Require to execute

Have you ever wondered, how it works, that by simply putting something like …

---

require 'test/unit'

class MyTest < Test::Unit::TestCase

	def test_sample

		assert(false,";)")

	end

end

… you can make a unit test in ruby and simply call that file and everything works? Coming from Java I first thought, perhaps also Ruby classes get have some main methods in them to trigger execution if really nothing else is there in the main-scope to execute. But then I found this code in the test/unit.rb:

at_exit do

  unless $! || Test::Unit.run?

    exit Test::Unit::AutoRunner.run

  end

end

And yes: at_exit {block} is actually something like that. You can register there things that should be run when the main-scope exits. Sweet :)