Add fingerprint support

cuke_modeler.gemspec

@@ -44,4 +44,5 @@ Gem::Specification.new do |spec|
   # Coveralls gem does not support any newer version than this
   spec.add_development_dependency 'simplecov', '<= 0.16.1'
   spec.add_development_dependency 'test-unit', '< 4.0.0'
+  spec.add_development_dependency 'pry', '~> 0.13.1'
 end

lib/cuke_modeler.rb

@@ -15,6 +15,7 @@ module CukeModeler
 require 'cuke_modeler/named'
 require 'cuke_modeler/described'
 require 'cuke_modeler/stepped'
+require 'cuke_modeler/fingerprint'
 require 'cuke_modeler/models/model'
 require 'cuke_modeler/models/feature_file'
 require 'cuke_modeler/models/directory'

lib/cuke_modeler/fingerprint.rb

@@ -0,0 +1,33 @@
+require 'digest/md5'
+
+module CukeModeler
+
+  # NOT A PART OF THE PUBLIC API
+  # A mix-in module containing methods used by models that represent an element that has a name.
+
+  module Fingerprint
+
+    # NOTE: create a fingerprint for the given model using Digest::MD5
+    def fingerprint
+      # NOTE: yield the result value of the block as the argument to .hexdigest
+      if block_given?
+        value = yield self
+
+        # NOTE: The block returned nil, nothing to digest here
+        return nil unless value.present?
+
+        @fingerprint = Digest::MD5.hexdigest(value)
+
+        return @fingerprint
+      end
+
+      # NOTE: memoize fingerprint for improved performance
+      @fingerprint ||= begin
+        # NOTE: no block given, .hexdigest the to_s of the model
+        Digest::MD5.hexdigest(to_s)
+      end
+    end
+
+  end
+
+end

lib/cuke_modeler/models/model.rb

@@ -6,6 +6,7 @@ class Model
 
     include Nested
     include Containing
+    include Fingerprint
 
 
     # Creates a new Model object and, if *source_text* is provided,

testing/rspec/spec/integration/fingerprint_integration_spec.rb

@@ -0,0 +1,94 @@
+require "#{File.dirname(__FILE__)}/../spec_helper"
+require 'benchmark'
+
+describe 'Fingerprint, Integration' do
+
+  describe '.fingerprint' do
+
+    let(:model) { CukeModeler::Step.new }
+
+    before do
+      model.keyword = 'Given'
+      model.text = 'I am testing the fingerprint'
+    end
+
+    describe 'getting a fingerprint without args' do
+
+      it 'returns the Digest::MD5 of the to_s representation' do
+        expect(model.fingerprint).to eq(Digest::MD5.hexdigest(model.to_s))
+      end
+
+    end
+
+    describe 'getting a fingerprint with a block' do
+
+      it 'returns the Digest::MD5 of the block return value' do
+        fingerprint = model.fingerprint do |m|
+          m.text
+        end
+
+        expect(fingerprint).to eq(Digest::MD5.hexdigest(model.text))
+      end
+
+    end
+
+    describe 'getting a fingerprint with a block that returns nil' do
+
+      it 'returns nil' do
+        fingerprint = model.fingerprint do |m|
+          nil
+        end
+
+        expect(fingerprint).to eq(nil)
+      end
+
+    end
+
+    describe 'comparing fingerprints' do
+
+      let(:maximum_viable_gherkin) do
+        "@a_tag
+         #{SCENARIO_KEYWORD}: test scenario
+
+         Scenario
+         description
+
+           #{STEP_KEYWORD} a step
+             | value1 |
+             | value2 |
+           #{STEP_KEYWORD} another step
+             \"\"\" with content type
+             some text
+             \"\"\""
+      end
+
+      let(:model_one) { CukeModeler::Scenario.new(maximum_viable_gherkin) }
+      let(:model_two) { CukeModeler::Scenario.new(maximum_viable_gherkin) }
+      let(:model_three) { CukeModeler::Scenario.new }
+
+      it 'should result in the same fingerprint when classes exactly the same' do
+        expect(model_one.fingerprint).to eq(model_two.fingerprint)
+        expect(model_one.fingerprint).not_to eq(model_three.fingerprint)
+      end
+
+      it 'should recalculate the fingerprint when using a block' do
+        model_one_fingerprint = model_one.fingerprint
+        model_one_block_fingerprint = model_one.fingerprint { |m| m.name }
+
+        expect(model_one_fingerprint).not_to eq(model_one_block_fingerprint)
+        expect(model_one.fingerprint).to eq(model_one_block_fingerprint)
+      end
+
+      it 'is more performant than ==' do
+        equals_time = Benchmark.realtime { model_one == model_two }
+        fingerprint_time = Benchmark.realtime { model_one.fingerprint == model_two.fingerprint }
+
+        expect(equals_time > fingerprint_time).to eq(true)
+      end
+
+    end
+
+  end
+
+end
+

testing/rspec/spec/spec_helper.rb

@@ -24,6 +24,8 @@
 require_relative '../../helper_methods'
 
 require 'rubygems/mock_gem_ui'
+require 'digest/md5'
+require 'pry'
 
 
 # Use a random dialect for testing in order to avoid hard coded language assumptions in the

testing/rspec/spec/unit/fingerprint_unit_spec.rb

@@ -0,0 +1,12 @@
+require "#{File.dirname(__FILE__)}/../spec_helper"
+
+describe 'Fingerprint, Unit', unit_test: true do
+
+  let(:nodule) { CukeModeler::Fingerprint }
+  let(:model) { Object.new.extend(nodule) }
+
+
+  it 'has a fingerprint' do
+    expect(model).to respond_to(:fingerprint)
+  end
+end