Execute code at end of Module/Class, like Ruby test/unit

Ruby's unit testing framework executes unit tests even though nobody creates unit test object. For example,

in MyUnitTest.rb

require 'test/unit'

class MyUnitTest < Test::Unit::TestCase
    def test_true
        assert true
    end
end

and when i invoke that script as

ruby MyUnitTest.rb

test_true method gets executed automatically. How is this done?

I am trying to come up with a framework that can do similarly. I dont want "if __ FILE __ == $0" at the end of every module that uses my framework.

thanks.

From stackoverflow

• Test::Unit uses at_exit for this, which runs code immediately before your application quits:

  at_exit do
    puts "printed before quit"
  end
  
  .. other stuff
  

  I don't think there is any way to run code specifically after a class or module definition is closed.

  rampion : but you can redefine `Class.inherited` for your class to get references to all the subclasses, and then play with them in your `at_exit` hook.

• Similar to Daniel Lucraft's answer, you could define a finalizer guard to have some code run when the garbage collector runs:

  ObjectSpace.define_finalizer(MyClass, lambda {
    puts "printed before MyClass is removed from the Object space"
  })
  

  But personally I think at_exit is a better fit since its timing is a bit more deterministic.