adder0-with-spy.rb

class Logger
  attr_reader :log_output
  def info(s)
    @log_output ||= ""
    @log_output << s << "\n"
  end
end

examples.each do |example|
  a, b, c, s = example
  # Getting a fresh Logger because it has state now
  logger = Logger.new                                # setup
  half_adder = HalfAdder.new(a, b, logger)           # setup
  half_adder.compute                                 # exercise
  assert_equality(example, half_adder.carry, c)      # verify
  assert_equality(example, half_adder.sum, s)        # verify
  adder = nil                                        # teardown
end

# And now I'm going to verify the DOC with the spy
a, b, c, s = examples[0]
expected_logging = <<LOG
augend: 0
addend: 0
carry:  0
sum:    0
LOG
logger = Logger.new                                      # 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