Do not present un idempotent interface on abstract class

lib/mutant.rb

@@ -61,7 +61,7 @@ module Mutant
 
     begin
       data = Marshal.load(reader.read)
-    rescue ArgumentError => exception
+    rescue ArgumentError
       raise IsolationError, 'Childprocess wrote unmarshallable data'
     end
 

lib/mutant/mutation.rb

@@ -57,8 +57,9 @@ module Mutant
     # @api private
     #
     def identification
-      "#{subject.identification}:#{code}"
+      "#{self.class::SYMBOL}:#{subject.identification}:#{code}"
     end
+    memoize :identification
 
     # Return mutation code
     #

lib/mutant/mutation/evil.rb

@@ -6,17 +6,7 @@ module Mutant
     class Evil < self
 
       SHOULD_FAIL = true
-
-      # Return identification
-      #
-      # @return [String]
-      #
-      # @api private
-      #
-      def identification
-        "evil:#{super}"
-      end
-      memoize :identification
+      SYMBOL      = 'evil'.freeze
 
       # Test if killer is successful
       #

lib/mutant/mutation/neutral.rb

@@ -15,17 +15,6 @@ module Mutant
 
       end # Noop
 
-      # Return identification
-      #
-      # @return [String]
-      #
-      # @api private
-      #
-      def identification
-        "#{self.class::SYMBOL}:#{super}"
-      end
-      memoize :identification
-
     end # Neutral
   end # Mutation
 end # Mutant

spec/unit/mutant/mutation_spec.rb

@@ -4,8 +4,11 @@ require 'spec_helper'
 
 describe Mutant::Mutation do
 
-  let(:class_under_test) { Class.new(described_class) { memoize :identification }             }
-  let(:object)           { class_under_test.new(mutation_subject, Mutant::NodeHelpers::N_NIL) }
+  class TestMutation < Mutant::Mutation
+    SYMBOL = 'test'
+  end
+
+  let(:object)           { TestMutation.new(mutation_subject, Mutant::NodeHelpers::N_NIL)   }
   let(:mutation_subject) { double('Subject', identification: 'subject', source: 'original') }
   let(:node)             { double('Node')                                                   }
 
@@ -37,7 +40,7 @@ describe Mutant::Mutation do
 
     subject { object.identification }
 
-    it { should eql('subject:8771a') }
+    it { should eql('test:subject:8771a') }
 
     it_should_behave_like 'an idempotent method'
   end