Unable to stub helper method with rspec

问题

I am trying to stub a method on a helper that is defined in my controller. For example:

class ApplicationController < ActionController::Base
  def current_user
    @current_user ||= authenticated_user_method
  end
  helper_method :current_user
end

module SomeHelper
  def do_something
    current_user.call_a_method
  end
end

In my Rspec:

describe SomeHelper
  it "why cant i stub a helper method?!" do
    helper.stub!(:current_user).and_return(@user)
    helper.respond_to?(:current_user).should be_true # Fails
    helper.do_something # Fails 'no method current_user'
  end
end

In spec/support/authentication.rb

module RspecAuthentication
  def sign_in(user)
    controller.stub!(:current_user).and_return(user)
    controller.stub!(:authenticate!).and_return(true)

    helper.stub(:current_user).and_return(user) if respond_to?(:helper)
  end
end

RSpec.configure do |config|
  config.include RspecAuthentication, :type => :controller
  config.include RspecAuthentication, :type => :view
  config.include RspecAuthentication, :type => :helper
end

I asked a similar question here, but settled on a work around. This strange behavior has creeped up again and I would like to understand why this doesnt work.

UPDATE: I have found that calling controller.stub!(:current_user).and_return(@user) before helper.stub!(...) is what is causing this behavior. This is easy enough to fix in spec/support/authentication.rb, but is this a bug in Rspec? I dont see why it would be expected to not be able to stub a method on a helper if it was already stubbed on a controller.

回答1:

Try this, it worked for me:

describe SomeHelper
  before :each do
    @helper = Object.new.extend SomeHelper
  end

  it "why cant i stub a helper method?!" do
    @helper.stub!(:current_user).and_return(@user)
    # ...
  end
end

The first part is based on this reply by the author of RSpec, and the second part is based on this Stack Overflow answer.

回答2:

Update to Matthew Ratzloff's answer: You don't need the instance object and stub! has been deprecated

it "why can't I stub a helper method?!" do
  helper.stub(:current_user) { user }
  expect(helper.do_something).to eq 'something'
end

Edit. The RSpec 3 way to stub! would be:

allow(helper).to receive(:current_user) { user }

See: https://relishapp.com/rspec/rspec-mocks/v/3-2/docs/

回答3:

In RSpec 3.5 RSpec, it seems like helper is no longer accessible from an it block. (It will give you the following message:

helper is not available from within an example (e.g. an it block) or from constructs that run in the scope of an example (e.g. before, let, etc). It is only available on an example group (e.g. a describe or context block).

(I can't seem to find any documentation on this change, this is all knowledge gained experimentally).

The key to solving this is knowing that helper methods are instance methods, and that for your own helper methods it's easy to do this:

allow_any_instance_of( SomeHelper ).to receive(:current_user).and_return(user) 

This is what finally worked for me

Footnotes/Credit Where Credit Due:

• Super Props to a blog entry by Johnny Ji about their struggles stubbing helper/instance methods

回答4:

Rspec 3

  user = double(image: urlurl)
  allow(helper).to receive(:current_user).and_return(user)
  expect(helper.get_user_header).to eq("/uploads/user/1/logo.png")

回答5:

This worked for me in the case of RSpec 3:

let(:user) { create :user }
helper do
  def current_user; end
end
before do
  allow(helper).to receive(:current_user).and_return user
end

来源：https://stackoverflow.com/questions/10537932/unable-to-stub-helper-method-with-rspec