Tip #26 - Start Small

Tue Jun 24 07:22:38 -0700 2008

If you are getting frustrated with RSpec, then you have probably skipped a gradient. Start smaller!

When I was trying to teach a co-worker how to write specs, I ran into a gradient problem. He was trying to write specs for an existing app and controller setup that had the usual create action in the controller, it also had a before filter checking logins and timezones, the controller action was simple enough, something like this:

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def create
  @person = Person.new(params[:person])

  respond_to do |format|
    if @person.save
      flash[:notice] = 'Person was successfully created.'
      format.html { redirect_to(@person) }
      format.js
    else
      format.html { render :action => "new" }
      format.js
    end
  end
end

Now, if you are really starting out, don’t start with this. Start with something MUCH simpler… maybe like this:

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def new
end

That would be a good gradient :)

No, seriously, if you just “don’t get RSpec”, then you skipped a gradient or went past something you don’t understand. Go back to an earlier gradient and come forward again.

I can say without a doubt that the #1 problem that new RSpec users have is code that tries to do too much.

Let the code evolve step by step from NOTHING and then come forward, the RSpec webpage has it right when it says “take very small steps”.

The skipped gradient problem is hard enough for experienced RSpec coders trying to fix an existing broken spec, but for someone who hasn’t understood the basics of how RSpec works, it is simply a killer. You don’t want to be wondering if your use of response.should have_tag(‘div’, 2) is correct when all the specs are not working and you have red failing tests everywhere… “Thar b’ dragn’s thar matey!”

If you run into this problem, then go make a new scratch app and start specing it from the ground up, with minimal code generation.

Something like this:

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baci:test mikel$ ./script/generate rspec_controller welcome 
      exists  app/controllers/
      exists  app/helpers/
      create  app/views/welcome
      exists  spec/controllers/
      exists  spec/helpers/
      create  spec/views/welcome
      create  spec/controllers/welcome_controller_spec.rb
      create  spec/helpers/welcome_helper_spec.rb
      create  app/controllers/welcome_controller.rb
      create  app/helpers/welcome_helper.rb

Now go into the spec/controllers/welcome_controller_spec.rb and check it out:

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require File.expand_path(File.dirname(__FILE__) + '/../spec_helper')

describe WelcomeController do

  #Delete this example and add some real ones
  it "should use WelcomeController" do
    controller.should be_an_instance_of(WelcomeController)
  end

end

Your standard RSpec template. This is good enough to start. We are going to build a welcome page here, so lets write our first spec:

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describe "getting the home page of the site" do
  it "should be a success" do
    get :index
    response.should be_success
  end
end

And stop RIGHT THERE and run your specs, it will fail because no index action or template exists yet. Once it has failed, do the next smallest thing that could possibly pass. Write an empty index action:

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class WelcomeController < ApplicationController
  def index
  end
end

And then run your specs, it will now pass. Good! Now you can start building on that stable datum of ‘it is passing now, if I add this one thing it should fail, then if I code this one thing, then it will pass again.’

While I am at it, ban the script/generate rspec_scaffold command from your development vocabulary until you know how to do every step in the code that the scaffold generates (and even then, the use is questionable). The great thing that the scaffold does is provide examples. If you are new to RSpec, you might be tempted to use the scaffold, I would recommend instead to make a scratch up, and use the scaffold there, and then use the code examples step by step in your own app building up your own specs.

This will give you a much broader understanding of how RSpec works.

Trying to spec some huge pre-existing code block as your introduction to RSpec is not impossible, but it is a pretty steep gradient and will result in more hair loss than passing specs.

blogLater

Mikel

  1. jonathan Says:
    Fri Jun 27 01:36:21 -0700 2008

    Thanks, Mikel. I’ll try to give it a go again as I did try rspec on an existing app w/over 100 models. I did not have much success and resorted back to Test::Unit.

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