[FEATURE] Allow parameterisation of the boolean grammar

lib/ruby_speech/grxml/builtins.rb

@@ -2,19 +2,30 @@ module RubySpeech::GRXML::Builtins
   #
   # Create a grammar for interpreting a boolean response, where 1 is yes and two is no.
   #
+  # @param [Hash] options Options to parameterize the grammar
+  # @option options [#to_s] :y The positive/truthy/affirmative digit
+  # @option options [#to_s] :n The negative/falsy digit
+  #
   # @return [RubySpeech::GRXML::Grammar] a grammar for interpreting a boolean response.
   #
-  def self.boolean
+  # @raise [ArgumentError] if the :y and :n options are the same
+  #
+  def self.boolean(options = {})
+    truthy_digit = (options[:y] || '1').to_s
+    falsy_digit = (options[:n] || '2').to_s
+
+    raise ArgumentError, "Yes and no values cannot be the same" if truthy_digit == falsy_digit
+
     RubySpeech::GRXML.draw mode: :dtmf, root: 'boolean' do
       rule id: 'boolean', scope: 'public' do
         one_of do
           item do
             tag { 'true' }
-            '1'
+            truthy_digit
           end
           item do
             tag { 'false' }
-            '2'
+            falsy_digit
           end
         end
       end

spec/ruby_speech/grxml/builtins_spec.rb

@@ -10,6 +10,23 @@
     it { should not_match('0') }
     it { should not_match('3') }
     it { should not_match('10') }
+
+    context "with the true/false digits parameterized" do
+      subject { described_class.boolean y: 3, n: 7 }
+
+      it { should max_match('3').and_interpret_as('true') }
+      it { should max_match('7').and_interpret_as('false') }
+
+      it { should not_match('1') }
+      it { should not_match('2') }
+      it { should not_match('4') }
+
+      context "both the same" do
+        it "should raise ArgumentError" do
+          expect { described_class.boolean y: '1', n: 1 }.to raise_error(ArgumentError, /same/)
+        end
+      end
+    end
   end
 
   describe "currency" do