diff --git a/lib/rabl-rails/renderer.rb b/lib/rabl-rails/renderer.rb
index 2a04493..168b409 100644
--- a/lib/rabl-rails/renderer.rb
+++ b/lib/rabl-rails/renderer.rb
@@ -28,7 +28,7 @@ module RablRails
     end
 
     #
-    # Context class to emulate normal rendering view
+    # Context class to emulate normal Rails view
     # context
     #
     class Context
@@ -66,6 +66,16 @@ module RablRails
     # Default render format is JSON, but can be changed via
     # an option: { format: 'xml' }
     #
+    # If template includes uses of instance variables (usually 
+    # defined in the controller), you can passed them as locals
+    # options.
+    # For example, if you have this template:
+    #   object :@user
+    #   node(:read) { |u| u.has_read?(@post) }
+    #
+    # Your method call should look like this:
+    #   RablRails.render(user, 'users/show', locals: { post: Post.new })
+    #
     def render(object, template, options = {})
       object = options[:locals].delete(:object) if !object && options[:locals]
 
diff --git a/test/render_test.rb b/test/render_test.rb
index c9dd417..8108f7c 100644
--- a/test/render_test.rb
+++ b/test/render_test.rb
@@ -17,7 +17,6 @@ class RenderTest < ActiveSupport::TestCase
         attributes :name
       }
     end
-
     assert_equal %q({"user":{"name":"Marty"}}), RablRails.render(nil, 'nil', locals: { object: @user }, view_path: @tmp_path)
   end
 
@@ -28,12 +27,21 @@ class RenderTest < ActiveSupport::TestCase
         attributes :id, :name
       }
     end
-
     assert_equal %q({"user":{"id":1,"name":"Marty"}}), RablRails.render(@user, 'show', view_path: @tmp_path)
   end
   
   test "raise error if template is not found" do
-    assert_raises(RablRails::Renderer::TemplateNotFound) { RablRails.render(@user, 'show') }
+    assert_raises(RablRails::Renderer::TemplateNotFound) { RablRails.render(@user, 'not_found') }
+  end
+  
+  test "instance variables can be passed via options[:locals]" do
+    File.open(@tmp_path + "instance.json.rabl", "w") do |f|
+      f.puts %q{
+        object false
+        node(:username) { |_| @user.name } 
+      }
+    end
+    assert_equal %q({"username":"Marty"}), RablRails.render(nil, 'instance', view_path: @tmp_path, locals: { user: @user })
   end
 
   test "handle path for extends" do
@@ -43,7 +51,7 @@ class RenderTest < ActiveSupport::TestCase
         extends 'base'
       }
     end
-
+    
     File.open(@tmp_path + "base.json.rabl", "w") do |f|
       f.puts %q{
         attribute :name, as: :extended_name