Clean up spurious JSON decoding test failure

activesupport/lib/active_support/json/backends/jsongem.rb

@@ -2,10 +2,9 @@ require 'json' unless defined?(JSON)
 
 module ActiveSupport
   module JSON
-    ParseError = ::JSON::ParserError unless const_defined?(:ParseError)
-
     module Backends
       module JSONGem
+        ParseError = ::JSON::ParserError
         extend self
 
         # Parses a JSON string or IO and convert it into an object
@@ -38,4 +37,4 @@ module ActiveSupport
       end
     end
   end
-end
+end

activesupport/lib/active_support/json/backends/yaml.rb

@@ -2,13 +2,9 @@ require 'active_support/core_ext/string/starts_ends_with'
 
 module ActiveSupport
   module JSON
-    unless const_defined?(:ParseError)
-      class ParseError < StandardError
-      end
-    end
-
     module Backends
       module Yaml
+        ParseError = ::StandardError
         extend self
 
         # Parses a JSON string or IO and converts it into an object

activesupport/lib/active_support/json/decoding.rb

@@ -7,6 +7,7 @@ module ActiveSupport
 
   module JSON
     class << self
+      attr_reader :parse_error
       delegate :decode, :to => :backend
 
       def backend
@@ -21,6 +22,7 @@ module ActiveSupport
           require "active_support/json/backends/#{name.to_s.downcase}.rb"
           @backend = ActiveSupport::JSON::Backends::const_get(name)
         end
+        @parse_error = @backend::ParseError
       end
 
       def with_backend(name)

activesupport/test/json/decoding_test.rb

@@ -47,13 +47,7 @@ class TestJSONDecoding < ActiveSupport::TestCase
   ActiveSupport::JSON.backend
 
   backends = %w(Yaml)
-  begin
-    gem 'json', '>= 1.1'
-    require 'json'
-    backends << "JSONGem"
-  rescue Gem::LoadError
-    # Skip JSON gem tests
-  end
+  backends << "JSONGem" if defined?(::JSON)
 
   backends.each do |backend|
     TESTS.each do |json, expected|
@@ -81,7 +75,7 @@ class TestJSONDecoding < ActiveSupport::TestCase
   end
 
   def test_failed_json_decoding
-    assert_raise(ActiveSupport::JSON::ParseError) { ActiveSupport::JSON.decode(%({: 1})) }
+    assert_raise(ActiveSupport::JSON.parse_error) { ActiveSupport::JSON.decode(%({: 1})) }
   end
 end