Add mutator for kwbegin nodes

lib/mutant.rb

@@ -69,6 +69,7 @@ require 'mutant/mutator/node/connective/binary'
 require 'mutant/mutator/node/const'
 require 'mutant/mutator/node/dstr'
 require 'mutant/mutator/node/dsym'
+require 'mutant/mutator/node/kwbegin'
 require 'mutant/mutator/node/named_value/access'
 require 'mutant/mutator/node/named_value/constant_assignment'
 require 'mutant/mutator/node/named_value/variable_assignment'

lib/mutant/mutator/node/generic.rb

@@ -15,7 +15,7 @@ module Mutant
           :regopt, :resbody, :retry, :arg_expr,
           :kwrestarg, :kwoptarg, :kwarg, :undef, :module, :empty,
           :alias, :for, :xstr, :back_ref, :class,
-          :sclass, :match_with_lvasgn, :match_current_line, :kwbegin
+          :sclass, :match_with_lvasgn, :match_current_line
         )
 
       private

lib/mutant/mutator/node/kwbegin.rb

@@ -0,0 +1,28 @@
+# encoding: utf-8
+
+module Mutant
+  class Mutator
+    class Node
+
+      # Kwbegin mutator
+      class Kwbegin < Generic
+
+        handle(:kwbegin)
+
+      private
+
+        # Emit mutations
+        #
+        # @return [undefined]
+        #
+        # @api private
+        #
+        def dispatch
+          super
+          emit_nil
+        end
+
+      end # Kwbegin
+    end # Node
+  end # Mutator
+end # Mutant

spec/unit/mutant/mutator/node/ensure/mutation_spec.rb

@@ -3,12 +3,13 @@
 require 'spec_helper'
 
 describe Mutant::Mutator::Node::Generic, 'ensure' do
-  let(:source)    { 'begin; rescue; ensure; true; end' }
+  let(:source) { 'begin; rescue; ensure; true; end' }
 
   let(:mutations) do
     mutations = []
     mutations << 'begin; rescue; ensure; false; end'
     mutations << 'begin; rescue; ensure; nil; end'
+    mutations << 'nil'
   end
 
   it_should_behave_like 'a mutator'

spec/unit/mutant/mutator/node/kwbegin/mutation_spec.rb

@@ -0,0 +1,16 @@
+# encoding: utf-8
+
+require 'spec_helper'
+
+describe Mutant::Mutator::Node::Kwbegin, 'kwbegin' do
+  let(:source) { 'begin; true; end' }
+
+  let(:mutations) do
+    mutations = []
+    mutations << 'begin; false; end'
+    mutations << 'begin; nil; end'
+    mutations << 'nil'
+  end
+
+  it_should_behave_like 'a mutator'
+end