Testing methods called on yielded object

Question

I have the following controller test case:

def test_showplain
  Cleaner.expect(:parse).with(@somecontent)
  Cleaner.any_instance.stubs(:plainversion).returns(@returnvalue)

  post :showplain, {:content => @somecontent}

end

This works fine, except that I want the "stubs(:plainversion)" to be an "expects(:plainversion)".

Here's the controller code:

def showplain
   Cleaner.parse(params[:content]) do | cleaner |
      @output = cleaner.plainversion
   end
end

And the Cleaner is simply:

class Cleaner

   ### other code and methods ###

   def self.parse(@content) 
     cleaner = Cleaner.new(@content)
     yield cleaner
     cleaner.close
   end

   def plainversion
      ### operate on @content and return ###
   end

end

Again, I can't figure out how to reliably test the "cleaner" that is made available from the "parse" method. Any suggestions?

Answer 1

This is a little tricky. The easiest a approach will be to break the problem into two pieces: the testing of the controller and the testing of the controller.

You have the testing of the controller set-- just remove your expectation around plainversion call.

Then, separately, you want to test the Cleaner.parse method.

cleaner = Cleaner.new('x');
cleaner.expects :close

Cleaner.expects(:new).returns(cleaner)

called_with = nil
Cleaner.parse('test') do |p|
  called_with = p
end
assert_equal p, cleaner

That is not very clear what's going on. Makes me think that there is a simpler version of this. Can cleaner just be a simple function that takes a string and returns another one? Skip all the yielding and variable scoping? That will be much easier to test.