Minitest stubbing is weird

retry.rb

require "minitest/autorun"

class Something
  def dont_do_it
    :oops
  end
end

class RetryTest < Minitest::Test
  def test_different_return_values
    thing   = Something.new
    results = [42, RuntimeError.new("Boom!")]
    body    = -> {
      result = results.shift
      result.is_a?(Exception) ? raise(result) : result
    }
    thing.stub(:dont_do_it, body) do
      assert_equal(42, thing.dont_do_it)
      assert_raises(RuntimeError) do
        thing.dont_do_it
      end
    end
  end
end