Can't stub things with Rspec

Question

I have a Rails 4 application, and here is my lib/foobar:

jan@rmbp ~/D/r/v/l/foobar> tree
.
├── foo_bar.rb
└── foobar_spec.rb

0 directories, 2 files

And the files:

foobar_spec.rb

require "spec_helper"

describe "FooBar" do
  subject { FooBar.new }
  its(:foo) { should == "foo"}
  #stubbed version of test crashes
  #FooBar.stub(:foo).and_return("bar")
  #subject { FooBar.new }
  #its(:foo) { should == "bar"}

end

foo_bar.rb

class FooBar
  def foo
    "foo"
  end
end

spec_helper.rb:

# This file is copied to spec/ when you run 'rails generate rspec:install'
ENV["RAILS_ENV"] ||= 'test'
require File.expand_path("../../config/environment", __FILE__)
require 'rspec/rails'
# commented for zeus two runs bug
require 'rspec/autorun'
require 'capybara/rspec'

# Requires supporting ruby files with custom matchers and macros, etc,
# in spec/support/ and its subdirectories.
Dir[Rails.root.join("spec/support/**/*.rb")].each { |f| require f }

# Checks for pending migrations before tests are run.
# If you are not using ActiveRecord, you can remove this line.
ActiveRecord::Migration.check_pending! if defined?(ActiveRecord::Migration)

RSpec.configure do |config|

  config.include Devise::TestHelpers, :type => :controller
  config.include Features::SessionHelpers, type: :feature

  # ## Mock Framework
  #
  # If you prefer to use mocha, flexmock or RR, uncomment the appropriate line:
  #
  # config.mock_with :mocha
  # config.mock_with :flexmock
  # config.mock_with :rr
  config.mock_with :rspec

  # If you're not using ActiveRecord, or you'd prefer not to run each of your
  # examples within a transaction, remove the following line or assign false
  # instead of true.
  config.use_transactional_fixtures = false

  config.before(:suite) do
    DatabaseCleaner.strategy = :truncation
  end

  config.before(:each) do
    DatabaseCleaner.start
  end

  config.after(:each) do
    DatabaseCleaner.clean
  end

  # If true, the base class of anonymous controllers will be inferred
  # automatically. This will be the default behavior in future versions of
  # rspec-rails.
  config.infer_base_class_for_anonymous_controllers = false

  # Run specs in random order to surface order dependencies. If you find an
  # order dependency and want to debug it, you can fix the order by providing
  # the seed, which is printed after each run.
  #     --seed 1234
  config.order = "random"
end

The spec passes fine. But when I uncomment this line:

# FooBar.stub(:foo).and_return("bar")

It fails with:

/Users/jan/.rvm/gems/ruby-2.0.0-p247/gems/rspec-mocks-2.14.3/lib/rspec/mocks.rb:26:in `proxy_for': undefined method `proxy_for' for nil:NilClass (NoMethodError)

What is wrong?

EDIT: Also, I can't seem to be able to use webmock either.

  stub_request(:post, "https://accounts.google.com/o/oauth2/token")
         .with(:body => { "client_id"     => CLIENT_ID,
                         "client_secret" => CLIENT_SECRET,
                         "refresh_token" => refresh_token, }
         ).to_return(:status => 200,
                     :body => File.read("#{$fixtures}/refresh_token.json"))

Returns:

/Users/jan/Documents/ruby/vince.re/lib/youtube/you_tube_test.rb:9:in block in <top (required)>': undefined methodstub_request' for < Class :0x007f8159bbe7c0> (NoMethodError)

SOLUTION: Thanks to @gotva for telling me about stubs requirement to reside within it blocks. Here is my new, fixed webmock test, and it works great:

  context "when token is nil it" do
    it "called refresh method" do
      YouTube.any_instance.should_receive(:refresh_auth_token).with(data["refresh"]) 
      YouTube.new(data["uid"], nil, data["refresh"])
    end
    it "refreshed the authentation token" do
      stub_request(:post, "https://accounts.google.com/o/oauth2/token")
            .with(:body => { "client_id"     => CLIENT_ID,
                        "client_secret" => CLIENT_SECRET,
                        "grant_type"=>"refresh_token",
                        "refresh_token" => data["refresh"], }
            ).to_return(:status => 200,
                        :body => File.read("#{$fixtures}/refresh_token.json"))
        yt = YouTube.new(data["uid"], nil, data["refresh"])
        yt.token.should == data["access_token"]
    end
  end

Answer 1

It seems to me that using this stub

FooBar.stub(:foo).and_return("bar")

you are trying to stub nonexistent method. Method foo is instance method but you stub class method.

If you would like to stub instance method FooBar#foo use any_instance

FooBar.any_instance.stub(:foo).and_return("bar")

Update from comments

Apply stub in it or before blocks.

new variant:

it 'place here some description for method foo' do
  FooBar.any_instance.stub(:foo).and_return("bar") 
  expect(FooBar.new.foo).to eql('bar')
end 

or

# the order is important! 
describe "FooBar" do 
  before { FooBar.any_instance.stub(:foo).and_return("bar") } 
  subject { FooBar.new } 
  its(:foo) { should == "foo"} 
end