rspec users - Oct 2007 - Stubbing a Kernel method?

Is it possible to stub a Kernel method? I''m specifically interested in
the ''open'' method to test some code using open-uri.
I''ve tried:

Kernel.should_receive(:open).with(''filename'').and_return(''data'')

However, this doesn''t seem to work. Any suggestions would be
appreciated.


--Paul

On 10/19/07, Paul Dlug <paul.dlug at gmail.com>
wrote:
> Is it possible to stub a Kernel method? I''m specifically
interested in
> the ''open'' method to test some code using open-uri.
I''ve tried:
>
>
Kernel.should_receive(:open).with(''filename'').and_return(''data'')
>
> However, this doesn''t seem to work. Any suggestions would be
appreciated.
>
>
> --Paul
> _______________________________________________
> rspec-users mailing list
> rspec-users at rubyforge.org
> http://rubyforge.org/mailman/listinfo/rspec-users
>
Kernel gets mixed in to an object, so you need to stub it on the object itself.

describe Newsreader do
  it "should open the uri" do
    @reader = Newsreader.new
    @reader.should_receive(:open_uri).with
"http://example.com/feed.xml"
    @reader.grab_feed "http://example.com/feed.xml"
  end
end

class Newsreader
  def grab_feed(uri)
    response = open_uri uri
  end
end

Pat

On Oct 19, 2007, at 12:18 PM, Paul Dlug wrote:
> Is it possible to stub a Kernel method? I''m specifically
interested in
> the ''open'' method to test some code using open-uri.
I''ve tried:
>
>
Kernel.should_receive(:open).with(''filename'').and_return(''data'')
>
> However, this doesn''t seem to work. Any suggestions would be  
> appreciated.
Use Kernel.stub!.

Another option is to use dependency injection, and pass the mock  
kernel into your class at initialization (something like the following):


class ClassName
   def initialize(arg1, kernel=Kernel)
     @kernel = kernel
   end

   def my_func
     @kernel.open("blah")
     # do something useful here
   end
end

describe ClassName do
   before :each do
     @mock_kernel = mock(Kernel)
     @mock_kernel.stub!(:open).and_return "some text"
   end

   it "should open the file" do
     @obj = ClassName.new("hello", @mock_kernel)

     @mock_kernel.should_receive(:open).with("blah").and_return
"some
text"
     @obj.my_func
   end
end

On Oct 19, 2007, at 5:18 pm, Paul Dlug wrote:
>
Kernel.should_receive(:open).with(''filename'').and_return(''data'')
Had this exact same issue with OpenURI myself two days ago.  The  
other replies are better OO but the quickest way it to use the  
OpenURI.open_uri class method, which you can stub out without  
interfering with Kernel.  (Unless you want it to handle files as well  
as URLs that is.)

BTW I have no idea what the OpenURI.open_uri method is all about, as  
open-uri''s wrapper to Kernel.open does not call it.  But it seems to  
work...

Ashley


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