Add binary connective mutator

lib/mutant.rb

@@ -58,6 +58,7 @@ require 'mutant/mutator/node/argument'
 require 'mutant/mutator/node/arguments'
 require 'mutant/mutator/node/begin'
 require 'mutant/mutator/node/cbase'
+require 'mutant/mutator/node/connective/binary'
 require 'mutant/mutator/node/const'
 require 'mutant/mutator/node/named_value/access'
 require 'mutant/mutator/node/named_value/constant_assignment'

lib/mutant/mutator/node/connective/binary.rb

@@ -0,0 +1,61 @@
+module Mutant
+  class Mutator
+    class Node
+      module Connective
+
+        # Mutation emitter to handle binary connectives
+        class Binary < Node
+
+          INVERSE = {
+            :and => :or,
+            :or  => :and,
+          }.freeze
+
+          handle *INVERSE.keys
+
+          children :left, :right
+
+        private
+
+          # Emit mutations
+          #
+          # @return [undefined]
+          #
+          # @api private
+          #
+          def dispatch
+            emit_nil
+            emit(left)
+            emit(right)
+            mutate_operator
+            mutate_conditions
+          end
+
+          # Emit operator mutations
+          #
+          # @return [undefined]
+          #
+          # @api private
+          #
+          def mutate_operator
+            emit(s(INVERSE.fetch(node.type), left, right))
+          end
+
+          # Emit condition mutations
+          #
+          # @return [undefined]
+          #
+          # @api private
+          #
+          def mutate_conditions
+            [N_TRUE, N_FALSE, N_NIL].each do |condition|
+              emit_left(condition)  unless left == condition
+              emit_right(condition) unless right == condition
+            end
+          end
+
+        end # Binary
+      end # Connective
+    end # Node
+  end # Mutator
+end # Mutant

lib/mutant/mutator/node/generic.rb

@@ -8,7 +8,7 @@ module Mutant
         # These nodes still need a dedicated mutator,
         # your contribution is that close!
         handle(
-          :not, :or, :and, :defined,
+          :not, :defined,
           :next, :break, :match, :ensure,
           :dstr, :dsym, :yield, :rescue, :redo, :defined?,
           :blockarg, :block_pass, :op_asgn, :and_asgn,

spec/unit/mutant/mutator/node/connective/binary/mutation_spec.rb

@@ -0,0 +1,45 @@
+require 'spec_helper'
+
+describe Mutant::Mutator::Node::Connective::Binary, 'mutations' do
+  context 'and' do
+    let(:source) { 'true and false' }
+
+    let(:mutations) do
+      mutations = []
+      mutations << 'nil'
+      mutations << 'true'
+      mutations << 'false'
+
+      mutations << 'true or false'
+
+      mutations << 'false and false'
+      mutations << 'true and true'
+
+      mutations << 'nil and false'
+      mutations << 'true and nil'
+    end
+
+    it_should_behave_like 'a mutator'
+  end
+
+  context 'or' do
+    let(:source) { 'true or false' }
+
+    let(:mutations) do
+      mutations = []
+      mutations << 'nil'
+      mutations << 'true'
+      mutations << 'false'
+
+      mutations << 'true and false'
+
+      mutations << 'false or false'
+      mutations << 'true or true'
+
+      mutations << 'nil or false'
+      mutations << 'true or nil'
+    end
+
+    it_should_behave_like 'a mutator'
+  end
+end