Add Mutant::NodeHelpers#n_not

lib/mutant/node_helpers.rb

@@ -27,5 +27,17 @@ module Mutant
     N_NIL             = s(:nil)
     N_EMPTY           = s(:empty)
 
+    # Build a negated boolean node
+    #
+    # @param [Parser::AST::Node] node
+    #
+    # @return [Parser::AST::Node]
+    #
+    # @api private
+    #
+    def n_not(node)
+      s(:send, node, :!)
+    end
+
   end # NodeHelpers
 end # Mutant

spec/unit/mutant/node_helpers/n_not_spec.rb

@@ -0,0 +1,12 @@
+require 'spec_helper'
+
+describe Mutant::NodeHelpers, '#n_not' do
+  subject { object.n_not(node) }
+
+  let(:object) { Object.new.extend(described_class) }
+  let(:node)   { described_class::N_TRUE            }
+
+  it 'returns the negated node' do
+    expect(subject).to eq(parse('not true'))
+  end
+end