Add initial support for mutating case statements

TODO

@@ -22,3 +22,4 @@
 * Mutations on Rubinius::AST::Self?
 * Support the numerous Rubinius::AST::SendWithArguments mutations.
 * Fix rubinius to allow setting @vcall_style variable in Rubinius::AST::Send nodes.
+* Add mutations on the conditiosn of case statements. (Rubinius::AST::When)

lib/mutant.rb

@@ -56,6 +56,7 @@ require 'mutant/mutator/noop'
 require 'mutant/mutator/call'
 require 'mutant/mutator/call'
 require 'mutant/mutator/if_statement'
+require 'mutant/mutator/receiver_case'
 require 'mutant/loader' 
 require 'mutant/context'
 require 'mutant/context/constant'

lib/mutant/mutator/receiver_case.rb

@@ -0,0 +1,160 @@
+module Mutant
+  class Mutator
+    # Mutator for Rubinius::AST::When nodes
+    class When < Mutator
+
+      handle(Rubinius::AST::When)
+
+    private
+
+      # Emit mutations
+      #
+      # @return [undefined]
+      #
+      # @api private
+      #
+      def dispatch
+        emit_body_mutations
+      end
+
+      # Emit body mutations
+      #
+      # @return [undefined]
+      #
+      # @api private
+      #
+      def emit_body_mutations
+        Mutator.each(node.body) do |mutation|
+          node = dup_node
+          node.body = mutation
+          emit_unsafe(node)
+        end
+      end
+    end
+
+    # Mutator for Rubinius::AST::ReceiverCase nodes
+    class ReceiverCase < Mutator
+
+      handle(Rubinius::AST::ReceiverCase)
+
+    private
+
+      # Emit mutations
+      #
+      # @return [undefined]
+      #
+      # @api private
+      #
+      def dispatch
+        emit_receiver_mutations
+        emit_when_branch_presence_mutations
+        emit_else_branch_presence_mutation
+        emit_when_branch_mutations
+      end
+
+      # Emit receiver mutation
+      #
+      # @return [undefined]
+      #
+      # @api private
+      #
+      def emit_receiver_mutations
+        Mutator.each(receiver) do |mutant|
+          emit_self(mutant,when_branches,else_branch)
+        end
+      end
+
+      # Emit else branch presence mutation
+      #
+      # @return [undefined]
+      #
+      # @api private
+      #
+      def emit_else_branch_presence_mutation
+        emit_self(receiver,when_branches,nil)
+      end
+
+      # Emit when branch body mutations
+      #
+      # @return [undefined]
+      #
+      # @api private
+      #
+      def emit_when_branch_mutations
+        when_branches.each_with_index do |branch,index|
+          Mutator.each(branch) do |mutant|
+            branches = dup_when_branches
+            branches[index]=mutant
+            emit_self(receiver,branches,else_branch)
+          end
+        end
+      end
+
+      # Emit when branch presence mutations
+      #
+      # @return [undefined]
+      #
+      # @api private
+      #
+      def emit_when_branch_presence_mutations
+        return if one?
+        when_branches.each_index do |index|
+          dup_branches = dup_when_branches
+          dup_branches.delete_at(index)
+          emit_self(receiver,dup_branches,else_branch)
+        end
+      end
+
+      # Check for case there is only one when branch
+      #
+      # @return [true]
+      #   returns true when there is only one when branch
+      #
+      # @api private
+      #
+      def one?
+        when_branches.size == 1
+      end
+
+      # Return duplicatedd when branches
+      #
+      # @return [Array]
+      #
+      # @api private
+      #
+      def dup_when_branches
+        when_branches.dup
+      end
+
+      # Return when branches
+      #
+      # @return [Array]
+      #
+      # @api private
+      #
+      def when_branches
+        node.whens
+      end
+
+      # Return receiver
+      #
+      # @return [Rubinius::AST::Node]
+      #
+      # @api private
+      #
+      def receiver
+        node.receiver
+      end
+
+      # Return else branch
+      #
+      # @return [Rubinius::AST::Node]
+      #
+      # @api private
+      #
+      def else_branch
+        node.else
+      end
+    end
+  end
+end

spec/unit/mutant/mutator/each_spec.rb

@@ -5,6 +5,31 @@
 require 'spec_helper'
 
 describe Mutant::Mutator, '.each' do
+  context 'case statements' do
+    let(:source) { 'case self.condition; when true; true; when false; false; else raise; end' }
+
+    let(:mutations) do
+      mutations = []
+
+      # Delete each when once
+      mutations << 'case self.condition; when true; true; else raise; end'
+      mutations << 'case self.condition; when false; false; else raise; end'
+
+      # Mutate receiver
+      mutations << 'case condition; when true; true; when false; false; else raise; end'
+
+      # Remove else branch
+      mutations << 'case self.condition; when true; true; when false; false; end'
+
+      # Mutate when branch bodies
+      mutations << 'case self.condition; when true; nil;   when false; false; else raise; end'
+      mutations << 'case self.condition; when true; false; when false; false; else raise; end'
+      mutations << 'case self.condition; when true; true;  when false; nil;   else raise; end'
+      mutations << 'case self.condition; when true; true;  when false; true;  else raise; end'
+    end
+
+    it_should_behave_like 'a mutator'
+  end
   pending 'interpolated string literal (DynamicString)' do
     let(:source) { '"foo#{1}bar"' }