output

[..inator/ruby-hashdec/tests]$ ./trace.rb 
Entering test(1)
In test()
Leaving test (returned nil)
[..inator/ruby-hashdec/tests]$ 

trace.rb

#!/usr/bin/env ruby

require '../lib/hashdec.rb'

# FIXME: Make it work with test(*args)

module HashDec
  def self.trace(ba, function, hashdec_args, args, ret)
    case ba
    when :before
      puts "Entering #{function}(#{args.map(&:inspect).join(', ')})"
    when :after
      puts "Leaving #{function} (returned #{ret.inspect})"
    end
  end
end

#trace()
def test(arg)
  puts "In test()"
end

test 1