foo.rb

class Test::Unit::TestCase
  def self.setup(&block)
    include module_with_callback(:setup, &block)
  end

  def self.teardown(&block)
    include module_with_callback(:teardown, &block)
  end

  def self.global_setup(&block)
    include module_with_callback(:global_setup, &block)
  end

  def self.global_teardown(&block)
    include module_with_callback(:global_teardown, &block)
  end

  class << self
    alias_method :before,     :setup
    alias_method :after,      :teardown
    alias_method :before_all, :global_setup
    alias_method :after_all,  :global_teardown
  end

  def setup
    unless @__global_setup_run
      @__global_setup_run = true
      global_setup
    end
  end

  def teardown
    unless @__global_teardown_run
      @__global_teardown_run = true
      global_teardown
    end
  end

  def global_setup; end
  def global_teardown; end

  def self.module_with_callback(name, &block)
    Module.new { define_method(name, &block) }
  end
end