Use explicit error

lib/rabl-fast-json/renderers/base.rb

@@ -1,5 +1,7 @@
 module RablFastJson
   module Renderers
+    class PartialError < StandardError; end
+
     class Base
 
       def initialize(context) # :nodoc:
@@ -79,7 +81,7 @@ module RablFastJson
       # rendering time.
       #
       def partial(template_path, options = {})
-        raise "No object was given to partial" unless options[:object]
+        raise PartialError.new("No object was given to partial") unless options[:object]
         object = options[:object]
 
         return [] if object.respond_to?(:empty?) && object.empty?

test/renderers/json_renderer_test.rb

@@ -98,7 +98,7 @@ class TestJsonRenderer < ActiveSupport::TestCase
     @template.data = false
     @template.source = { :user => ->(s) { partial('users/base') } }
 
-    assert_raises(RuntimeError) { render_json_output }
+    assert_raises(RablFastJson::Renderers::PartialError) { render_json_output }
   end
 
   test "partial with empty values should not raise an error" do