Proposal: Inform user when testing a private method

Gemfile

@@ -29,3 +29,5 @@ gem 'contracts', '< 0.16' if RUBY_VERSION < '1.9.0'
 gem 'coveralls', :require => false, :platform => :mri_20
 
 eval File.read('Gemfile-custom') if File.exist?('Gemfile-custom')
+
+gem 'pry'

features/its.feature

@@ -61,7 +61,7 @@ Feature: attribute of subject
       Person
         with one phone number (555-1212)
           phone_numbers.first
-            is expected to eq "555-1212"
+            should eq "555-1212"
       """
 
   Scenario: specify value of an attribute of a hash

lib/rspec/its.rb

@@ -95,7 +95,7 @@ module Its
     #
     #   # This ...
     #   describe Array do
-    #     its(:size, :focus) { should eq(0) }
+    #     its(:size, focus: true) { should eq(0) }
     #   end
     #
     #   # ... generates the same runtime structure as this:
@@ -131,7 +131,31 @@ def its(attribute, *options, &block)
           else
             attribute_chain = attribute.to_s.split('.')
             attribute_chain.inject(subject) do |inner_subject, attr|
+
+              # When NilClass:   user didnt set the rspec setting
+              # When FalseClass: skip this block
+              if RSpec.configuration.its_private_method_debug.is_a? NilClass
+
+                # respond_to? only looks in the public method space
+                # TODO Check NoMethodError
+                # TODO Check if inner_subject some kind of const
+                # inner_subject.method_defined?(attr) && !inner_subject.respond_to?(attr)
+                if !inner_subject.respond_to?(attr)
+
+                  if RSpec.configuration.its_private_method_debug
+                    # TODO if debug: show spec:line_num for better indication
+                    puts its_caller.first
+                  end
+
+                  puts "You are testing a private method. Set RSpec its_private_method_debug setting to show more info or hide it completly."
+
+                  # TODO Add deprecation warning to drop private method calling
+                  # for the next major release
+                end
+              end
+
               inner_subject.send(attr)
+
             end
           end
         end
@@ -175,6 +199,11 @@ def should_not(matcher=nil, message=nil)
 end
 
 RSpec.configure do |rspec|
+
+  # Add RSpec configuration setting to allow
+  # the user to handle private method invoking warning
+  rspec.add_setting :its_private_method_debug
+
   rspec.extend RSpec::Its
   rspec.backtrace_exclusion_patterns << %r(/lib/rspec/its)
 end

spec/rspec/its_spec.rb

@@ -9,6 +9,19 @@ module RSpec
           its([]) { expect(described_class).to be Its }
         end
       end
+      context "" do
+        subject do
+          Class.new do
+            private
+
+            def name
+              'Maria'
+            end
+          end.new
+        end
+
+        its(:name, :focus) { should eq('Maria') }
+      end
       context "with explicit subject" do
         subject do
           Class.new do

spec/spec_helper.rb

@@ -12,4 +12,6 @@ def method_missing(method, *args, &block)
 RSpec.configure do |config|
   config.run_all_when_everything_filtered = true
   config.order = 'random'
+
+  # config.its_private_method_debug = true
 end