Stubbing Kernel.` (backquote)

Testing RSpec
1

I’m trying to stub(!) the Kernel.` (backquote) method and I’m having
confusing (to me) results. Here’s the method I’m spec’ing:

class Barcode
…
def raw_barcodes
self.make_temporary_copy
OcrBarcode #{self.temp_file_path}
end
…
end

And this is my (newbish) attempt at the spec:

describe “Calling @barcode.raw_barcodes” do
before(:each) do
File.stub!(:exist?).and_return(true)
@barcode = Barcode.new(‘path/to/valid.pdf’)
Kernel.stub!(’`’.to_sym)
end
it “should make a copy of the file” do
@barcode.should_receive(:make_temporary_copy)
@barcode.raw_barcodes
end
it “should make a system call to OcrBarcode”
it “should make the system call to OcrBarcode passing in the
temporary copy of the file”
it “should create foo.pdf.barcode”
end

When I run this (using cmd-d in the TM bundle), the test passes, but I
get this line injected about the green “should make a copy of the
file”:

/Users/george/work/simplify_md/vendor/plugins/rspec/lib/spec/mocks/proxy.rb:129:
command not found: OcrBarcode
/Users/george/work/simplify_md/tmp/valid_2007_10_24_111354_EDT.pdf

(all one line)

Significantly, if I remove the stub (Kernel.stub!(’`’.to_sym)), I get
the same result: passing with the same “command not found” message.

Is there an accepted way to stub subshell calls?

Thanks,

/g

–

George A.

BenevolentCode LLC
O: (410) 461-7553
C: (410) 218-5185

[email protected]

2

I found an alternate route, which may or may not work for others.

Instead of using Kernel#` (backquote / backtick), you might be able to
use Kernel#system. The difference:

Kernel#` returns the standard output of running the command in a
subshell

Kernel#system returns true if the command was found and executed
successfully, otherwise false.

So, in my case, I used:

class Barcode
…
def raw_barcodes
self.make_temporary_copy
system(“OcrBarcode #{self.temp_file_path}”)
…
end
…
end

describe “Calling @barcode.raw_barcodes” do
before(:each) do
File.stub!(:exist?).and_return(true)
@barcode = Barcode.new(‘path/to/valid.pdf’)
Kernel.stub!(:system).and_return(true)
FileUtils.stub!(:cp)
end
it “should make a copy of the file” do
@barcode.should_receive(:make_temporary_copy)
@barcode.raw_barcodes
end
…
end

Note, my spec has changed a bit since my original post, but the gist
remains.

I hope this helps someone down the line.

If you have a better way of spec’ing calls to a subshell, I’d live to
hear it.

/g
On 10/24/07, George A. [email protected] wrote:

end
@barcode.should_receive(:make_temporary_copy)
file":

BenevolentCode LLC
O: (410) 461-7553
C: (410) 218-5185

[email protected]

–

George A.

BenevolentCode LLC
O: (410) 461-7553
C: (410) 218-5185

[email protected]