method

stub_chain

1.3.0 - Show latest stable - Class: Spec::Mocks::Methods

stub_chain(*methods)

public

Supports stubbing a chain of methods. Each argument represents a method name to stub, and each one returns a proxy object that can accept more stubs, until the last, which returns whatever is passed to +and_return_.

Examples

  # with this in an example ...
  article = double('article')
  Article.stub_chain(:authored_by, :published, :recent).and_return([article])
  # then this will return an Array with the article double in it:
  Article.authored_by(params[:author_id]).published.recent

# File lib/spec/mocks/methods.rb, line 43
      def stub_chain(*methods)
        if methods.length > 1
          if matching_stub = __mock_proxy.find_matching_method_stub(methods[0])
            methods.shift
            matching_stub.invoke_return_block.stub_chain(*methods)
          else
            next_in_chain = Object.new
            stub!(methods.shift) {next_in_chain}
            next_in_chain.stub_chain(*methods)
          end
        else
          stub!(methods.shift)
        end
      end

3Notes

stub_chain is very useful when testing controller code

hosiawak · Mar 4, 20105 thanks

or any other chained method call type that you'd like to stub, example:

in your controller:

def new @user = current_site.users.new end

in your spec:

it "#new should assign a @user" do u = mock("User") controller.stub_chain(:current_site, :users, :new).and_return(u) assigns[:user].should == u end

whereas before you had to stub each chained method call separately:

it "#new should assign a @user" do u = mock("User") users = mock("Users collection", :new => u) site = mock("Site", :users => users) controller.stub!(:current_site).and_return(site) assigns[:user].should == u end

Please note that stub_chain was added to RSpec in version 1.2.6

Works only inside the "it" block

plugawy · Jul 21, 20102 thanks

Please note that +stub_chain+ doesn't work outside of the +it...do...end+ block.

If you need to create more complicated chains using a function you need to use the old way.

correct, but ..

aghyad · Jul 12, 20131 thank

stub_chain provides a very good replacement of long lines of nested stubs, but never forget it violates Law of Demeter; i.e. it indicates an increase of coupling in your classes and this is a bad thing because it means your objects now are making more unnecessary calls to other objects. for example:

def initialize(some_obj)
@obj = some_obj
end

def foo
@obj.x  # GOOD coupling - according to LoD you are allowed to call a method on your object
end

def bar
@obj.x.y   # BAD coupling - can not call a method on a returned value of another method call even if the initial call is legal
end

How is this related to TDD and stubs?

method foo test will have only one stub for a double of some_obj type
method bar will have 2 stubs: the first is going to swallow the other one to produce the result (and then can be shortened using this stub_chain technique)

Always remember: if your tests are using stub_chains --> your code is smelly and possibly tightly coupled.