Regression testing: cairo mock object stores graphics calls

So the idea behind this is maintain an "expected value" for the sample runs. We store the graphics calls and their arguments as a readable text file. Any change in the samples will break this, but the idea is to make sure this doesn't get broken unexpectedly.

Rearranged the data files in specs

spec/samples/samples_regression_spec.rb

@@ -0,0 +1,44 @@
+require 'spec_helper'
+require 'squib'
+require 'pp'
+require 'method_log_proxy'
+
+
+describe Squib do
+
+  context 'samples' do
+    it 'should execute with no errors' do
+      allow(ProgressBar).to receive(:create).and_return(Squib::DoNothing.new)
+      samples = File.expand_path('../../samples', File.dirname(__FILE__))
+      Dir["#{samples}/**/*.rb"].each do |sample|
+        Dir.chdir(samples) do #to save to _output
+          load sample
+        end
+      end
+    end
+
+    it 'did not change against regression logs' do
+      samples = File.expand_path('../../samples', File.dirname(__FILE__))
+      Dir["#{samples}/**/*.rb"].each do |sample|
+        sample_name = File.basename(sample)
+        header = "=== #{sample_name} ===\n"
+        Dir.chdir(samples) do #to save to _output
+          strio = StringIO.new
+          strio << header
+          mock_cairo(strio)
+          load sample
+          test_file_str = ""
+          # Use this to overwrite the regression with current state
+          # Use ONLY temporarily after you are happy with the new sample log
+          # File.open(sample_regression_file(sample_name), 'w+') do |f|
+          #   f.write(strio.string) # write back out to expected file
+          # end
+          test_file_str << File.open(sample_regression_file(sample_name)).read
+          expect(strio.string).to eq(test_file_str)
+        end
+      end
+    end
+
+  end
+
+end