some ruby interpreters don't have ruby-prof so just skip the tests

rather than exiting the process.

activesupport/lib/active_support/testing/performance/ruby.rb

@@ -2,7 +2,7 @@
   require 'ruby-prof'
 rescue LoadError
   $stderr.puts 'Specify ruby-prof as application\'s dependency in Gemfile to run benchmarks.'
-  exit
+  raise
 end
 
 module ActiveSupport

activesupport/test/testing/performance_test.rb

 require 'abstract_unit'
-require 'active_support/testing/performance'
-
 
 module ActiveSupport
   module Testing
     class PerformanceTest < ActiveSupport::TestCase
+      begin
+        require 'active_support/testing/performance'
+        HAVE_RUBYPROF = true
+      rescue LoadError
+        HAVE_RUBYPROF = false
+      end
+
+      def setup
+        skip "no rubyprof" unless HAVE_RUBYPROF
+      end
+
       def test_amount_format
         amount_metric = ActiveSupport::Testing::Performance::Metrics[:amount].new
         assert_equal "0", amount_metric.format(0)
@@ -56,4 +65,4 @@ def test_environment_format_with_rails
       end
     end
   end
-end
\ No newline at end of file
+end