We'll create a controller called Sandbox, and write some specs, including stubs for instance methods and filters. Let's begin.

Basic Test Rig

Create a file /spec/controllers/sandbox_controller_spec.rb, with

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

describe SandboxController, " handling someaction" do  
  it "should get real value 10" do

    get :someaction

    assigns[:value].should equal(10)

  end

Then create a file /app/controllers/sandbox_controller.rb, with

class SandboxController < ApplicationController

  def someaction
    @value = somemethod

  end

  protected
  
  def somemethod
    return 10
  end

end

And give it a run,

$ script/spec spec/controllers/sandbox_controller_spec.rb --color --format specdoc

SandboxController handling someaction

- should get real value 10

Finished in 0.134328 seconds

1 example, 0 failures

Stub the Method

Now we'll stub the somemethod. In the spec file add

  it "should get stubbed value 99" do

    controller.stub!(:somemethod).and_return(99)

    get :someaction

    assigns[:value].should equal(99)

  end

and run again,

SandboxController handling someaction
- should get real value 10
- should get stubbed value 99

Alternatively, you could mock it and be more specific, such as

    #controller.stub!(:somemethod).and_return(99)

    controller.should_receive(:somemethod).and_return(99)

Spec a Filter

Next we'll setup a little filter in the controller. Add this spec,

describe SandboxController, " handling filteredaction" do  

  it "should be filtered" do

    get :filteredaction

    assigns[:value].should be_nil

  end

Create the Filter

Add to the controller,

  before_filter :myfilter, :only => :filteredaction

  def filteredaction

    @value = 123

  end

and in the protected section,

  def myfilter

    false

  end

And give it a run,

SandboxController handling filteredaction

- should be filtered

Stub the Filter

Add this to the spec,

  it "should get unfiltered 123" do
    controller.stub!(:myfilter).and_return(true)
    get :filteredaction
    assigns[:value].should equal(123)
  end

and give this one a run,

SandboxController handling filteredaction
- should be filtered
- should get unfiltered 123

Again, alternatively you could mock it,

    #controller.stub!(:myfilter).and_return(true)
    controller.should_receive(:myfilter).with(:no_args).once.and_return(true) 

There you go :)

And this should still work if you move the protected methods out of the controller into, say, ApplicationController class (controllers/application.rb), or into a module in /lib/ that's included in your controller class(es).