Macros for adding setup and teardown to a context don't do what I think they should

shoulda_context_test.rb

require 'test_helper'

class ShouldaContextTest < ActiveSupport::TestCase
  def self.setup_setup_helper
    setup { puts "running the setup helper"; @wrapped = true }
    teardown{ puts "running the teardown helper"; @wrapped = false }
  end
  context "outer nesting" do
    context "without setup" do
      setup do
        puts "inner explicit setup"
      end
      should 'not have run the other setup' do
        puts "non-setup assertion"
        assert !@wrapped
      end
    end
    context 'irrelevant' do
      setup_setup_helper
      should 'not matter' do
        puts "setup assertion"
        assert @wrapped
      end
    end
  end
end

test output

$ time bundle exec ruby -Itest test/unit/shoulda_context_test.rb 
WebMock disabling network connections (use SKIP_WEBMOCK to disable)
Loaded suite test/unit/shoulda_context_test
Started
running the setup helper
setup assertion
running the teardown helper
running the setup helper
inner explicit setup
non-setup assertion
F
===============================================================================
Failure: <false> is not true.
test: outer nesting without setup should not have run the other setup. (ShouldaContextTest)
test/unit/shoulda_context_test.rb:15:in `block (3 levels) in <class:ShouldaContextTest>'
===============================================================================
running the teardown helper


Finished in 0.934133 seconds.

2 tests, 3 assertions, 1 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
0% passed

2.14 tests/s, 3.21 assertions/s

real	0m16.799s
user	0m8.270s
sys	0m3.669s