adder0-with-logger-and-stub.rb

class HalfAdder
  attr_reader :sum, :carry

  def initialize(augend, addend, logger)
    @augend, @addend, @logger = augend, addend, logger
  end

  def compute
    @carry = @augend & @addend
    @sum = @augend ^ @addend
    @logger.info "augend: #{@augend}"
    @logger.info "addend: #{@addend}"
    @logger.info "carry:  #{@carry}"
    @logger.info "sum:    #{@sum}"
  end
end

def assert_equality(example, actual, expected)
  print "example #{example}: "
  if actual == expected
    puts 'Pass'
  else
    puts "Fail: got #{actual.inspect}; expected #{expected.inspect}"
  end
end

examples = [
  [0, 0, 0, 0],
  [1, 0, 0, 1],
  [0, 1, 0, 1],
  [1, 1, 1, 0]
]

class Stub
  def info(*)
  end
end
stub = Stub.new

examples.each do |example|
                                                     # The 4 phases: seup, exercise, verify, teardown
  a, b, c, s = example                               # setup
  half_adder = HalfAdder.new(a, b, stub)             # 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