stack level too deep (SystemStackError) when using both rspec and cucumber with ruby and rails

Question

This is a question about what debugging strategy I should use when encountering a stack level too deep (SystemStackError) using Ruby and Rails.

I am seeing these errors when using either rspec or cucumber

perrys-MacBook-Pro:pc perry_mac$ cucumber
stack level too deep (SystemStackError)
/Users/perry_mac/.rvm/gems/ruby-1.9.3-p327/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:240  

perrys-MacBook-Pro:pc perry_mac$ rspec
/Users/perry_mac/.rvm/gems/ruby-1.9.3-p327/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:240: stack level too deep (SystemStackError)
perrys-MacBook-Pro:pc perry_mac$ 

I suspect the problem I have introduced here is independent of both rspec and cucumber. I'm not sure how to narrow down the problem. What should I try next?

I have already tried bundle update, which ran fine.

The app runs fine under rails s , but I'd like to make use of the rspec and cucumber tests I've written.

ADDENDUM:

I see this with the simplest of tests, for instance:

perrys-MacBook-Pro:pc perry_mac$ cat ./spec/controllers/page_controller_spec.rb
require 'spec_helper'

describe PageController do

end
perrys-MacBook-Pro:pc perry_mac$ rspec ./spec/controllers/page_controller_spec.rb
/Users/perry_mac/.rvm/gems/ruby-1.9.3-p327/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:240: stack level too deep (SystemStackError)
perrys-MacBook-Pro:pc perry_mac$ 

ADDENDUM 2: pastebin of spec_helper is here: http://pastebin.com/ePdGyHQh

ADDENDUM 3: pastebin of Gemfile is here: http://pastebin.com/xkLYGjsY

ADDENDUM 4: I have determined that this is the line in spec_helper.rb that leads to the error

require File.expand_path("../../config/environment", __FILE__)

If I put a deliberate syntax error right before that line, I get a 'syntax error' If I put the same syntax error after the line, I get the 'stack too deep error.'

Seems like some progress. Should require File.expand_path("../../config/environment", __FILE__) be written some other way?

ADDENDUM 5: I added this to spec_helper.rb:

puts File.path("../../config/environment") 
puts __FILE__
require File.expand_path("../../config/environment", __FILE__)

and now see this:

perrys-MacBook-Pro:pc perry_mac$ rspec ./spec/controllers/page_controller_spec.rb
../../config/environment
/Users/perry_mac/rails_projects/pc/spec/spec_helper.rb
/Users/perry_mac/.rvm/gems/ruby-1.9.3-p327/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:240: stack level too deep (SystemStackError)
perrys-MacBook-Pro:pc perry_mac$ 

... but am not sure what the implications are based on the output.

ADDENDUM 6:
Using pry, I stepped through the code. A pastebin of the output just before failure is here: http://pastebin.com/c6ZfPmVn Is this helpful or should I include something else? Looks like execution continues up until this point:

/Users/perry_mac/.rvm/gems/ruby-1.9.3-p327/gems/rspec-core-2.13.1/lib/rspec/core.rb @ line 69 RSpec.reset

ADDENDUM 7: I just confirmed I can checkout an older git branch that has working rspec and cucumber. Could having a working branch help me debug the more recent broken branch in any way?

Addendum 8: According to the Pry execution trace, the error happens immediately after a call to Rspec.reset

Answer 1

I found the cause using

git bisect

and

git show [commitID]

I was able to go back through my log of commits and find a working version. Then, using the instructions for git bisect here, I was able to find the commit that introduced the stack too deep error. I then used git show [commitID] to see two potential lines of code that were to blame. They were:

# file:app/controllers/thisControllerFileIhave.rb

require 'dicom'
include DICOM

making this change seems to have fixed the problem:

require 'dicom'
#include DICOM

Quite honestly, I do not recall why I added 'include DICOM' (commit was in Oct,2012) nor do I understand why or how this would cause both rspec and cucumber to fail so spectacularly and cryptically. Nor do I understand how running the app under rails s works fine with this code, but the test suite does not. I would thank the poster who suggested git bisect, but their comment seems to have been removed.

Most of the answers and comments I got for this question did not directly address a debugging strategy as much as they offered first hand accounts of when the authors had seen and corrected an error like this. I am grateful to have come across git bisect and git show and I feel they are really powerful options for pinpointing the source of problems like this one.