adds answer spec

spec/models/poll/answer_spec.rb

@@ -0,0 +1,16 @@
+require 'rails_helper'
+
+describe Poll::Answer do
+
+  describe "validations" do
+    it "validates that the answers are included in the Poll::Question's list" do
+      q = create(:poll_question, valid_answers: 'One, Two, Three')
+      expect(build(:poll_answer, question: q, answer: 'One')).to be_valid
+      expect(build(:poll_answer, question: q, answer: 'Two')).to be_valid
+      expect(build(:poll_answer, question: q, answer: 'Three')).to be_valid
+
+      expect(build(:poll_answer, question: q, answer: 'Four')).to_not be_valid
+    end
+  end
+
+end