adder0-with-spy-leveraging-logger.rb

require 'logger'
def get_logger
  logger = Logger.new(STDOUT)
  def logger.info(s)
    @log_output ||= ""
    @log_output << s << "\n"
  end
  def logger.log_output
    @log_output
  end
  logger
end

a, b, c, s = examples[0]
expected_logging = <<LOG
augend: 0
addend: 0
carry:  0
sum:    0
LOG
logger = get_logger                                      # setup
half_adder = HalfAdder.new(a, b, logger)                 # setup
half_adder.compute                                       # exercise
assert_equality("verifying logging",
  logger.log_output,
  expected_logging)                                      # verify
adder = nil                                              # teardown