test_helper.rb

class Test::Unit::TestCase # Or ActiveSupport::TestCase if you are using Rails
  # This is a debugging utility to find slow tests.
  # Usage: rake FIND_SLOW_TESTS=true test:units
  unless ENV["FIND_SLOW_TESTS"].blank?
    alias_method :old_run, :run
      def run(*args, &block)
        start_time = Time.now
        old_run *args, &block
        test_time = Time.now - start_time
        puts "\nSLOW TEST: #{self.name}, #{test_time}s" if test_time > 0.5
      end
  end
end