How to test monkey patching code?

Ruby
1

Hi, all!

I’m wondering how to test some monkey patching code. Take the standard
library ‘jcode’
in Ruby 1.8 for example. It do some monkey patching for the core
String class when I
require it. If I want to write some unit-test or spec for it, how to
avoid it from affecting other
tests? In other words, how can I “uninstall” those monkey patching
after the test case
is finished or how can I constrain the monkey patching inside a …,
say, namespace?

I tried the following code:

orig_string = Object::String.clone

$KCODE = 'u'
require 'jcode'

# do testings

Object::String = orig_string

str1 = "foo"
str2 = String.new("foo")

# jlength are monkey patching
puts str1.jlength # => 3
puts str2.jlength # => raise NoMethodError

As I expected, str2.jlength raises NoMethodError, but str1 which is
built
by a string literal, returned 3, still being patched.

Further more, when I type those code directly in IRB, the irb fire out
some exception and exited immediately:

C:/ruby/lib/ruby/1.8/irb/ruby-token.rb:101:in Token': undefined methodancesto
rs’ for “=”:String (NoMethodError)
from C:/ruby/lib/ruby/1.8/irb/ruby-lex.rb:400:in lex_init' from C:/ruby/lib/ruby/1.8/irb/slex.rb:237:incall’
from C:/ruby/lib/ruby/1.8/irb/slex.rb:237:in match_io' from C:/ruby/lib/ruby/1.8/irb/slex.rb:222:inmatch_io’
from C:/ruby/lib/ruby/1.8/irb/slex.rb:76:in match' from C:/ruby/lib/ruby/1.8/irb/ruby-lex.rb:287:intoken’
from C:/ruby/lib/ruby/1.8/irb/ruby-lex.rb:263:in lex' from C:/ruby/lib/ruby/1.8/irb/ruby-lex.rb:234:ineach_top_level_stateme
nt’
from C:/ruby/lib/ruby/1.8/irb/ruby-lex.rb:230:in loop' from C:/ruby/lib/ruby/1.8/irb/ruby-lex.rb:230:ineach_top_level_stateme
nt’
from C:/ruby/lib/ruby/1.8/irb/ruby-lex.rb:229:in catch' from C:/ruby/lib/ruby/1.8/irb/ruby-lex.rb:229:ineach_top_level_stateme
nt’
from C:/ruby/lib/ruby/1.8/irb.rb:146:in eval_input' from C:/ruby/lib/ruby/1.8/irb.rb:70:instart’
from C:/ruby/lib/ruby/1.8/irb.rb:69:in catch' from C:/ruby/lib/ruby/1.8/irb.rb:69:instart’
from C:/ruby/bin/irb:13

I suppose IRB itself is doing some monkey patching to String? So, is
there any
way to …, return to my original question, to test monkey patching
code?

Thanks!

2

On Feb 7, 2008 2:59 PM, pluskid [email protected] wrote:

is finished or how can I constrain the monkey patching inside a …,
# do testings

Object::String = orig_string

I would try

 orig_string = Object::String
 Object::String = Object::String.clone

 require 'jcode'

 # do testings

 Object::String = orig_string

instead.

Ie, let the modifications happen to a clone, rather than the original.
That might stop “” from generating a monkey-patched string during
testing, though.

Eivind.