bar.rb

p "in bar.rb"

foo.rb

sleep 10

require_test.rb

$: << "."

th1 = Thread.start do
  p "before require foo"
  require "foo"
  p "after require foo"
end
until th1.status == "sleep"
  Thread.pass
end

p "before require bar"
require "bar"
p "after require bar"
th1.join