rspec users - Oct 2008 - Mocking Kernel.system or Kernel.` for external application calls

I''m running into an issue while trying to test the execution of some
external applications called from inside my models.

class OmssaPacker
  def self.run_omssa_aws2ez2_unix(parameters)
    system("perl /pipeline/vipdac/lib/omssa_aws2ez2_unix.pl
#{parameters}")
  end
end

..spec code...
  describe "run omssa aws2ez2 unix" do
    it "should run the perl file" do
     
Kernel.should_receive(:system).with(/omssa_aws2ez2_unix\.pl/).and_return(true)
      OmssaPacker.run_omssa_aws2ez2_unix("file").should be_true
    end
  end
...spec code...

Returns:
should run the perl file
Mock ''Module'' expected :system with (/omssa_aws2ez2_unix\.pl/)
once,
but received it 0 times

And it also actually attempts to run the perl script, since I can see
the output in the window. If I change the code to:

  def self.run_omssa_aws2ez2_unix(parameters)
    %x{ perl /pipeline/vipdac/lib/omssa_aws2ez2_unix.pl #{parameters} }
  end

...spec code...
  describe "run omssa aws2ez2 unix" do
    it "should run the perl file" do
      Kernel.should_receive(:`).with(/omssa_aws2ez2_unix\.pl/).and_return(true)
      OmssaPacker.run_omssa_aws2ez2_unix("file").should be_true
    end
  end
...spec code...

Returns:
should run the perl file
expected true, got ""Program:  omssa_aws2ez2.pl  ...output from perl
program about command line options..."

It seems that the attempts to mock Kernel are being ignored and it''s
just running the scripts anyway. I''m guessing that I''m setting
up the
mock incorrectly, but I''m not sure how.

I''ve also tried Kernel.stub!(:system).and_return(true) with the same
results.

"Joey Geiger" <jgeiger at gmail.com> writes:
> I''m running into an issue while trying to test the execution of
some
> external applications called from inside my models.
>
> class OmssaPacker
>   def self.run_omssa_aws2ez2_unix(parameters)
>     system("perl /pipeline/vipdac/lib/omssa_aws2ez2_unix.pl
#{parameters}")
>   end
> end
>
> ..spec code...
>   describe "run omssa aws2ez2 unix" do
>     it "should run the perl file" do
>      
Kernel.should_receive(:system).with(/omssa_aws2ez2_unix\.pl/).and_return(true)
>       OmssaPacker.run_omssa_aws2ez2_unix("file").should be_true
>     end
>   end
> ...spec code...
>
> Returns:
> should run the perl file
> Mock ''Module'' expected :system with
(/omssa_aws2ez2_unix\.pl/) once,
> but received it 0 times
>
> And it also actually attempts to run the perl script, since I can see
> the output in the window. If I change the code to:
>
>   def self.run_omssa_aws2ez2_unix(parameters)
>     %x{ perl /pipeline/vipdac/lib/omssa_aws2ez2_unix.pl #{parameters} }
>   end
>
> ...spec code...
>   describe "run omssa aws2ez2 unix" do
>     it "should run the perl file" do
>      
Kernel.should_receive(:`).with(/omssa_aws2ez2_unix\.pl/).and_return(true)
>       OmssaPacker.run_omssa_aws2ez2_unix("file").should be_true
>     end
>   end
> ...spec code...
>
> Returns:
> should run the perl file
> expected true, got ""Program:  omssa_aws2ez2.pl  ...output from
perl
> program about command line options..."
>
> It seems that the attempts to mock Kernel are being ignored and
it''s
> just running the scripts anyway. I''m guessing that I''m
setting up the
> mock incorrectly, but I''m not sure how.
>
> I''ve also tried Kernel.stub!(:system).and_return(true) with the
same results.
> _______________________________________________
> rspec-users mailing list
> rspec-users at rubyforge.org
> http://rubyforge.org/mailman/listinfo/rspec-users
Hi Joey,

In Ruby, any time you send a message without an explicit receiver, the
message has an implicit receiver of ''self''.  So from this we
can infer
that you don''t want to stub Kernel#system, but rather
OmssaPacker.system.  The other side of the coin for understanding this
is that while the method is defined in Kernel, it''s not defined ON
Kernel.  Kernel is a module that''s mixed into Object, so its methods
are
defined on all Objects.

Kernel.should_receive(:system).with(/omssa_aws2ez2_unix\.pl/).and_return(true)
is what you''re looking for.

Pat

>
Kernel.should_receive(:system).with(/omssa_aws2ez2_unix\.pl/).and_return(true)
> is what you''re looking for.
erm, that''s a tad embarrasing :)  I copy/pasted your line without
editing it!  It should be:
OmssaPacker.should_receive(:system).with(/omssa_aws2ez2_unix\.pl/).and_return(true)

Pat

Thank you, it''s now working as expected.

I was basing the code on what I had seen before, with examples of
people stubbing Kernel.system, so I wasn''t thinking about just using
the object itself.