Add explicit mutator for and_asgn

lib/mutant.rb

@@ -59,6 +59,7 @@ require 'mutant/mutator/node/literal/array'
 require 'mutant/mutator/node/literal/hash'
 require 'mutant/mutator/node/literal/regex'
 require 'mutant/mutator/node/literal/nil'
+require 'mutant/mutator/node/and_asgn'
 require 'mutant/mutator/node/argument'
 require 'mutant/mutator/node/arguments'
 require 'mutant/mutator/node/begin'

lib/mutant/mutator/node/and_asgn.rb

@@ -0,0 +1,30 @@
+# encoding: utf-8
+
+module Mutant
+  class Mutator
+    class Node
+
+      # AndAsgn mutator
+      class AndAsgn < Generic
+
+        handle(:and_asgn)
+
+        children :left, :right
+
+      private
+
+        # Emit mutations
+        #
+        # @return [undefined]
+        #
+        # @api private
+        #
+        def dispatch
+          super
+          emit_nil
+        end
+
+      end # AndAsgn
+    end # Node
+  end # Mutator
+end # Mutant

lib/mutant/mutator/node/generic.rb

@@ -12,7 +12,7 @@ module Mutant
         handle(
           :next, :break, :ensure,
           :dsym, :yield, :rescue, :redo, :defined?,
-          :blockarg, :and_asgn,
+          :blockarg,
           :regopt, :restarg, :resbody, :retry, :arg_expr,
           :kwrestarg, :kwoptarg, :kwarg, :undef, :module, :empty,
           :alias, :for, :xstr, :back_ref, :class,

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

@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-describe Mutant::Mutator::Node::Generic, 'and_asgn' do
+describe Mutant::Mutator::Node::AndAsgn, 'and_asgn' do
   let(:random_fixnum) { 5        }
   let(:random_string) { 'random' }
 
@@ -16,6 +16,7 @@ describe Mutant::Mutator::Node::Generic, 'and_asgn' do
     mutations << 'a &&= -1'
     mutations << 'a &&= 2'
     mutations << 'a &&= 5'
+    mutations << 'nil'
   end
 
   before do