Implement `ask' recipe keyword

spec/producer/core/prompter_spec.rb

@@ -0,0 +1,41 @@
+require 'spec_helper'
+
+module Producer::Core
+  describe Prompter do
+    let(:input)         { StringIO.new }
+    let(:output)        { StringIO.new }
+    let(:env)           { Env.new(input: input, output: output) }
+    subject(:prompter)  { Prompter.new(input, output) }
+
+    describe '#initialize' do
+      it 'assigns the given input' do
+        expect(prompter.input).to be input
+      end
+
+      it 'assigns the given output' do
+        expect(prompter.output).to be output
+      end
+    end
+
+    describe '#prompt' do
+      let(:question)  { 'Which letter?' }
+      let(:choices)   { %w[A B] }
+
+      it 'prompts choices' do
+        prompter.prompt question, choices
+        expect(output.string).to eq <<-eoh.gsub /^\s+\|/, ''
+          |#{question}
+          |0: A
+          |1: B
+          |Choice:
+        eoh
+      end
+
+      it 'returns value for entry chosen by user' do
+        input.puts '1'
+        input.rewind
+        expect(prompter.prompt question, choices).to eq 'B'
+      end
+    end
+  end
+end