Posts Tagged ‘ruby’

Array.to_hash() in Ruby

Tuesday, August 4th, 2009

I often find myself wanting this method. This is my 3rd or 4th writing of it – it’s shorter this time. Inject is my new best friend.

class Array
  def to_hash
    inject({}) {|hash, i| hash[i[0]] = i[1]; hash}
  end
end

What this snippet does is take an array and turn it into a hash, like so

[["apple", 1], ["banana", 2], ["citrus", [3,4,5]] => 
    {"apple" => 1, "banana" => 2, "citrus" => [3,4,5]}

If I didn’t have to deal with the case where there may be subarrays, I’d use nick’s approach

Hash[*self.flatten]

My solution isn’t that much more code, and handles the case of subarrays.

Update

Ola makes the good point that this is actually the best of both worlds :

Hash[*self.flatten[1]]

Thanks Ola. …I still think inject is cool, though :) .

Stop running test:unit tests when using rspec

Friday, January 16th, 2009

You know those 3 lines that show up every time you do an rspec run?

/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby -Ilib:test "/Library/Ruby/Gems/1.8/gems/rake-0.8.3/lib/rake/rake_test_loader.rb"  
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby -Ilib:test "/Library/Ruby/Gems/1.8/gems/rake-0.8.3/lib/rake/rake_test_loader.rb"  
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby -Ilib:test "/Library/Ruby/Gems/1.8/gems/rake-0.8.3/lib/rake/rake_test_loader.rb"

…yeah, those lines. I hate those lines.

So let’s get rid of them!

Each of those lines is rails trying to run test:unit. RSpec replaces the default rake target by doing this:

task :default => :spec

BUT If you’ve played with rake before, you know that this doesn’t actually replace the default target, it only adds to it. We need to remove the default target then point it at :spec

Turns out that’s not too hard. Put this code (got it from here) at the end of your Rakefile:

Rake::TaskManager.class_eval do
  def remove_task(task_name)
    @tasks.delete(task_name.to_s)
  end
end
 
Rake.application.remove_task("default")
 
task :default => :spec

You’re all set!

Eventual Consistency, or things will all work out…eventually

Tuesday, August 5th, 2008

So we’re working with Amazon’s SimpleDB. It’s pretty sweet, though the ruby libraries for it are still a bit primitive. One of the problems you run up against when you’re writing integration tests against it is eventual consistency.

Take this test :

it "should save" do
  customer = Customer.create!(:name => 'bob', :email => 'bob@example.com')
  customer = Customer.find(customer.key)
  customer.name.should == 'bob'
end

The way SimpleDB works, you’re assured that Customer.find will work…eventually, but not right away.

For a couple days we contented ourselves to just run the integration tests a couple times until they didn’t error out. But that got old.

Enter “eventually” :

it "should save" do
  customer = Customer.create!(:name => 'bob', :email => 'bob@example.com')
  customer = eventually { Customer.find(customer.key) }
  customer.name.should == 'bob'
end

It’s a very simple method (below) that just retries the passed in block until it succeeds, timing out after 10 tries. Super simple, works like a charm. Thank you ruby.

Here’s the source :

def eventually(tries = 0, &block)
  yield
rescue
  raise if tries >= 10
  sleep 0.5
  eventually(tries + 1, &block)
end

I will say, I can’t help but smile every time I write “eventually” in a test… :)

Clickable Stack Traces on your Rails Error Page

Wednesday, April 30th, 2008

Wouldn’t it be nice if when an error happened in your application, you could not only see the stack trace, but click on a line and jump to the offending code? This is not groundbreaking stuff, I know, I had this like 10 years ago in C++ and later Java fat clients, and I’m sure other languages & IDEs had it too – but somehow in moving to writing web apps in Ruby, I lost it.

I want it back damnit!

Turns out it’s pretty easy to get back (at least it is if you use textmate) – check it out.

Custom Error Page

First, to get a custom error page for your project, add something like this to your application.rb :

def rescue_action_locally(*args)
  render :template  => "application/public_error", :layout => false
end
 
alias rescue_action_in_public render_action_locally

Note, if you’re using exception notifiable, you probably want to change the last line to something like :

alias render_404 rescue_action_locally
alias render_500 rescue_action_locally

We use markaby, so our public_error template looks something like this; it’s probably a good idea to keep this simple and not use a layout, just in case the error came from the layout :

html do
  head do
    title action_name
    stylesheet_link_tag 'error'
  end
  body do
    div.error do
      div.message do
        h1 "Whoops"
 
        p "We detected an error.  Don't worry, though, 
we've been notified and we're on it."
      end
    end
  end
end

Adding a Stack Trace w/ Links to the Error Page

So, it would be helpful to us for our error page to tell us more in our development and staging environments. We do use exception notifiable, so we don’t actually need or want it to say anything else to a real user in production. Adding this to our template, it now looks like this :

html do
  head do
    title action_name
    stylesheet_link_tag 'error'
  end
  body do
    div.error do
      div.message do
        h1 "Whoops"
 
        p "We detected an error.  Don't worry, though, 
we've been notified and we're on it."
      end
 
      if RAILS_ENV != 'production'
        div.stack_trace do
          h2 "Stack Trace"
          div { link_to_code $!.to_s.to_s.gsub("\n", "
") }
          hr
          div { link_to_code $!.backtrace.join("
") }
        end
      end
    end
  end
end

What’s that “link_to_code” method in there?

It’s a method in application_helper that replaces any path with a textmate url to open up that file on your local system and jump to the offending line. Check it out :

def link_to_code(text)
  text.gsub(/([\w\.-]*\/[\w\/\.-]+)\:(\d+)/) do |match|
    file = $1.starts_with?("/") ? $1 : File.join(RAILS_ROOT, $1)
    link_to match, "txmt://open?url=file://#{file}&line=#{$2}"
  end
end

That’s it. Suddenly, stack traces are friendly again!

Pretty Printing Seconds in Ruby

Tuesday, October 16th, 2007

I must have written various versions of this code 20 times so far in my career, but never so quickly and cleanly. I love ruby.

    min, sec = sec / 60, sec % 60
    hour, min = min / 60, min % 60
    day, hour = hour / 24, hour % 24
    week, day = day / 7, day % 7
 
    [
      week > 0 ? "#{week} weeks" : nil,
      day > 0 ? "#{day} days" : nil,
      hour > 0 ? "#{hour} hours" : nil,
      min > 0 ? "#{min} minutes" : nil,
      sec > 0 ? "#{sec} seconds" : nil
    ].compact.join(", ")

The really cool thing is the multiple assignment that ruby lets you do. I haven’t used it for something exactly like this before, but I do use it often and it’s really nice.

I feel like there should be a better way to do the bottom half of this, but this is pretty damn readable, I think. You might have to have a little rubyFU to remember what compact does – which is get rid of the nils.

Anyway, this was about 15 minutes of work (and I did it test first).

Customizing Markaby – Language Level Refactorings

Wednesday, September 26th, 2007

It’s very easy to call out to methods in markaby, but it’d be nice if you could actually customize the dsl as well.

For example, on many of our pages we have a bottom row that has buttons that look a certain way. So on every page, we have :

  table(:width => "100%") do
    tr do
      td.left do
        previous_button
        first_button
      end
      td.center do
        print
      end
      td.right do
        next_button
        last_button
      end
    end
  end

The code for the actual buttons changes, and after a few tries to extract the whole thing into a single method, we gave up. Our efforts had made it harder to read, not easier. There was always just a little too much variance, and it didn’t feel right.

What we really wanted to write was :

  last_row do
    column do
      previous_button
      first_button
    end
    column do
      print
    end
    column do
      next_button
      last_button
    end
  end

This lets the buttons that change all stay in the view, and gets rid of the skeleton and positional stuff that doesn’t change. Furthermore, it’s DRY and puts all that positional logic in one place instead of scattered across 20 views.

How to do this?

I wrote a test (in RSpec) that looks something like :

describe ApplicationHelper do
  it "should generate a table from a buttons method" do
    last_row(:columns => 2) do
      column do
        "foo"
      end
      column do
        "bar"
      end
    end.should == '<table width="100%"><tr>' +
                    '<td class="left">foo</td>' + 
                    '<td class="right">bar</td>' +
                  '</tr></table>'
  end
end

After a bunch of fiddling and poking around, I finally made the test (and a couple others) pass with this code in my ApplicationHelper :

def last_row(options, &block)
  markaby do
    table(:width => "100%") do
      tr do
        LastRowContext.new(self, options[:columns]).
                                  instance_eval(&block)
      end
    end
  end
end
 
class LastRowContext
  def initialize(markaby, columns)
    @markaby, @column_count, @column_index = 
                            markaby, columns, 0
  end
 
  def column(&block)
    alignment = case @column_index += 1
    when 1 : :left
    when @column_count : :right
    else :center
    end
 
    @markaby.instance_eval do
      td(:class => alignment, &block)
    end
  end
end

I’m sure this could get cleaned up more; this was the work of less than an hour. In particular, if you did this often, you could extract a common MarkabyContext superclass that had some convenience methods. The point is, this is really easy to do, and we shouldn’t be scared to try “Language level refactorings” like this.

Daemonizing a Ruby Script in Rails

Thursday, September 20th, 2007

This took way longer than it should have, so I thought I’d jot down what I did so it might take less time next time.

1. Install the daemons gem

sudo gem install daemons

2. Presumably you have a script that looks something like this already

#!/usr/bin/env ruby
require File.dirname(__FILE__) + "/. ./config/environment"
 
SchedulerDaemon.new.run

This is a scheduler script that lives in the scripts directory of a rails project.

3. You’re going to take this code and wrap it in daemon stuff, like so

#!/usr/bin/env ruby
RAILS_ROOT = File.expand_path(File.dirname(__FILE__) + '/. .')
 
require 'rubygems'
gem 'daemons'
require 'daemons'
 
Daemons.run_proc("scheduler", 
                 :log_output => true, 
                 :dir_mode => :normal, 
                 :dir => "#{RAILS_ROOT}/log") do
  require File.join(RAILS_ROOT, "config/environment")
  SchedulerDaemon.new.run
end

The really hard part for me was debugging it. Which meant figuring out how to get logging going. With this code, you can just tail “log/scheduler.output” and see the contents of any puts in the code. Once I started doing that, everything else was easy.

RAILS_ROOT has to be set first, because daemons changes the current working directory. Also, I use the log dir, because it’s shared by capistrano, so I can deploy, then stop / start my scheduler and not worry about losing my first pid file – plus that’s where logs are supposed to go.

4. To make my life just a little easier, I also added some debugging statements

Daemons.run_proc("scheduler", 
                 :log_output => true, 
                 :dir_mode => :normal, 
                 :dir => "#{RAILS_ROOT}/log") do
  begin
    require File.join(RAILS_ROOT, "config/environment")
 
    puts "starting scheduler at #{Time.now} for #{RAILS_ENV}"
    SchedulerDaemon.new.run
 
  ensure
    puts "ending scheduler at #{Time.now}"
  end
end

This was actually pretty easy, and next time it will take 5 minutes to create a daemon. Nice gem.

More Fun with Times, Mocks, and Closures

Thursday, May 24th, 2007

I solved a complex problem in cruise today with some non-trivial mocking. Check this one out :

I needed to test that every x amount of time, we do a clean checkout. It can be every 6 hours, 2 days, whatever. How do you test this?

Well, maybe you could mock the time.

Time.stubs(:now).returns(Time.now + 2.hours)

That almost works, except that the code works by touching a file. And touch doesn’t use Time.now. Now at this point, we could go crazy, and mock FileUtils.touch, of course that means we’ll also have to mock File.exists? and then what are we really testing?

Instead, I used Mocha to temporarily replace FileUtils.touch with my own implementation that acts like the original but uses my own value of time. It looks like this so far.

  marker = sandbox.root + '/last_clean_checkout_timestamp'
 
  now = Time.now
  FileUtils.stubs(:touch).with(marker).returns(proc do
    File.open(marker, 'w') {|f| f

you’ll notice that both of these stubs are returning procs that reference now a local variable….

That’s ruby magic.

It means that I can now forget about mocks and write the rest of my test like this :

  @project.do_clean_checkout :every => 1.hour
 
  assert @project.do_clean_checkout?
  assert !@project.do_clean_checkout?
 
  now += 59.minutes
  assert !@project.do_clean_checkout?
 
  now += 2.minutes
  assert @project.do_clean_checkout?
  assert !@project.do_clean_checkout?
 
  @project.do_clean_checkout :every => 2.days
  now += 1.day + 23.hours
  assert !@project.do_clean_checkout?
 
  now += 2.hours
  assert @project.do_clean_checkout?

Instead of changing the mocks several times in between each test, I can just change my local variable now. Because of closures, the mocked out methods return the new value.

Ruby is awesome (and Mocha is pretty sweet too)

Object Mother…in rails?

Tuesday, March 6th, 2007

That’s right, the circa 2000 pattern still makes sense today. Use an “object mother” as a test factory to conveniently create objects for your unit tests to bang against. It will often default values, or have different states in which to create objects. For example, you might have a new_user, as well as a new_superuser and new_guest method all of which return users.

Read about the original pattern

But why, you ask, not just use rails’ fixtures? Glad you asked.

  1. it’s more intuitive and maintainable to setup the data you need right next to the test
  2. it’s easier to create just exactly the objects you need when you have test factory methods

But don’t take my word for it. Let’s look at some code.

First off, what does this look like in ruby? I am creating an “ObjectMother” module, which I then just mixin to my tests. A test might then look like :

  include ObjectMother
 
  def test_delete_project
    project = new_project('foo')
    post :delete, :id => project.id
    assert_raise(ActiveRecord::RecordNotFound) { Tag.find(project.id)}
  end

The magic is in “new_project”. It’s an entirely pragmatic construct. If you pass it a string, it will set everything else to acceptable defaults, and use that string as a name. It looks something like this.

module ObjectMother
  def new_project(options)
    options = {:name => options} if options.is_a? String
    options[:url_name] = options[:name].gsub(/\W/, '') if !options.has_key?(:url_name)
    Project.create!(options)
  end
 
  ...
end

Here in project, it defaults the url_name (which must be unique) from the name you’ve given it. However, you could also create a more custom project by running this :

  new_project(:name => 'garage', :url_name => 'the_garage', :description => 'foo')

This is how it works for projects, but it’s only purpose in life is to make my life easier and reduce the amount of code one has to type or read. So each type of thing it creates works a little bit differently according to our needs
——
h2. A more complicated example

I was playing with ferret last week, and wrote a test that looked like this :

  def test_across_types
    project = new_project('rabbit holes')
    post = new_post(:subject => 'a rabbit has a big head')
    user = new_user(:display_name => 'rabbit head')
 
    @search.string = 'rabbit'
    assert_find [project, post, user]
 
    @search.string = 'rabbit head'
    assert_find [post, user]
  end

My thought process was something along the lines of :

  1. I want to test that my searcher works across types
  2. I need to create a project, post, and user that all have a term in them (in different places)
  3. I want to search for the term, and make sure i get all of them
  4. I want to search for a term that maybe 2 of them have and make sure I only get those 2

Writing the test for this part literally took 30 seconds, I didn’t have to go lookup the fixtures or add a new fixture for my new case. I also didn’t have to remember all the things that it takes to make a valid project or post or user.

Helpful Additions To Test::Unit

Tuesday, March 6th, 2007

Doing a lot of rails work, I’m getting a good feel for testing in ruby and rails. Here are some tricks / snippets I use :

assert_raises takes a string and/or a class

I want to be able to write

one = Project.new('one')
 
projects

I’ve done this a few times, but I think cruisecontrol.rb’s implementation is the most robust :

  def assert_raises(arg1 = nil, arg2 = nil)
    expected_error = arg1.is_a?(Exception) ? arg1 : nil
    expected_class = arg1.is_a?(Class) ? arg1 : nil
    expected_message = arg1.is_a?(String) ? arg1 : arg2
    begin 
      yield
      fail "expected error was not raised"
    rescue Test::Unit::AssertionFailedError
      raise
    rescue => e
      raise if e.message == "expected error was not raised"
      assert_equal(expected_error, e) if expected_error
      assert_equal(expected_class, e.class, "Unexpected error type raised") if expected_class
      assert_equal(expected_message, e.message, "Unexpected error message") if expected_message.is_a? String
      assert_matched(expected_message, e.message, "Unexpected error message") if expected_message.is_a? Regexp
    end
  end

——
h2. assert_equal_sets

In Java, I used to push things into sets and compare them when I didn’t care about order. In ruby, I sometimes use assert_equal_sets. It does a compare of two arrays independent of order. So

  assert_equal_sets [1, 3, 5], [3, 5, 1]   # passes
  assert_equal_sets [2, 3], [3, 4]    # fails

class Array
  def reorder_like!(other)
    tmp = dup
    clear
    other.each {|x| self

——
h2. file_sandbox for testing against the file system

After dragging this code around me for the last 6 or 7 projects I’ve been on, I finally packaged it up as a gem . It lets you write code like :

in_sandbox do |sandbox|
  sandbox.new :file => 'b/a.txt', :with_contents => 'some stuff'
 
  assert_equal 'some_stuff', File.read(sandbox.root + '/b/a.txt')
end

Basically it creates a temporary directory for you to muck about in. After the block is ended (or teardown is called on your test) that directory and everything in it is guaranteed to be cleaned up. It also has a bunch of methods to make file based things easier like creating a file, etc.

Install it with “gem install file_sandbox”