15th, 2009 5:27 PM EDT.

Nerd details
Release: /var/apps/fooproj/releases/20090915212721
Release Time: September 15th, 2009 5:27 PM EDT
Release Revision: 69246739f2a1cbcef5ca76f1842c21849db7778a

Previous Release: /var/apps/fooproj/releases/20090915194707
Previous Release Time: September 15th, 2009 3:47 PM EDT
Previous Release Revision: 9ceb19b1777470d1d5133f433fdd5d1873c7a4c0

Deploy path: /var/apps/fooproj
Branch: main

Commits since last release
d37a15c:who put a blink tag in here?
f1b603e:Added favicon

Setting up CapGun only takes a few minutes, and you'll love the increased visibility into your team's deployments. (And even if you're a team of one, you'll appreciate having the emails as a record of your deployments.) Try it out, and let us know what you think!

Jul 29 2009


Working With Multiple Ruby Versions Has Never Been This Easy

The Ruby VM market is thriving, and we increasingly find ourselves spending the morning in JRuby and the afternoon in Ruby Enterprise Edition. Or Thursday using Leopard Ruby and Friday using Ruby 1.9. Or ... well, you get the idea. So we needed a lightweight tool that eliminates the cost (in both time and frustration) of switching between Ruby versions. We wanted something drop-dead simple. Meet the Ruby Switcher.

Ruby Switcher

Hello, Ruby Switcher

The Ruby Switcher debuted earlier this year as a means for toggling between a handful of pre-installed Ruby versions. And once you bit the bullet and manually installed those VMs, and assuming you installed them in the "right" location, the Ruby Switcher offered crazy-fast switching between those few Ruby versions. But we're passionate about continuous improvement and maintaining a sharp set of tools, so we recognized that switching Ruby versions was Step 2; Step 1 (i.e., installing those Ruby versions in the first place) needed a healthy dose of automation as well. Today's Ruby Switcher makes both steps insanely simple, and it adds support for more (and newer) Ruby versions as well.

Pick a Ruby, Any Ruby

Enough talk! Let's download the Ruby Switcher and get this party started.

  curl -O -L
  echo "source ~/" >> .bash_profile
  source .bash_profile

That's it. Let's quickly verify that you have your platform's core developer tools installed, and then you'll be ready to put the Ruby Switcher to work.

Prerequisites - Compilers, Libraries, and Whatnot

If you're on OS X, you'll need to download and install Xcode. (If you just want to switch between Leopard Ruby and JRuby, you can skip this step. If you want to use any other versions of Ruby, you'll need Xcode.)

If you're using Ubuntu, use apt-get to grab a few essential packages:

  sudo apt-get update
  sudo apt-get install build-essential zlib1g-dev libreadline5-dev libssl-dev

For other *nix variants ... well, clearly you enjoy figuring this stuff out.

Ruby 1.9

Yehuda Katz recently asked the Ruby community what we need in order adopt Ruby 1.9. Having an easy way to experiment with Ruby 1.9 is surely a good place to start. What could be easier than a single command?


The installation will take a few minutes. In the meantime, why not check out Bruce Williams' slides on Ruby 1.9 from last year's Lone Star Ruby Conference — Ruby 1.9: What's New and Why it Matters?

  checking build system type... i686-pc-linux-gnu
  checking host system type... i686-pc-linux-gnu
  checking target system type... i686-pc-linux-gnu
  checking for gcc... gcc
  installing rdoc
  Using ruby 1.9.1p129 (2009-05-12 revision 23412) [i686-linux]
  Successfully installed rake-0.8.7
  1 gem installed

By the time you're done reading through the Ruby 1.9 highlights, you'll be ready to take it for a spin. Type ruby -v to verify that you're rockin' with 1.9.1.

  ruby 1.9.1p129 (2009-05-12 revision 23412) [i686-linux]


Installing and using JRuby is just as easy.

First, be sure that you have the JDK installed. If you're using OS X, you're all set. If you're on Ubuntu, you can install it with apt-get. (For other Linux distros, you can ask your native package manager for the JDK bits.)

  sudo apt-get update
  sudo apt-get install sun-java6-jre sun-java6-jdk

With the JDK in place, installing JRuby is a cinch.


Verify the results with ruby -v.

  jruby 1.3.1 (ruby 1.8.6p287) (2009-06-15 2fd6c3d) (Java HotSpot(TM) Client VM 1.6.0_10) [i386-java]

Wait a minute: shouldn't we have typed jruby -v instead of ruby -v? Sure you can do that if you really want to. But we're not big on having to remember to type jirb instead of irb, or jgem instead of just gem, etc. Once we tell the shell to use JRuby, we want the normal Ruby commands to just work. The Ruby Switcher ensures that they do.


Looking for yet another Ruby version? See what else the Ruby Switcher has to offer:

  • install_ree_186
  • install_ruby_186
  • install_ruby_187
  • install_jruby_120

And if you find yourself wanting some other Ruby variant, be sure to check out the Ruby Switcher's internals; you can likely adapt one of the existing installation functions to meet your exact need.

Willy-nilly Switching

Once you have the desired Ruby versions installed, switching between them couldn't be easier. Each of the install commands comes with a corresponding use command to instruct your shell to switch to the specified Ruby version:

Install It Use It
install_ruby_191 use_ruby_191
install_ruby_186 use_ruby_186
install_ruby_187 use_ruby_187
install_jruby use_jruby
install_jruby_120 use_jruby_120
install_ree_186 use_ree_186
N/A [1] use_leopard_ruby

And these commands are shell-specific! So while one terminal window is using Ruby 1.8.7 to run your front-end Rails app, you can have another terminal using JRuby to run your back-end messaging code.

Ruby 1.9, the Community, and You

Want to see whether your app runs on Ruby 1.9? Flip your shell to use_ruby_191 and try it out. It's that kind of experimentation that will allow the Ruby community to make the migration to Ruby 1.9.

See a problem with a certain gem on Ruby 1.9? Let the gem author know about it and chime in at Better yet, write a test that proves the bug and pass that test along to the author. Better still, fix the issue and submit a patch. Any one of these steps moves us forward, and all the while you've still got your default Ruby installation standing safely by for your day job.

When switching between Ruby versions is this seamless, there's no reason not to experiment.


[1] Ruby is installed by default on OS X Leopard, so there's no need for an install_leopard_ruby command.

Image courtesy of bdu ( [Creative Commons License]

Apr 01 2009


Micronaut: Innovation Under the Hood

Last week, Rob announced Micronaut, our new BDD framework written by Chad Humphries. I’ve been itching to write about Micronaut as well, and my take on it is similar to Rob’s, although I start with a very different perspective.

It’s a little surprising that I’m excited about Micronaut. I’m sort of a Ruby old-timer, and I’ve never been that excited about RSpec or any of the other Ruby test frameworks that have appeared over the last few years. Yes, they offer some advantages in some cases, but I’ve always seen the improvements as incremental rather than revolutionary. I like RSpec’s facilities for structuring tests, but should never struck me as a radical improvement in expressiveness. In fact, I frequently run into situations where I think a well-crafted assertion is much clearer than a should expression.

I just never got the BDD religion, in other words.

What I like about Micronaut is that its innovation is mostly under the hood, rather than on the surface. Rather than designing some new variation on how we express our tests, Chad opted for RSpec compatibility and built a really nice engine for loading and running RSpec-style tests. Architecture matters, and Micronaut’s architecture is a joy.

First of all, as Rob noted, Micronaut is small, easy to understand, and fast. That makes it fun to hack on, and great to use on projects. It also gives me confidence; simple tools tend to be more robust, and I want that in my testing tool.

Second, Micronaut’s architecture provides a lot of flexibility. To illustrate that, while attending talks at QCon a couple weeks ago, I added test/unit compatibility to Micronaut. Here’s a short example that mirrors Rob’s example from last week, but in a test/unit style:

  require 'micronaut/unit'

  Micronaut.configure do |config|
    config.filter_run :focused => true

  class MicronautMetadataTest &lt; Micronaut::Unit::TestCase

    # 'testinfo' allows declaring metadata for a test, and works
    # like Rake's 'desc' method: it applies to the next test.

    testinfo :focused => true
    def test_this_will_definitely_run    
      assert self.running_example.metadata[:focused]

    def test_this_never_runs
      flunk "shouldn't run while other specs are focused"

    testinfo :pending => true
    def test_this_is_pending

    testinfo :speed => 'slow'
    def test_too_slow_to_run_all_the_time
      assert_equal 4, 2+2

I don’t know how interesting test/unit compatibility is in its own right. I certainly wouldn’t claim that the example above is superior to the RSpec equivalent. But it was a fun exercise to really prove Micronaut’s design. It only took a few hours (of partial attention) and it clocks in at under 200 lines of code (plus `assertions.rb` from the test/unit codebase). I love the idea of the testing API and the test execution engine not being so tightly coupled. And it might be very useful if you have existing tests written with test/unit and you’d like to gain the benefit of Micronaut’s metadata support.

Which brings me to Micronaut’s best feature. Almost all unit-testing frameworks incorporate some support for test suites, but suites have never lived up to their promise. It would be nice to have tests organized in suites for distinct purposes, but the setup and maintenance costs associated with suites have meant that very few teams make good use of them. Micronaut’s metadata is a different—and much better—solution to the same problem. As some have noted, the idea is similar to Cucumber’s support for tags. Just attach metadata of your choice to Micronaut tests or examples, and then you can use that metadata to select what tests are run in different situations.

At the moment, test/unit compatibility is only available in my fork of Micronaut. It allows using RSpec-style describe and it blocks alongside test/unit-style test methods, and supports test blocks à la Context and ActiveSupport. I don’t think we’ll pull this completely into Micronaut; I think it would work better as a separate gem. But I’d love to get your feedback about the whole idea.

Nov 10 2008


RunCodeRun at the Professional Ruby Conference

I will be bringing RunCodeRun Beta invites to the Professional Ruby Conference in Boston next week. If you are attending the conference, and want to get your open source Ruby project configured for free Continuous Integration on RunCodeRun, come and see me.

If your build goes green, I will have a T-shirt for you (while supplies last).

Once you go green, you don't go back.

Nov 25 2005


Building the Enterprise Hammer, Part 3

In this installment we are going to dig further into Idea #3 from Building the Enterprise Hammer:

The transition from EJBs to POJOs is only a halfway point. We now need to leave Plain Old Static languages (POSs) behind.

Developers have already rejected "special hammers" (past versions of EJB), in favor of plain old hammers. This is a great step towards more flexible applications. However, they still typically mount their hammers in some kind of frame (e.g. Spring). What happens when this frame is not perfectly adapted for the task at hand, or when the task at hand changes?

Let's say, for example, that we wanted to repurpose our Enterprise Hammer as an Enterprise Window Washer, by installing different attachments. We believe that this should work because:

  • Windows are regularly spaced on the side of the building.
  • Window spacing has a known relationship to the spacing of nails hammered by the Enterprise Hammer.

This is an example of refactoring to generality: finding similarities so that you can cheaply provide a new function (washing windows) through the same mechanism that provided the original function (driving nails).

Java makes this kind of generalization difficult. Java encourages up-front rigor about the type of an object. If you decide later than the "Hammer" type can be generalized to "Widget", you may have to touch hundreds or thousands of lines of code to enact that change. Duck-typed languages, such as Ruby and Python, encourage less assumptions. And, the assumptions are easier to change later. This is one place where the 10x hype is real.. Duck-typed languages can be an order of magnitude more productive, in both developer time and lines of code, when designing for (or refactoring to) generality.

There's another issue here, as well. Our Enterprise Window Washer may require changes to the frame itself, since windows are spaced differently than nails, and washing requires a different motion than hammering. But, we didn't build the frame. What are our options? Many languages provide a simple solution through open classes. With open classes, our own application code can make spot modifications to the frame to suit our specific needs. Conversely, Java discourages this flexibility in two ways:

  • deliberately, by closing classes
  • inadvertently, through its complex deployment model

As a result, Java developers may learn to not even see opportunities for reuse. Elegant solutions are not only not chosen, they are not even considered.

But More Flexible Languages are Dangerous!

Yes. There are many good reasons that Java became dominant, instead of e.g. Smalltalk. Understand those reasons, and you'll also know why it's time for a change. Stay tuned for the next installment.

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