Refactor unit test layout

Set up spec tree like chef, to add room for other tests and make room
for support files.

Also include platform helpers from Chef to use as exclusions.

spec/spec_helper.rb

@@ -1,5 +1,6 @@
 require 'rspec'
-require 'mixlib/config'
+
+require 'spec/support/platform_helpers'
 
 $:.unshift(File.dirname(__FILE__) + '/../lib')
 require 'ohai'
@@ -54,3 +55,14 @@ def from_file(filename)
     self.instance_eval(IO.read(filename), filename, 1)
   end
 end
+
+RSpec.configure do |config|
+  config.treat_symbols_as_metadata_keys_with_true_values = true
+
+  config.filter_run_excluding :windows_only => true unless windows?
+  config.filter_run_excluding :unix_only => true unless unix?
+  config.filter_run_excluding :ruby_18_only => true unless ruby_18?
+  config.filter_run_excluding :ruby_19_only => true unless ruby_19?
+  config.filter_run_excluding :requires_root => true unless ENV['USER'] == 'root'
+  config.filter_run_excluding :requires_unprivileged_user => true if ENV['USER'] == 'root'
+end

spec/support/platform_helpers.rb

@@ -0,0 +1,31 @@
+def ruby_19?
+  !!(RUBY_VERSION =~ /^1.9/)
+end
+
+def ruby_18?
+  !!(RUBY_VERSION =~ /^1.8/)
+end
+
+def windows?
+  !!(RUBY_PLATFORM =~ /mswin|mingw|windows/)
+end
+
+# def jruby?
+
+def unix?
+  !windows?
+end
+
+def os_x?
+  !!(RUBY_PLATFORM =~ /darwin/)
+end
+
+def solaris?
+  !!(RUBY_PLATFORM =~ /solaris/)
+end
+
+def freebsd?
+  !!(RUBY_PLATFORM =~ /freebsd/)
+end
+
+DEV_NULL = windows? ? 'NUL' : '/dev/null'