adds author_of? helper method

app/helpers/application_helper.rb

@@ -35,4 +35,9 @@ module ApplicationHelper
     }
     Redcarpet::Markdown.new(renderer, extensions).render(text).html_safe
   end
+
+  def author_of?(authorable, user)
+    return false if authorable.blank? || user.blank?
+    authorable.author_id == user.id
+  end
 end

spec/helpers/application_helper_spec.rb

@@ -0,0 +1,27 @@
+require 'rails_helper'
+
+describe ApplicationHelper do
+
+  describe "#author_of?" do
+    it "should be true if user is the author" do
+      user = create(:user)
+      proposal = create(:proposal, author: user)
+      expect(author_of?(proposal, user)).to eq true
+    end
+
+    it "should be false if user is not the author" do
+      user = create(:user)
+      proposal = create(:proposal)
+      expect(author_of?(proposal, user)).to eq false
+    end
+
+    it "should be false if user or authorable is nil" do
+      user = create(:user)
+      proposal = create(:proposal)
+
+      expect(author_of?(nil, user)).to eq false
+      expect(author_of?(proposal, nil)).to eq false
+    end
+  end
+
+end