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

spec/producer/core/task/dsl_spec.rb

@@ -3,7 +3,7 @@ require 'spec_helper'
 module Producer::Core
   describe Task::DSL do
     let(:block)   { proc {} }
-    let(:env)     { double 'env' }
+    let(:env)     { Env.new }
     subject(:dsl) { Task::DSL.new(env, &block) }
 
     %w[echo sh file_write].each do |action|
@@ -82,5 +82,25 @@ module Producer::Core
         end
       end
     end
+
+    describe '#ask' do
+      let(:question)        { 'Which letter?' }
+      let(:choices)         { %w[A B] }
+      let(:prompter_class)  { double('prompter class').as_null_object }
+      subject(:ask)         { dsl.ask question, choices,
+                              prompter: prompter_class }
+
+      it 'builds a prompter' do
+        expect(prompter_class).to receive(:new).with(env.input, env.output)
+        ask
+      end
+
+      it 'prompts and returns the choice' do
+        prompter = double 'prompter'
+        allow(prompter_class).to receive(:new) { prompter }
+        allow(prompter).to receive(:prompt) { :choice }
+        expect(ask).to eq :choice
+      end
+    end
   end
 end