From: Brian Candler <B.Candler@...>
Date: 2005-03-19T20:15:09+09:00
Subject: Test::Unit teardown with child process

I have a suggestion which might improve the behaviour of the 'teardown'
facility in Test::Unit.

I had a problem where my tests were being torn down prematurely, which took
some hunting around to find. It turned out that it was because my tests were
forking a child process using IO.popen, and when the child terminated, the
teardown was being called. The test script attached below demonstrates this.

I can work around it like this:

class MyTest < Test::Unit::TestCase

  BASEPID = $$

  def teardown
    # If we are a child process exiting, don't do any teardown
    return unless BASEPID == $$

    .. do stuff
  end
end

But I think it would be nice if the Test::Unit infrastructure could take
care of that, i.e. only call the teardown methods if the current pid is the
same as the pid when the 'setup' method was called.

However, I have to say I don't understand this entirely. If I fork a child
using Process.fork then the child's termination *doesn't* cause the teardown
to be called - see method test2 in the attached script.

Any ideas why test1 and test2 should be different in this regard?

Regards,

Brian.
-------------------------------------------------------------------------
require 'test/unit'

class MyTest < Test::Unit::TestCase

  def setup
    $stderr.puts "setup #{$$}"
    File.open("xxx","w") { |f| f.puts "testdata" }
  end

  def teardown
    $stderr.puts "teardown #{$$}"
    File.delete("xxx")
  end

  # This test fails; teardown is called prematurely

  def test1
    res = nil
    IO.popen("-") do |pipe|
      if pipe
        res = pipe.read
      else
        puts "hello"
        exit 0
      end
    end
    assert_match(/hello/, res, "child status")

    data = nil
    File.open("xxx") { |f| data = f.read }
    assert_match(/testdata/, data)
  end

  # Strangely, this test succeeds

  def test2
    pid = Process.fork do
      puts "Child OK #{$$}"
      exit 0
    end
    dummy, status = Process.waitpid2(pid)
    assert_equal(pid, dummy, "correct pid")
    assert_equal(0, status.exitstatus, "correct exit status")

    sleep 1
    data = nil
    File.open("xxx") { |f| data = f.read }
    assert_match(/testdata/, data)
  end
end