diff --git a/test/ripper.rb b/test/ripper.rb
new file mode 100644
index 0000000..44b643c
--- /dev/null
+++ b/test/ripper.rb
@@ -0,0 +1,103 @@
+require 'ripper'
+require 'pp'
+require 'byebug'
+
+class DemoBuilder < Ripper::SexpBuilder
+  def initialize(*args)
+    super(*args)
+    @errors = []
+    @identifiers = []
+    @arguments = []
+  end
+
+  events = private_instance_methods(false).grep(/\Aon_/) {$'.to_sym}
+  (PARSER_EVENTS - events).each do |event|
+    module_eval(<<-End, __FILE__, __LINE__ + 1)
+      def on_#{event}(*args)
+        super.tap { |result| p result }
+      end
+    End
+  end
+
+  def on_args_new
+    []
+  end
+
+  def on_args_add(args, new_arg)
+    args << new_arg
+  end
+
+  def on_args_add_block(args, block)
+    raise NotImplementedError if block
+    args
+  end
+
+  def on_arg_paren(args)
+    "(" <<
+    args.map do |arg|
+      ttype, token = arg
+      case ttype
+      when :quantity
+        "params['#{token}']"
+      when :indexed_expr
+        # FIXME: token expression has to be evaluated in block with _index and
+        # result stored in @arguments
+        @arguments << token
+        "args['#{@arguments.length - 1}']"
+      else
+        raise NotImplementedError
+      end
+    end.join(',') <<
+    ")"
+  end
+
+  #def on_call(left, dot, right)
+  #  "#{left}#{dot}#{right}"
+  #end
+  
+  #def on_method_add_arg(method, arg)
+  #  "#{method}#{arg}"
+  #end
+
+  def on_binary(left, op, right)
+    [
+      :indexed_expr,
+      [left, right].map do |side|
+        side[0] == :quantity ? "params['#{side[1]}'][_index]" : "#{side[1]}"
+      end.join(op.to_s)
+    ]
+  end
+
+  def on_var_ref(var_ref)
+    ttype, name = var_ref
+    if ttype == :quantity_name
+      [:quantity, name] 
+    else
+      raise NotImplementedError
+    end
+  end
+
+  SCANNER_EVENTS.each do |event|
+    module_eval(<<-End, __FILE__, __LINE__ + 1)
+      def on_#{event}(tok)
+        super.tap { |result| p result }
+        #super
+      end
+    End
+  end
+
+  def on_const(token)
+    @identifiers << token
+    [:quantity_name, token]
+  end
+
+  def on_ident(token)
+    token
+  end
+end
+
+#src = "1 + 1"
+src = "(Weight/Height.all(3*Dupa).lastBefore(TakenAt)^2) + 2*Other*Other"
+#src = "a = 2; b = a"
+pp DemoBuilder.new(src).parse
+pp Ripper.sexp_raw(src)